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Username Post: Update on stumbling/bucking 98 5.0L K1500 Vortec        (Topic#187546)
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-18-08 04:48 AM - Post#1414014    

I'm posting this a little sooner than I wanted to but Trailwart asked about it.

Truck started out with a bucking issue and also had a starting stalling issue and threw a camshaft position sensor code. I put in a new camshaft position sensor but still had the bucking issue and couldn’t get rid of the code. Noticed that when I moved the large wiring harness on top of the intake the engine would stumble. Found the middle wire from the weather pack plug going into the harness was rubbing on the transmission which caused it to fray. Put in a new plug and replaced the following sensors:

Camshaft position sensor,
Crankshaft position sensor.
Throttle position sensor.
Coolant temperature sensor (Tried two new sensors)
O2 sensor, the one in front of the cat not the one behind the cat.
PCV valve.

I took the EGR valve off and activated the solenoid with 12 volts from the battery and felt it change position. I took the IAC valve of the throttle body and checked it for carbon, didn’t see any issues there.

Got rid of the codes but still had the bucking issue.

Then I rebuilt most of the fuel system:

New gas tank
New Bosch fuel pump - 56 psi
Took it out
Put in a new AC Delco fuel pump - 56 psi
Both fuel lines from the tank to where they terminate at the fuel filter.
New fuel filter.
Blew out the fuel lines to the upper intake with air to see if clogged.
New fuel pressure regulator.
New fuel pump relay.

Still had the bucking issue.

Then I rebuilt the ignition system with AC Delco parts except the coil.
New platinum plugs
New Wires, distributor cap and rotor
New coil from Advance Auto.



Still had the bucking issue. When I took it for a ride it started bucking and the check engine light came on and threw 7 codes which were for mostly the new sensors.

OBD2 DTC (Codes

P0102
MAF or VAF
Circuit Low Input

P0118
Engine Coolant Temp
Circuit High Input

P0122
TPS/Pedal Position
Sensor A
Circuit Low Input

P0339
Crankshaft Position Sensor A
CKT Intermittent

P0340
Camshaft Position Sensor A – Bank 1 Circuit Malfunction

P0405
EGR Flow
Sensor A
Circuit Low Input

DTC Pending (Codes)

P0147
O2 Sensor Heater
Circuit Malfuntion
(Bank 1 Sensor 3)

P0339
Crankshaft Position Sensor A
CKT Intermittent

Now I'm about as far as I can go with this thing so I found a good mechanic who agreed to drive the truck around with a Tech 2 scanner plugged into it while driving it. Well it turns out that the new crankshaft position sensor was bad. While he was driving it would start stumbling and bucking, he looked at the Tech 2 and it said the engine was cranking 7,000 rpm which we think was causing the ECM to tell the engine to shut down at the same time the ECM was trying to compensate which caused all of the other sensor codes to go haywire. He put in a new crankshaft position sensor and he agreed to drive it around using it for pickups deliveries etc. for three days. Stumbling and bucking issue is gone and I drove it around last night without any issues.

So all in all the starting and stalling issue got cleared up with the new fuel pump. The stumbling and bucking issue almost drove me crazy because not only did I have a brand new crank position senor that was bad I had that frayed wire coming from the camshaft position sensor that was working at times then other times it wasn't giving me intermittant codes.

In the middle of all this I had the lower intake leak so I had to take the intakes off and fix all that to boot so while I was in there I replaced the fuel pressure regulator and cleaned all of the injectors.

Aside from driving me crazy for two months it may turn out alright because now I've basically got a new fuel and ignition system so it should run for a good long time without any issues I hope

I'm driving off Cape this afternon and back this weekend so we'll see how it does.

2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


 
someotherguy 
Moderator
Posts: 25538
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
04-18-08 05:03 AM - Post#1414026    
    In response to TwentyBucks

Wow Les; this one has put you through the wringer. I have to ask, was the new crank position sensor a GM part from the dealer, or aftermarket from the parts house? I ask because I think the bogus parts situation is bad and just going to get worse.

I know a lot of you Vortec guys really love your trucks but stuff like this is part of why I try to avoid them. It's a great engine but if you ask me they made it just a wee bit too complex in the control systems.

I've got a little dread reserved for when I delve into the slight drivability problems my '98 Vortec 7.4 has.

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


 
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-18-08 05:10 AM - Post#1414031    
    In response to someotherguy

It was an AutoZone sensor. The mechanic told me that I might be able to put in a labor claim for the bad sensor. He also said that his shop is seeing this more and more - brand new sensors which are junk. The trouble with that is you get guys who work on their trucks, put in new sensors and still have problems which can really drive you nuts.

I'll agree with you about the Vortec - it is an extremly touchy motor. If everything isn't spot on you'll have problems.
2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


Edited by TwentyBucks on 04-18-08 05:12 AM. Reason for edit: No reason given.

 
someotherguy 
Moderator
Posts: 25538
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
04-18-08 05:13 AM - Post#1414039    
    In response to TwentyBucks

Even buying OEM parts directly from the dealer doesn't make you immune to stuff like this, but I think there's less of a chance of it.

Of course, I should practice what I preach - the O2 sensor I bought for my '94 the other day came from the parts house; Bosch brand. Seems to be working okay but I had to really fight it in as the harness on it was about .5" too short to reach.

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


 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
04-18-08 05:19 AM - Post#1414044    
    In response to TwentyBucks

  • Quote:
new crankshaft position sensor was bad.



GEEEEEESH

We would like to suggest taking rigs to a dealer or competent mechanic with a Tech II or similar, but as far as I'm concerned I hate to suggest it because of the expense-----when most of the time, it can fixed without it.

I guess I got burned early on----here on CT, with members telling horror stories of going to dealers and all they got was a code reading and charged $100 of course not all are like that.

I've been very fortunate from the beginning to have a life long buddy that has a shop and TECH II. Mine has never been on there for diagnostic purposes except to try different things where he and I wanted to learn what was going on, and nearly always we were out driving it-----taking snapshots. But if an issue ever appears, he's always there for me and I try to return in kind.

Boy, let's hope this cures yours, it should be "good to go" for a few hundred K miles.

Was the sensor a generic, or GM?

 
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-18-08 05:23 AM - Post#1414048    
    In response to someotherguy

I think all of these parts now are made in China, Brazil etc. but I would trust the OEM stuff more than the chain store stuff.

I'll never forget I interviewed for a manufacturing engineer position at Texas Instruments about 15 years ago. TI at the time made huge amounts of automotive sensors for the industry. The guy tells me he's got this machine out on the floor that is automatically assembling and spitting out 25 sensors per minute, the only trouble was about 20 percent of the senosrs coming off the machine were bad! They had people checking each sensor but some do get missed and wind up in the store so that's what can happen.
2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


 
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-18-08 05:28 AM - Post#1414053    
    In response to CDAUSA

I know going to the dealer these days can be hit or miss and the labor rate is around $90 an hour now.

I'm lucky I found this guy willing to ride around with a Tech 2 plugged in. Poor guy almost got stuck at the middle school with his daughter on Monday.
2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
04-18-08 05:37 AM - Post#1414061    
    In response to TwentyBucks

Sad part is these rigs and complete engines are going to the crusher, hundreds a day. With them are going some perfectly good sensors and hardware---things that would keep ours running fine for decades.

I bought a double handful of sensors and stuff out of a wrecking yard the other day, all headed to the crusher, for $15. I told the guy to let me know before anything like that happens again------I'll finish loading the back of my pickup up with stuff

 
trailwart 
Contributor
Posts: 256

Reg: 04-17-08
04-18-08 08:35 AM - Post#1414207    
    In response to CDAUSA

thanks for the follow up. i think i have to find someone with a tech 2 to diagnose mine. i have the fuel injecter/poppits i need to clean and if that doesnt work i will have no choice but to pay someone.

 
Boog 
Super Senior Member
Posts: 3530
Boog
Loc: Central Arkansas
Reg: 04-28-02
04-18-08 09:46 AM - Post#1414272    
    In response to trailwart

Being one who has always done all his repairs I am hesitant to suggest anyone take their rig to the dealer but in some cases it can be cheaper than going by what this guy and that guy said "could" be the problem. This is of course based on the competence of the dealer's mech behind the Tech 2 scanner.
Boog
69 Chevy step
06 GMC ccsb Z71
00 GMC excab Z71
All GM...'nuff said!
JR Nation


 
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-18-08 10:48 AM - Post#1414312    
    In response to Boog

I guess what it really comes down to is fixing all of the things that you know are wrong - in my case I knew I had low fuel pressure; 51 psi so the tank and fuel pump was a no brainer. Some things you can guess at and then there comes the point where you really need to bring it somewhere. The tricky part is knowing when to do that and who is competent enough to diagnose what the issue is.
2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


 
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-21-08 07:11 AM - Post#1416335    
    In response to trailwart

Well I drove it around all weekend, put 150 miles on it without even a sniff of any stumbling, bucking or any other driveability issues So I guess the new crankshaft position sensor was the last problem - which I had many, solved.

Thanks to CDAUSA and Someotherguy for helping me and offering advice through the last couple of months while I wrestled with this thing.
2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


Edited by TwentyBucks on 04-21-08 07:14 AM. Reason for edit: No reason given.

 
trailwart 
Contributor
Posts: 256

Reg: 04-17-08
04-22-08 10:34 PM - Post#1417954    
    In response to TwentyBucks

following your post, and finding many like this 1, had me take it to an old friend that worked at the gm proving grounds. he happened to have a tech 2, could not find anything out of the ordinary except it was pulling up alot of misfires on te screen. he said he never recomends these gas tanks to be ran below half a tank but he told me instead of taking my upper plenum off, to let it run down on/near empty. then add 4 bottles of stp injector cleaner in the tank, stop at the gas station and add about 4 gallons of gas and hity the highway. after about 50-60 miles the stumbin was gone. each bottle of the cleaner treats 17 gallons, so i was running a high concentrate, he figured it was the poppits. told me if/when the problem comes back to get the upgraded spider. as a preventative measure to run a bottle of cleaner every other tank.

 
TwentyBucks 
Contributor
Posts: 283

Loc: Cape Cod, MA
Reg: 11-06-07
04-23-08 04:39 AM - Post#1418033    
    In response to trailwart

If that is what it took to get it right then you had an easy fix. I have heard many times as well to try and always keep at least a half of tank of gas at all times. I bought a brand new 03 Suburban and the tank has never had less than 1/2 tank in it.
2010 Cadillac CTS
2003 Suburban 4X4
98 K1500 5.0L
2002 Honda Civic, commuter car


 
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