FuelforWar

Got it fixed and replaced. No luck. My truck still stumbled on me and started to stutter. Started poking around some more and noticed something else, when I turn off the truck I hear a hiss from the charcoal canister. I know this is part of the evap system. Any chance this component could cause an interference?

FuelforWar

Well tried somemore stuff this weekend. Still no luck. Did a compression test. All my cylinders are between 174 and 180. I seafoamed the intake plenum and replaced all the vaccum lines in case I missed something. Stutters still there. Ugh... this is getting frustrating. So heres a recap of whats been checked or replaced...

Tps
Vafm
Fuel filter
Fuel pump + sock
Grounds checked
Fire order
Timing
Full tune up
02 sensor
Vaccum lines
Seafoamed + injector cleaner in tank (burned full tank)
Seafoamed intake plenum
Pulled codes (none)
Reset computer

?????.....

Gevo

Is it still happrning randomly? Is it more or less frequent? Try to pay close attention when it happens and see if you can find some common situations that it reaccures in.

Also a thought.. although unlikely.. test the distributor pi kup coils. I dont know if its yhe kind of device that can work most times but fail intermittently. Worth a test though. If they are giving imlproper info to ecu that could be causing spark timing issues since it all relates to the camshaft position.

FuelforWar

Its still happening unfortunally. Pretty much im going through every piece of that engine compartment til theres nothing left to look at. I cant make the problem reoccur but drom what I can tell it happens most the time right after I shift into second gear with moderate gas being applied. It also seems to do it alot while just cruising in 4th

Gamefreakgc

I've been there... just keep checking sensors and components until you find the culprit.

Here's a few to check out if you haven't already (see this link for basic locations: http://personal.utulsa.edu/~nathan-b...electron.pdf):

1. Circuit Opening Relay (COR, located along the passenger side in the cab above the ECU, I believe): http://personal.utulsa.edu/~nathan-b...96circuito.pdf

2. Engine Coolant Temperature sensor (located on water bypass on the backside of the engine): http://personal.utulsa.edu/~nathan-b...98engineco.pdf

3. Cold Start Injector Switch (next to ECT, probably not your issue but you'll be back there anyway): http://personal.utulsa.edu/~nathan-b...ne/97colds.pdf

4. Cap and rotor - Take off the cap of your distributor and check to make sure the contact points are shiny with no rust or corrosion. Do the same for the rotor. If in doubt, replace since it's a regular maintenance items on these engines.

The ECT check and CSIS are straight forward, disconnect connector and use multimeter to check resistance. Easiest done a a cold engine since you won't have to guess what temperature the coolant is.

The circuit opening relay is more of a confirmation than a issue. This is what supplies voltage to the fuel pump and other components. If it has issues, then replace. The check is rather complicated though, since you have to run a 12 volt current over it to check correctly. Or just turn on the ignition to make sure it "clicks".

FuelforWar

Thanks for the info. The cap and rotor are new and I replaced my ECT 6 months ago when I accidently snapped off the post. The rest I will check out and confirm if checks out.

Gamefreakgc

Mine did that too... the CSIS probably is corroded through as well but doubt that's your issue. A broken CSIS would only make it start poorly in sub-freezing weather.

FuelforWar

Multiple-Cylinder Leaks
Found this nice bit of info. Gonna look into it.


"Multiple-cylinder leaks tend to happen after a botched manifold installation. It could happen because of improper manifold torquing, a bad or damaged gasket, improper gasket installation or warped mating surfaces on the cylinder head or manifold. If you've got multiple vacuum leas, your engine ingests far more air than it should. This causes a loss of power, stumbling and hesitation on acceleration, and poor fuel economy.

FuelforWar

PROBLEM RESOLVED!

Turns out I had a huge leak between my intake plenum and the intake manifold. 2 bolts on the drivers side were loose and I found seafoam residue all over the gasket and flange mating surfaces. I went ahead and cleaned the entire plenum out, painted it, same with the throttle body, and jetted all the hard vaccuum lines out with carb cleaner. Put it all back together and my truck is amazingly quieter. I never realized it was leaking that bad and for that long. I hope this info is of help to someone and thanks to everyone who put in there two cents and tried tohelp me. it was greatly appreciated.

Gevo

Glad to hear! Im working on solving my own bad idle when cold after engine rebuild... lol

Gamefreakgc

Glad you got it figured out! That was a hard one...

Too bad that's not my issue though... I already ensured mine doesn't leak.

FuelforWar

Did you check the manifold as well?

Gamefreakgc

I haven't gone so far to check the seal between the manifold and the cylinder heads because for how infrequent and minor the symptoms are for me. No performance issues and good gas mileage, so I can't justify going that deep for a problem that may or may not be there. But if I ever do, I'm gonna check that one for sure.

FuelforWar

Yea I get that. Mine was too horrible to let go. Let me know if you find your problem. Im curious what it is.

FuelforWar

Oh on a side note I took my truck to seattle for the first time since the repair. Its like night and day the difference. I never had to leave 5th gear. The truck accelerates smooth and can easily hold the speed limit. Before I had to really push it just to keep the speed limit and I was constantly having to throw it into 4th on any slight incline just to sustain the speed I was going. I also tracked my gas mileage today. Went from 12 mpg to 15.72. Soooo happy

Gamefreakgc

Dang, you had a massive leak then! That's awful... 3.0's should hold 5th with little issues. Glad you got it fixed, probably feels like a whole new engine!

FuelforWar

My driving style will change dramatically lol

ChzSoda

Posting to subscribe and chime in with extremely similar symptoms. I'll move 'checking for plenum leaks' to the top of the list.

FuelforWar

Been a while since I posted but I just wanted to state my problem returned a few weeks later. Got tired of trying to hunt down the issue so I bought a commuter to take the stress away. Vehicle is parked atm and I plan on dropping the 5vze in it soon. Hope the rest of you were able to figure it out. I miss taking my truck out. Been stuck to wheel in on my property.

Barwench

Not sure how extensively any of you who have this problem have checked your vafm. I got desperate enough to open mine up. What I found is the wheel appears to have been slipping teeth, if that makes sense. The lock has left scratch marks on it, don't know if it's metal fatigue or what. It makes sense to me, since the truck would run like crap, but improve after a day or so, then run a little worse, then improve from that, etc. I assume it has been slipping one tooth at a time. Just curious if anyone else has seen this.