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Username Post: 1989 Chevy 305 TBI pinging
VintageCarryall
Frequent Contributor
Posts 2249
06-02-09 07:34 PM - Post#1709982    

I have a 1989 Chevy Caprice sedan with a 305 TBI/700R4 drivetrain.

The main problem is a definite pinging under either steady speed driving and/or light acceleration.

I pulled the EGR valve off and the car started/idled fine (?). I did pop the TBI censored'y off as well and squirted carb cleaner through the twin horizontal slots just under the throttle bores. There was a slight dribble of fluid through the passages indicating they are not totally blocked.

Put everything back together; verified ignition timing (it is correct) and the engine still pings. Any ideas?

Side note: the catalyst was absolutely gutted (unknown of someone went there and or the substrate was simply burned out). Slapped a new cat (called for a 3 way) as well as had the return line @ the fuel sending unit soldered up so the car would pass the IM test here in the Phx area.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Boosted 1
Member
Posts 179
06-02-09 11:11 PM - Post#1710062    

Kinda vague on the info, but try some good fuel,or if this has a lot of miles on it, or if there was a problem with the fuel system at one time (maybe way the cat was removed) you could try SPRAYING water down through the throttle body while it is running at about 1500 rpm to clean the carbon off the top of the pistons
92 3500 toy hauler, 63,70,Nova,83 Shovel, Blown with N2o 90 step side

bowtie67
Senior Member
Posts 658
06-03-09 03:28 AM - Post#1710106    

The engine is probably carboned up, try seafoaming the engine before replacing things, also the possiblity of some bad gas.
VintageCarryall
Frequent Contributor
Posts 2249
06-03-09 05:38 AM - Post#1710157    

  • bowtie67 Said:
The engine is probably carboned up, try seafoaming the engine before replacing things, also the possiblity of some bad gas.



Two tanks of regular gas thus far; I am going to try some premium next time I fill the car.

Vehicle used to be a taxicab so the carboned up part is plausible.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Twilightoptics
Senior Member
Posts 760
Twilightoptics
06-03-09 06:40 AM - Post#1710194    

While Taxis do seem to idle around alot, the ones I've riden in have seen plenty RPM's to clean out that carbon!

I'd think about having the engine motorvaced. Some mid 80's 305s hate 87 octane and some are okay with it. You might also try a cooler thermostat.
'87 IROC-Z 355 HSR C950 Lunati Voodoo Solid 241/249@.050 .555/.576 lift(1.6) 110LSA, Pro Topline Iron 200cc/64cc, T56
'04 Jeep Wrangler "Rocky Mountain" 4.0L/5spd
'82 RX-7 GSL

Scotts
Frequent Contributor
Posts 1045
Scotts
06-03-09 06:44 AM - Post#1710197    

  • VintageCarryall Said:
I pulled the EGR valve off and the car started/idled fine (?).



Do you mean the vacuum line OR EGR itself. With the EGR removed, you should have had a gross vacuum leak, something the engine didn't like. If it didn't the EGR port is plugged it will contribute/cause detonation. If it was just the vacuum line, the EGR has no function at idle...

  • VintageCarryall Said:

Put everything back together; verified ignition timing (it is correct) and the engine still pings.



Did you disconnect the timing connector to the ecm when performing timing check - common mistake.

Carbon build up would be plausible but if the EGR is not functioning, depending on engine temp and fuel octane, it will be uphill battle. A non-functioning EGR system will enhance carbon build up symptoms...
NO WARRANTY EXPRESSED OR IMPLIED! I may be wrong, have in the past and will be in the future!

VintageCarryall
Frequent Contributor
Posts 2249
06-03-09 07:12 PM - Post#1710639    

  • Scotts Auto Said:
  • VintageCarryall Said:
I pulled the EGR valve off and the car started/idled fine (?).



Do you mean the vacuum line OR EGR itself. With the EGR removed, you should have had a gross vacuum leak, something the engine didn't like. If it didn't the EGR port is plugged it will contribute/cause detonation. If it was just the vacuum line, the EGR has no function at idle...

  • VintageCarryall Said:

Put everything back together; verified ignition timing (it is correct) and the engine still pings.



Did you disconnect the timing connector to the ecm when performing timing check - common mistake.

Carbon build up would be plausible but if the EGR is not functioning, depending on engine temp and fuel octane, it will be uphill battle. A non-functioning EGR system will enhance carbon build up symptoms...



With the EGR valve removed from the intake; the car idled fine. Needless to say, I was finally able to 'hog out' the little passage just below the TBI/intake interface that led to the EGR valve. It was quite plugged up.

The pinging is all but gone but I have a new problem-------the car has a strong stumble off idle and 'stutters' since the EGR is now working (I depressed the diaphragm by hand and the engine stalled out immediately).

Timing: I checked it with the black/brown connector disconnected...........it was at TDC as specified.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


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Posts 179
06-03-09 09:37 PM - Post#1710709    

Just a shot in the dark, but if you have a Lab-Scope check TPS for drop-outs
92 3500 toy hauler, 63,70,Nova,83 Shovel, Blown with N2o 90 step side

Scotts
Frequent Contributor
Posts 1045
Scotts
06-03-09 10:56 PM - Post#1710729    

Remove battery cable for a bit, take it out and drive - allow ecm to relearn...

Check for codes after reset / relearn if problem persists.
NO WARRANTY EXPRESSED OR IMPLIED! I may be wrong, have in the past and will be in the future!

bowtie67
Senior Member
Posts 658
06-04-09 03:55 AM - Post#1710769    

If the EGR system was quite plugged it basically means the engine basically is carboned up, running premium fuel will not undo the carbon build up right away nor will going out and hammering the daylights out of it, you may get some of it out of the engine but a lot will stay there.
revheadgl
Contributor
Posts 461
revheadgl
06-04-09 04:09 AM - Post#1710780    

A carbonned up motor is frankly in need of a rebuild. There are no simple fixes.

Not meaning to be rude or offensive, but it is what it is. Worn out and carbonned up.

If indeed that is the case with your motor.
67 Falcon 289, Weiand 174 @ 8.5 psi boost,
Edelbrock Performer RPM Heads, 216/228 0.483/0.480 0.050 112 degrees LSA. Forged pistons 9.0-1, Holley 950-24s system, Ford TFI, Crane HI-6 & LX92.

Scotts
Frequent Contributor
Posts 1045
Scotts
06-04-09 04:22 AM - Post#1710784    

  • bowtie67 Said:
If the EGR system was quite plugged it basically means the engine basically is carboned up, nor will going out and hammering the daylights out of it, you may get some of it out of the engine but a lot will stay there.



No doubts about it - in addition, considering the constant pinging, the knock sensor would have been pulling timing constantly - it's now advancing - maybe.

It may in fact be the knock sensor causing this new issue - among other things - chunks of busted carbon in the spark plugs / electrode from cleaning the intake, etc.

  • bowtie67 Said:
The engine is probably carboned up, try seafoaming the engine before replacing things, also the possiblity of some bad gas.



Excellent idea and most beneficial!
NO WARRANTY EXPRESSED OR IMPLIED! I may be wrong, have in the past and will be in the future!

revheadgl
Contributor
Posts 461
revheadgl
06-04-09 05:11 AM - Post#1710802    

Does it ever run on after shutdown? I mean ever? Does it ever kick on just once or twice?
67 Falcon 289, Weiand 174 @ 8.5 psi boost,
Edelbrock Performer RPM Heads, 216/228 0.483/0.480 0.050 112 degrees LSA. Forged pistons 9.0-1, Holley 950-24s system, Ford TFI, Crane HI-6 & LX92.

VintageCarryall
Frequent Contributor
Posts 2249
06-04-09 06:23 AM - Post#1710849    

  • revheadgl Said:
Does it ever run on after shutdown? I mean ever? Does it ever kick on just once or twice?



No Dieseling/running on once shut off. Remember the vehicle is TBI, not carbed.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


VintageCarryall
Frequent Contributor
Posts 2249
06-04-09 06:24 AM - Post#1710850    

  • Boosted 1 Said:
Just a shot in the dark, but if you have a Lab-Scope check TPS for drop-outs



I doubt it being the driveability was perfect prior to my cleaning out the EGR passage.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


revheadgl
Contributor
Posts 461
revheadgl
06-04-09 06:35 AM - Post#1710862    

No Offence..TBI or carbed... they will still run on. Carbon is carbon. MPFI will run on as well when the motor is clapped out. Worn is worn.
67 Falcon 289, Weiand 174 @ 8.5 psi boost,
Edelbrock Performer RPM Heads, 216/228 0.483/0.480 0.050 112 degrees LSA. Forged pistons 9.0-1, Holley 950-24s system, Ford TFI, Crane HI-6 & LX92.

Twilightoptics
Senior Member
Posts 760
Twilightoptics
06-04-09 06:48 AM - Post#1710877    

Try the seafoam.

At very least pull the intake and clean the EGR passages thoroughly, and clean the passages in the head.
'87 IROC-Z 355 HSR C950 Lunati Voodoo Solid 241/249@.050 .555/.576 lift(1.6) 110LSA, Pro Topline Iron 200cc/64cc, T56
'04 Jeep Wrangler "Rocky Mountain" 4.0L/5spd
'82 RX-7 GSL

hoppycamaro
Forum Newbie
Posts 34
hoppycamaro
06-04-09 04:45 PM - Post#1711239    

knowone elce has asked so i will, what is the mechanical state of the engine, is it worn out? A 1989 taxi would have alot of hard intown miles. mabe check compression douse it use or burn oil. exesive amounts of oil in the cyleinders will cause pinging. if the engine is in sound mechanical order then start by cleaning out carbon with whatever methed you like best.
jason
VintageCarryall
Frequent Contributor
Posts 2249
06-04-09 06:13 PM - Post#1711295    

UPDATE:

The driveability tech at work scanned the engine computer and it states that the car only has about 10" of vacuum-----------never mind according to a vacuum gauge it is pulling ca. 21 inches at idle.

On a hunch, I replaced the MAP sensor----------no difference so we are now thinking the actual computer is at fault.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Twilightoptics
Senior Member
Posts 760
Twilightoptics
06-04-09 06:15 PM - Post#1711296    

What is the reading of the map sensor in KPA at idle?

Should read between 30-50kpa.

Mind you, if you have an egr leak, vacuum leak, etc something mechanical causing a rough running situation.... manifold vacuum WILL read low.
'87 IROC-Z 355 HSR C950 Lunati Voodoo Solid 241/249@.050 .555/.576 lift(1.6) 110LSA, Pro Topline Iron 200cc/64cc, T56
'04 Jeep Wrangler "Rocky Mountain" 4.0L/5spd
'82 RX-7 GSL

1983G20Van
Super Senior Member
Posts 3223
06-04-09 06:26 PM - Post#1711306    

  • revheadgl Said:
No Offence..TBI or carbed... they will still run on. Carbon is carbon. MPFI will run on as well when the motor is clapped out. Worn is worn.



Factory TBI motors will NOT run-on...Sorry.
1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals

Chevytech
Subject Matter Expert - Senior Member
Posts 3094
06-04-09 06:33 PM - Post#1711312    

  • VintageCarryall Said:
UPDATE:

The driveability tech at work scanned the engine computer and it states that the car only has about 10" of vacuum-----------never mind according to a vacuum gauge it is pulling ca. 21 inches at idle.

On a hunch, I replaced the MAP sensor----------no difference so we are now thinking the actual computer is at fault.


Check the vacuum on the port the feeds the MAP sensor. Sometimes the TBI base gasket comes apart and gets all humped up into the passage that supplies vacuum for the MAP sensor.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

VintageCarryall
Frequent Contributor
Posts 2249
06-04-09 07:20 PM - Post#1711334    

  • Chevytech Said:
  • VintageCarryall Said:
UPDATE:

The driveability tech at work scanned the engine computer and it states that the car only has about 10" of vacuum-----------never mind according to a vacuum gauge it is pulling ca. 21 inches at idle.

On a hunch, I replaced the MAP sensor----------no difference so we are now thinking the actual computer is at fault.


Check the vacuum on the port the feeds the MAP sensor. Sometimes the TBI base gasket comes apart and gets all humped up into the passage that supplies vacuum for the MAP sensor.



I had the TBI off to clear out the EGR passage. And too; the vacuum source tor the MAP was pulling ca. 21" at idle.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Scotts
Frequent Contributor
Posts 1045
Scotts
06-04-09 08:09 PM - Post#1711355    

  • VintageCarryall Said:
UPDATE:

The driveability tech at work scanned the engine computer and it states that the car only has about 10" of vacuum-----------never mind according to a vacuum gauge it is pulling ca. 21 inches at idle.

On a hunch, I replaced the MAP sensor----------no difference so we are now thinking the actual computer is at fault.




Just a thought, put a vacuum pump with gauge on the Map sensor and "scan the engine", it would take the engine out of the equation - regardless of engine temp, rpm, vacuum leak, etc. They can be purchased on the cheap from Autozone, etc?
NO WARRANTY EXPRESSED OR IMPLIED! I may be wrong, have in the past and will be in the future!

The_Hunter
Contributor
Posts 984
The_Hunter
06-04-09 08:19 PM - Post#1711362    

There's no way a fuel injected engine will run on since the power to the injectors gets cut.

Anyway, my 350 pings on me all the time too once it's full hot. I replaced the EGR valve with a new $130 Delphi or Delco valve. Fuel pressure is around 15psi. I also have H pipe 3" exhaust with dynomax ultraflow mufflers, very unrestrictive lol. I'm sure these things are working together to cause my pinging issues, hows your fuel pressure, stock exhaust? aftermarket?

I'm watching this thread with interest.
86 C10 Short Box

Computers are like air conditioners - They can't do their job properly if you open windows.

bowtie67
Senior Member
Posts 658
06-05-09 04:01 AM - Post#1711433    

  • revheadgl Said:
A carbonned up motor is frankly in need of a rebuild. There are no simple fixes.

Not meaning to be rude or offensive, but it is what it is. Worn out and carbonned up.

If indeed that is the case with your motor.



A carboned up motor does not mean it is in need of a rebuild, Carboned up motors can happen by running cheap low octane gas, excessive idling(most common), or driving like Miss daisy with Granny going to church and never really cleaning out the carbon in the motor or worse all of the above.

Ways of removing carbon can vary, If the engine is severey carboned up you will have to use heavy duty products, Seafoam Engine treatment soaks into the carbon to soften and burn it out, I have used water, transmission fluid and even GM had a product to cleanout carbon. Once cleaned and you can use a procut like Lukas Injector Cleaner it is a really good fuel additive for cleaning injectors but it also works with carbs and such, 1 bottle in a tank also helps to clean, if an existing problem exist and if you get the engine cleaned up a period bottle occasionally will keep it clean. Using high test gas will help or even sporadic tank of high test will help keep carbon to a minimum. One problem of trying to knock out the carbon with just pulling the intake but not heads is that a peice may fall into the cylinders and create an engine knock, It is usually a good idea first to run a heavy duty decarbonizing product first to at least clean cylinders and valves then pull the intake. When excessive carbon is happening the pistons tops and chambers in the heads get carboned and this increases compression and it also retains more heat in the cylinders, in some cases it can get so thick it may even cause what appears to be a rod knock. I have seen some cars so bad that the EGR was plugged solid, the PCV system was also plugged solid, the crossover passage plugged, some of this was also from extreme lack of oil changes and especially the use of parafin based oils that build up ungodly in the motor (most of these usually end up needing an engine).
VintageCarryall
Frequent Contributor
Posts 2249
06-05-09 05:26 AM - Post#1711471    

  • The_Hunter Said:
There's no way a fuel injected engine will run on since the power to the injectors gets cut.

Anyway, my 350 pings on me all the time too once it's full hot. I replaced the EGR valve with a new $130 Delphi or Delco valve. Fuel pressure is around 15psi. I also have H pipe 3" exhaust with dynomax ultraflow mufflers, very unrestrictive lol. I'm sure these things are working together to cause my pinging issues, hows your fuel pressure, stock exhaust? aftermarket?

I'm watching this thread with interest.



MY EGR valve tested good according to a vacuum pump--------and, will stall the engine immediately. Right now the electrical feed to the EGR solenoid is disconnected so I can drive the car safely since the valve is fed by manifold vacuum.

Aside from a 2 1/4" Magnaflow 3 way catalyst, the single exhaust is bone stock--------down to the smog pump lines.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Chevytech
Subject Matter Expert - Senior Member
Posts 3094
06-05-09 08:10 AM - Post#1711541    


  • VintageCarryall Said:
Right now the electrical feed to the EGR solenoid is disconnected so I can drive the car safely since the valve is fed by manifold vacuum.

Without the EGR working it is no surprise that it is pinging.
Fix the problem so you can reconnect the EGR and it may not ping at all.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

Scotts
Frequent Contributor
Posts 1045
Scotts
06-05-09 09:16 AM - Post#1711579    

  • Chevytech Said:

  • VintageCarryall Said:
Right now the electrical feed to the EGR solenoid is disconnected so I can drive the car safely since the valve is fed by manifold vacuum.

Without the EGR working it is no surprise that it is pinging.
Fix the problem so you can reconnect the EGR and it may not ping at all.




To summarize - the original complaint was pinging.

After finding the egr port plugged and cleaning it out, you developed off idle hesitation/stutter…

Your datalog/realtime readings at the ECM shows only 10" of vacuum but at the manifold its 21”.

You’re leaning towards the ECM being faulty, due to MAP sensor replacement and no change - so you disconnected the EGR valve, pinging again -back to square one?

Assumptions / questions:

Ignition, plugs, fuel pressure, compression are all good, no vacuum leaks and no codes after driving – not just reset and testing at idle or 1 mile run…

Cleaned without removing intake – may still have one bank plugged.

Allow the ECM to relearn (fuel trim /adaptive would have been changed considerably)?

Perform a vacuum test both warm and cold (worn valve guides or seats, among other things - will change vacuum readings under temp variables)?

Perform a mechanical/static/hand pump vacuum test on your map to identify where the discrepancy is between 10” at the ecm and 21” at the manifold.

Since you have the capacity to "scan the engine" - realtime I am assuming, do you have the ability to monitor the 02 fuel trim – is it calling for fuel and just not getting it – what are the cross counts – if any?

If the ecm is reading 10” of vacuum, it should be loading up plugs – have you inspected any of them?

NO WARRANTY EXPRESSED OR IMPLIED! I may be wrong, have in the past and will be in the future!

VintageCarryall
Frequent Contributor
Posts 2249
06-05-09 04:46 PM - Post#1711789    

On a hunch; swapped out the EGR valve with a new GM part--------hesitation went away. Apparently; the return spring was weak and/or there was a slight internal leak in the valve.

I pulled #'s 1 & 3 sparkplugs; they are burning perfectly.

Pinging is still there but nothing like before--------and, the car runs well now
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


1983G20Van
Super Senior Member
Posts 3223
06-05-09 07:41 PM - Post#1711867    

  • VintageCarryall Said:
On a hunch; swapped out the EGR valve with a new GM part--------hesitation went away. Apparently; the return spring was weak and/or there was a slight internal leak in the valve.

I pulled #'s 1 & 3 sparkplugs; they are burning perfectly.

Pinging is still there but nothing like before--------and, the car runs well now



Actually the backpressure release valve/pin was probably clogged, which allowed the actual valve to open as soon as it recieved vacuum, rather than modulate the opening of the valve and the EGR flow.
1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals

Chevytech
Subject Matter Expert - Senior Member
Posts 3094
06-06-09 07:11 AM - Post#1712007    

  • Quote:
Actually the backpressure release valve/pin was probably clogged, which allowed the actual valve to open as soon as it recieved vacuum, rather than modulate the opening of the valve and the EGR flow.



Weak or broken EGR springs do happen, but not as often.

Here is an image that will help you understand what 1983G20Van is saying. There is more to the EGR valves then people realize.



Image source if image does not show;
http://shbox.com/1/EGR_valve.jpg

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

VintageCarryall
Frequent Contributor
Posts 2249
06-06-09 09:15 AM - Post#1712044    

In other words: I had to replace the EGR valve since there is no way to repair them.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


elkiebob
Forum Newbie
Posts 20
06-10-09 01:44 PM - Post#1714698    

I had a bad pinging problem and I was running regular unleaded. Switched to premium and after 2nd tankful, pinging stopped. It's that simple.
I didn't touch it, really.

VintageCarryall
Frequent Contributor
Posts 2249
06-13-09 04:54 AM - Post#1716222    

UPDATE:

The driveability of my 1989 Caprice is now quite decent; but, I am only averaging 10-12 MPG in mixed city/freeway driving.

Any ideas here? Remember the vehicle passed emissions with flying colors.

And yes, car still has a pinging problem but, much less since I corrected the EGR problem.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Chevytech
Subject Matter Expert - Senior Member
Posts 3094
06-13-09 04:53 PM - Post#1716532    

  • VintageCarryall Said:
UPDATE:

The driveability of my 1989 Caprice is now quite decent; but, I am only averaging 10-12 MPG in mixed city/freeway driving.

Any ideas here? Remember the vehicle passed emissions with flying colors.

And yes, car still has a pinging problem but, much less since I corrected the EGR problem.



If the engine pings, the knock sensor will detect the pinging, and the timing will be retarded in an attempt to stop the pinging. This will hurt performance and gas mileage.

The 305 TBI engines, which is what I believe would be in your Caprice, would have a compression ratio of 9.3 to 1, which higher then a 350 or other engines. Carbon buildup is more of a problem for the 305 because with ethanol in the fuel and a 9.3 to 1 compression ratio you are already pushing the limit toward pinging.

Carbon deposits not only raise the compression ratio farther, but the deposits can greatly affect the flow in and out of the engine.

As it has been mentioned, I strongly suggest you try a product like Sea Foam.

  • bowtie67 Said:
The engine is probably carboned up, try seafoaming the engine before replacing things, also the possiblity of some bad gas.



  • Twilightoptics Said:
Try the seafoam.

At very least pull the intake and clean the EGR passages thoroughly, and clean the passages in the head.



  • hoppycamaro Said:
…….. if the engine is in sound mechanical order then start by cleaning out carbon with whatever methed you like best.
jason



  • bowtie67 Said:
……………. Ways of removing carbon can vary, If the engine is severey carboned up you will have to use heavy duty products, Seafoam Engine treatment soaks into the carbon to soften and burn it out, I have used water, transmission fluid and even GM had a product to cleanout carbon. ……………... When excessive carbon is happening the pistons tops and chambers in the heads get carboned and this increases compression …………….. I have seen some cars so bad that the EGR was plugged solid, …………, the crossover passage plugged,……….



  • Scotts Auto Said:
……………. After finding the egr port plugged and cleaning it out, you developed off idle hesitation/stutter……………..

Cleaned without removing intake – may still have one bank plugged.



For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

VintageCarryall
Frequent Contributor
Posts 2249
06-13-09 06:36 PM - Post#1716594    

  • Chevytech Said:
  • VintageCarryall Said:
UPDATE:

The driveability of my 1989 Caprice is now quite decent; but, I am only averaging 10-12 MPG in mixed city/freeway driving.

Any ideas here? Remember the vehicle passed emissions with flying colors.

And yes, car still has a pinging problem but, much less since I corrected the EGR problem.



If the engine pings, the knock sensor will detect the pinging, and the timing will be retarded in an attempt to stop the pinging. This will hurt performance and gas mileage.

The 305 TBI engines, which is what I believe would be in your Caprice, would have a compression ratio of 9.3 to 1, which higher then a 350 or other engines. Carbon buildup is more of a problem for the 305 because with ethanol in the fuel and a 9.3 to 1 compression ratio you are already pushing the limit toward pinging.

Carbon deposits not only raise the compression ratio farther, but the deposits can greatly affect the flow in and out of the engine.

As it has been mentioned, I strongly suggest you try a product like Sea Foam.

  • bowtie67 Said:
The engine is probably carboned up, try seafoaming the engine before replacing things, also the possiblity of some bad gas.



  • Twilightoptics Said:
Try the seafoam.

At very least pull the intake and clean the EGR passages thoroughly, and clean the passages in the head.



  • hoppycamaro Said:
…….. if the engine is in sound mechanical order then start by cleaning out carbon with whatever methed you like best.
jason



  • bowtie67 Said:
……………. Ways of removing carbon can vary, If the engine is severey carboned up you will have to use heavy duty products, Seafoam Engine treatment soaks into the carbon to soften and burn it out, I have used water, transmission fluid and even GM had a product to cleanout carbon. ……………... When excessive carbon is happening the pistons tops and chambers in the heads get carboned and this increases compression …………….. I have seen some cars so bad that the EGR was plugged solid, …………, the crossover passage plugged,……….



  • Scotts Auto Said:
……………. After finding the egr port plugged and cleaning it out, you developed off idle hesitation/stutter……………..

Cleaned without removing intake – may still have one bank plugged.







And; let me guess (as you can see, driveability is not my strong suit------I am an alignment tech); the retarded timing may be causing the car to possibly run almost 'pig rich' since the catalyst seems to be running a tad warmer than comfort.

Once I hit 200 miles on this tank of gas, I am going to fill it up with premium and go from there.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Chevytech
Subject Matter Expert - Senior Member
Posts 3094
06-14-09 06:43 AM - Post#1716784    

  • VintageCarryall Said:


………..the retarded timing may be causing the car to possibly run almost 'pig rich' since the catalyst seems to be running a tad warmer than comfort.

Once I hit 200 miles on this tank of gas, I am going to fill it up with premium and go from there.




The engines that I have found with the most carbon deposits are 305 V8 caprice engines.

If you think it is running rich:

Make sure the thermostat is getting it to 195 degrees.

Test the coolant temperature sensor that the ECM uses. I can post specs for testing or you can do a search with "Chevytech" and "coolant temperature sensor" and you should find specs.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

VintageCarryall
Frequent Contributor
Posts 2249
06-16-09 04:55 PM - Post#1718309    

  • Chevytech Said:
  • VintageCarryall Said:


………..the retarded timing may be causing the car to possibly run almost 'pig rich' since the catalyst seems to be running a tad warmer than comfort.

Once I hit 200 miles on this tank of gas, I am going to fill it up with premium and go from there.




The engines that I have found with the most carbon deposits are 305 V8 caprice engines.

If you think it is running rich:

Make sure the thermostat is getting it to 195 degrees.

Test the coolant temperature sensor that the ECM uses. I can post specs for testing or you can do a search with "Chevytech" and "coolant temperature sensor" and you should find specs.





Guess what: on a hunch the driveability tech scanned my car again and the thermostat not only read 165F---------I took the housing off the intake and the innards of said 'stat' were missing.

Threw in the correct 195F piece; fired up the car and waited about 5-10 minutes for it to crawl up to ca. 190F. Looked at the spray pattern of the injectors and it seemed a bit 'sparser' so I am on the right track.

Side note: I rebuilt the fuel pressure regulator first which may have helped a tad.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


VintageCarryall
Frequent Contributor
Posts 2249
06-17-09 07:30 PM - Post#1719067    

My beast threw another 'Check Engine' light this morning; scanner told me a Code 45.

I noted that my O2 sensor was in 'open' mode; so I replaced it...........the car now runs great and the fuel gauge no longer drops like a Holley Double Pumper equipped vehicle.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Chevytech
Subject Matter Expert - Senior Member
Posts 3094
06-19-09 07:34 AM - Post#1719851    

Glad to hear you are making progress, and thanks for sharing what you have found.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

VintageCarryall
Frequent Contributor
Posts 2249
07-11-09 09:06 AM - Post#1732832    

Car runs well aside from still pinging; although it has been hot here lately (110F+). The fuel economy does suck, sorry to say. We are discussing maybe 12 MPG in admittedly surface street driving.
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


Chevytech
Subject Matter Expert - Senior Member
Posts 3094
07-19-09 10:29 AM - Post#1737891    

  • VintageCarryall Said:
Car runs well aside from still pinging; although it has been hot here lately (110F+). The fuel economy does suck, sorry to say. We are discussing maybe 12 MPG in admittedly surface street driving.


That 305 has a 9.3 to 1 compression ratio. WITHOUT THE CARBON BUILDUP FROM THE COLD THERMOSTAT THAT WAS IN IT.

If you are using an ethanol blend of regular unleaded fuel, in a hot climate, it is close to pushing the limit.

The 350 TBI engines have a 9.0 to 1 compression ratio.

Try putting some premium fuel in it and see if the pinging stops. If this stops the pinging, I suggest using Sea Foam down the TBI with the engine warm to try to clean out some carbon deposits.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.

VintageCarryall
Frequent Contributor
Posts 2249
07-21-09 07:06 PM - Post#1739582    

  • Chevytech Said:
  • VintageCarryall Said:
Car runs well aside from still pinging; although it has been hot here lately (110F+). The fuel economy does suck, sorry to say. We are discussing maybe 12 MPG in admittedly surface street driving.


That 305 has a 9.3 to 1 compression ratio. WITHOUT THE CARBON BUILDUP FROM THE COLD THERMOSTAT THAT WAS IN IT.

If you are using an ethanol blend of regular unleaded fuel, in a hot climate, it is close to pushing the limit.

The 350 TBI engines have a 9.0 to 1 compression ratio.

Try putting some premium fuel in it and see if the pinging stops. If this stops the pinging, I suggest using Sea Foam down the TBI with the engine warm to try to clean out some carbon deposits.




I put some premium into the car and the pinging is about half of what it was before.

And; 115F does qualify as a hot climate
1994 Dodge Caravan SWB 3.3L V6
1962 Studebaker Lark 4 door 350 Chevy/TH350


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