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Username Post: 92 Chevy Silverado Problems        (Topic#210009)
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-19-09 07:43 AM - Post#1633531    

My 92 Silverado starts fine, but idles a little rough, has a lack of power and knocks/pings when accelerating. I have changed plugs/wires. Does anyone have any idea what the problem is?

 
someotherguy 
Moderator
Posts: 25155
someotherguy
Age: 43
Loc: Texas
Reg: 08-01-03
02-19-09 09:09 AM - Post#1633592    
    In response to KEVRO

Hi and welcome to the forum;

Likely suspects - you could have a base timing problem, EGR valve problem, and possibly bad/disconnected knock sensor. Before throwing parts at it though (especially the EGR since it's best to get the "real" one, and that's $70+) let's get some more info and we can try to help you troubleshoot it first.

What engine do you have, and how many miles on the truck? Is this a new problem, or roughly how long has it been present? Any work done before this happened?

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-19-09 09:50 AM - Post#1633623    
    In response to someotherguy

The engine is a 350 5.7L with 85,000 miles. Truck has this problem for a couple of months off and on. It would run great for a week or two and then start to act up. The knocking/pinging started this week, so I changed the plugs and wires.

I appreciate your help Richard.

Thanks,
Kevin

 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-19-09 09:55 AM - Post#1633624    
    In response to KEVRO

To add a little history - I only drive 1 mile to and from work a day. Truck has been a jewel, never had to do anything but replace starter and water pump.

 
The_Hunter 
Contributor
Posts: 983
The_Hunter
Loc: Manitoba, Canada
Reg: 02-14-05
02-19-09 10:03 AM - Post#1633634    
    In response to KEVRO

With the truck idling squeeze in the egr valve, located behind the throttle body on passengers side. Does the idle get worse? After a few squeezes does the idle improve? A piece of carbon may have gotten lodged the the pintle, maybe you could free it up this way.

What condition is your cap and rotor in?
86 C10 Short Box

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


 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-19-09 11:49 AM - Post#1633688    
    In response to The_Hunter

With the truck idling squeeze in the egr valve, located behind the throttle body on passengers side. Does the idle get worse? After a few squeezes does the idle improve? A piece of carbon may have gotten lodged the the pintle, maybe you could free it up this way.

What condition is your cap and rotor in?

Being a non-mechanic, where do I need to squeeze in on the egr valve?

The cap and rotor look fine. They are factory.

Thanks for your help.

 
The_Hunter 
Contributor
Posts: 983
The_Hunter
Loc: Manitoba, Canada
Reg: 02-14-05
02-19-09 02:40 PM - Post#1633802    
    In response to KEVRO

On the bottom side of the EGR valve, that's facing the throttle body side you will see 3 or 4 large openings in the metal casing. inside you will see a metal diaphram, that is what you want to squeeze. Use 2 fingers, one of each side of the "shaft" connected to the intake manifold, and press down evenly.

Beware that all the components will be warm in this area, don't burn yourself!

For reference, this is what an EGR valve looks like:

86 C10 Short Box

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


 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-20-09 06:10 AM - Post#1634284    
    In response to The_Hunter

I removed EGR valve and cleaned with paint thinner. This removed a bunch of carbon buildup, althouth the rough idling and the knocking/pinging is still there.

Have any other ideas?



 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-20-09 06:32 AM - Post#1634303    
    In response to someotherguy

Should I check the timing? or replace distributor cap? I bought a new fuel filter, but have not installed yet. Also, I am driving truck daily. Will this harm the engine or is it too far gone to even worry?

Thanks for any further suggestions

 
someotherguy 
Moderator
Posts: 25155
someotherguy
Age: 43
Loc: Texas
Reg: 08-01-03
02-20-09 11:38 AM - Post#1634536    
    In response to KEVRO

If it's pinging a bunch, you're doing damage to the engine. That beats on the pistons, bearings, valves...it's not good.

If you know someone with a vacuum tester (Mityvac or similar) you can hook a line to it and try to pull vacuum on the EGR. With the engine off, you should be able to pull around 10 inches or so of vacuum without it bleeding off immediately. If it can't do this, the EGR is probably bad. (To be thorough, there are EGR valves that work the exact opposite of this, but yours being a '92 350 in a light truck, is the negative pressure style.)

If the EGR can hold vacuum, then we've got other troubleshooting to do. (EGR solenoid, vacuum supply to it, etc.)

Yes, check the timing. With the engine warmed up, tan/black wire disconnected (on your '92 it should be behind or near the black plastic convenience center cover on the passenger side of the firewall) you should see 0 degrees or something very close to it. A couple degrees advanced is OK but 0 is the spec.

Finally a bad knock sensor can contribute to pinging but for it to be pinging that much, it pretty much can't be JUST the knock sensor; other factors are involved.

Finally, could be a nasty amount of carbon buildup in your combustion chambers since it sounds like you take a LOT of very short trips.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
SuperSport 
Super Senior Member
Posts: 6501

Reg: 07-03-01
02-20-09 12:09 PM - Post#1634561    
    In response to someotherguy

Could be fuel pressure.


 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-20-09 12:15 PM - Post#1634565    
    In response to SuperSport

How do u check fuel pressure?


 
edetweiler 
Forum Newbie
Posts: 8

Age: 49
Loc: Kent, Ohio
Reg: 02-11-09
02-20-09 02:01 PM - Post#1634630    
    In response to KEVRO

I'm not too sure about any EGR valves' compentency after recently removing my intake manifold and finding both ports {which lead to the EGR Valve} completely clogged with soot, had to just about chisel them out. I think I replaced the EGR valve about 120,000 miles or more before on a whim, while throwing parts at a different problem. This truck currently has 315,000 miles on it and I have never had any problems that led back to the EGR Valve. Just my 2 cents on this subject. On the problem at hand, I suggest maybe a new Dist. Cap and rotor. I personally replace these two items with every new set of plugs that I install, no questions. Also look for vaccum leaks at all vac. lines. U might even pull the ECM from distributor and run it down to NAPA for a free test.
1993 4WD 5.7 Suburban 2500
1996 2.2 Cavalier
2001 ZX2 Escort


 
someotherguy 
Moderator
Posts: 25155
someotherguy
Age: 43
Loc: Texas
Reg: 08-01-03
02-20-09 02:23 PM - Post#1634643    
    In response to edetweiler

An EGR valve cools the combustion chamber by introducing exhaust gas back into the intake; without it you are more prone to pinging.

The wrong one, or one that opens too easily because it's gone bad, can cause very poor idle/part throttle quality, even stalling off idle.

I've experienced both of these exact symptoms, both on TBI 5.7's in trucks like ours.

On one truck, a '94 Suburban, I had a slight ping for a while that I ignored until it suddenly got VERY bad - retarding the timing a few degrees and running premium fuel as a temporary measure wouldn't shut it up. I tested the EGR valve and it was failing to open. Replaced it, still had some ping - turned out the knock sensor was bad, too. (By the way it's not as simple as you might think to properly test one.) Obviously one or the other was bad, causing the slight ping, then the other went and I had the "perfect storm" for pinging. Once I replaced the knock sensor and set the timing back to spec (actually I left it at 4 degrees advanced for a slight boost) the engine was happy again.

On another truck, a '92 pickup, I replaced a blown engine with a good used one but had the wrong (or possibly just bad) EGR valve. The engine had a severe lope at idle and part throttle like it had an aggressive cam in it, though it was bone stock. Sometimes it would even stall when transitioning from idle to part throttle if I didn't give it enough pedal. Replacing it with a new and correct EGR valve solved the problem 100%.

I'm happy you've gone 300K+ plus without an apparent issue due directly to the EGR but my advice is to never write off the EGR as a potential source of trouble, nor should you underestimate its importance in the overall engine control system.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
jbknight311 
Frequent Contributor
Posts: 1011
jbknight311
Loc: Fort Worth, TX
Reg: 11-27-06
02-20-09 02:49 PM - Post#1634659    
    In response to someotherguy

Richard,
Thanks, nice writeup. I think I will pick up a gasket and check mine soon. Been 226k miles and ain't done it yet. Now if I could just get that dern ICM to work like its suppose too.

I also like Steve's thought of putting never seize on the gasket so it can be reused in the future.

You so right on never suspecting something can be the problem. Bit me more then once. We have read EGR problems a couple times a quarter it seems. It also seems like they slowed down some lately.

KEVRO - to check your fuel pressure you usually splice a guage into the fuel line. Tee off it to hook up the gauge and clamps on the rubber to hold it in. Another thing you can do on your TBI is put a container under the fuel filter, remove the inlet side and turn the key on to start the pump. It should give a pretty good stream into the bucket. Caution, this is gas so no smoking and make sure you have it go into something and not spray around. The truck shouldn't start, you are just checking the fuel pump. Now, that don't check the pressure regulator which is part of the throttle body. That is another test.

Also, when you removed the EGR valve, you cleaned the ports on it, but there could be a lot of clogged under it in the passages. Also, there is a diaphram inside the valve that could be leaking and not letting it work. So, the idea of the vacuum test of it is in order.

Since you only drive it about a mile at a time and low miles and only acts up every 2 weeks or so, have you changed the fuel filter, checked for water in the tank and checked the pattern of the spray injectors? They should be nice cone shaped spray.

The idle control valve could also be an issue, but what throws me is it seems to happen the same frequency as most people fill their gas tanks with yours.
Do you ever run it on a long run and get the speed up? Just may be needing a good decarboning. Blow it out as we use to do to ma's old Catalina. If you never let the engine get warm then you will have water in spots it ain't suppose to be, like inside the engine and exhaust. You will also have carbon buildup around the valves and in the heads. If it never heats up then it will always be running rich. So, the EGR valve is a good place to look as this would go with the carbon buildup.

I wonder what Seafoam would do in your engine? Might be a good way to go if you have a place to make some smoke for half an hour.


Have a nice weekend ya'll
Jeff
98 C1500 Silverado extended cab 5.7 auto 2wd Fort Worth, TX.


 
someotherguy 
Moderator
Posts: 25155
someotherguy
Age: 43
Loc: Texas
Reg: 08-01-03
02-20-09 06:29 PM - Post#1634839    
    In response to jbknight311

Hey Jeff, the bad part about yours being the '98 though is that it's not a vacuum-operated EGR. So you can't just throw a vacuum tester on it to see what's up.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
mrtube 
Senior Member
Posts: 246
mrtube
Loc: New jersey
Reg: 08-12-03
02-20-09 09:40 PM - Post#1634972    
    In response to someotherguy

just my two cents but, as far as i recall an EGR valve should never open during acceleration, only during cruising due to mixture being extreamly lean. then it is needed to cool the combustion. typically a ping while crusing and not during accleration would suggest clogged EGR, a wrong one or one opening too soon causes hesitation or even stalling.atleast that was how the ones in the 80s worked. i had an 87 grandprix with a 305 that was babied and driven short distances for 170K and it pinged so bad on sunoco 94 it was horrible, even with timing retarded 5-6 degrees. everyting worked on it perfectly, but the amount of carbon that had built up from the short trips and the fact it was never run past 2500rpm for all those years. if you set the base timing to 0 on it and tried to run 87, it sounded like a diesel. tho, i drove it for 5 years, with it pinging bad and somehow it never died.

recently my 92 c2500 with 350 and 220K miles was pinging sometimes. barely but youd catch a hint of it from time to time, ever since i put new injectors in it, it totally went away tho? same deal as low fuel pressure i spose

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 2922

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
02-21-09 01:09 PM - Post#1635295    
    In response to KEVRO

  • SuperSport Said:
Could be fuel pressure.


I agree

  • KEVRO Said:
How do u check fuel pressure?




Here is some info about fuel pressure testing I saved from a previous reply I made to a similar post. Hope the links still work.

C/K truck TBI systems do not have a fuel pressure test port, but the pressure must be tested with the engine running.

The fuel pressure is tested by using fittings to “T” in a pressure gauge. I like to T in the pressure gauge where the fuel filter is located. If the pressure is good, both the pump and regulator are ok. If the pressure is low it could be the pump or the regulator. If the test is done with a method that allows the fuel filter to be in place, a dirty filter can also cause low pressure. The regulator is inside the TBI unit. Stopping the flow in the return line momentarily will test to see if a low pressure problem is caused by the regulator. A bad regulator can let the fuel return to the tank instead of maintaining the correct pressure. If pinching off the return line, using care not to damage the return line hose, makes a low pressure reading surge above the specification pressure, then the regulator is the problem.

The TBI fuel pressure specification for small block Chevy’s is 9 – 13 PSI with the truck running.

Here are some web sites showing fuel pressure test equipment. The first tool gets installed where the fuel filter goes. Most people use the tool in the third site next to the TBI unit.

I you already have a pressure gauge like shown in the second web site below, all you need is the tool shown on the first web site. If not, the third would get the pressure tested for the least money.

http://www.sjdiscounttools.com/ta37650.html

http://www.actron.com/product_detail.php?pid=16174

http://www.actron.com/product_detail.php?pid=16175

http://www.cfm-tech.com/catalog/fuel_-_cfm-te ch_fu...

Another addition to the list:
http://www.tradervar.com/cgi-bin/store/agora.cgi?c...


  • Quote:
just my two cents but, as far as i recall an EGR valve should never open during acceleration, only during cruising due to mixture being extreamly lean.

Not true
TBI 1500 series trucks have No EGR operation at idle, but as soon same the throttle is opened the EGR can affect engine performance. There is EGR operation during acceleration.
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.


 
mrtube 
Senior Member
Posts: 246
mrtube
Loc: New jersey
Reg: 08-12-03
02-21-09 07:31 PM - Post#1635573    
    In response to Chevytech

fair enough.. by the way in a case like i had. with the huge buildup of carbon is there any way to get rid of it reliably without pulling the heads? a few told me GM had recommended using marvel mystory oil down the carb before they made "top engine cleaner" i tried it, it smoked like unbeleivable, but never improved anyting. probably clogged the cat in the end.



 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-23-09 08:25 AM - Post#1636513    
    In response to someotherguy

Richard - I replaced dist. cap/rotor and fuel filter over the weekend. I also squeezed on EGR valve while running and the engine shut down. I started it back and repeated, the engine kept running, but seemed to surge. I haven't got anyone to do a vacuum test yet, or do a diagnostic on it. Do you think EGR valve is still a problem?

Thanks for all the help.

 
someotherguy 
Moderator
Posts: 25155
someotherguy
Age: 43
Loc: Texas
Reg: 08-01-03
02-23-09 09:42 AM - Post#1636565    
    In response to KEVRO

What you've proven by squeezing the valve is that the passage for the EGR isn't completely clogged. You still need to pull vacuum on it to see if the ECM is capable of opening the valve (in other words if the EGR diaphragm is good.) While you have the vacuum tester you can also see if the EGR solenoid is good by hooking it to the output side of the solenoid (where the line to the EGR connects) and seeing if it pulls vacuum when you apply throttle.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
02-27-09 12:29 PM - Post#1639807    
    In response to someotherguy

I haven't done the vacuum test yet. A problem I failed to list is that the oil pressure gauge is maxed. I am not sure if it is a faulty gauge or something causing this extremely high pressure.

Any thoughts, if this is related to my other problems, or is it just an isolated problem?

Thank You

 
KEVRO 
Forum Newbie
Posts: 22

Loc: Tennessee
Reg: 02-19-09
03-04-09 10:46 AM - Post#1643620    
    In response to KEVRO

Had a vacuum test done, everything EGR valve checked o.k. My problem is low compression on 5 and 6. Will have to a head job.

Thanks to all for helping with my problem.

 
lilmikey042 
Lurker
Posts: 3

Reg: 03-01-09
03-14-09 03:19 PM - Post#1651497    
    In response to someotherguy

Hello,
I've got a '92 4.3L TBI motor with the same problem....would it be the same as the V8 TBI motor as far as the problem testing n fixin goes???

thanks lilmikey042

 
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