'94 Sonoma Running rough from 800-2800 RPMs HELP!

[06camarodude]

So I've noticed this problem for a couple of weeks now. I was driving my 94 Sonoma extended cab, Vortec 4.3 V6 Z VIN code, and it runs fine after a cold start, but starts bogging, chugging, and missing very badly after the engine warms up a bit. If I pull over, shut it off, and restart it, it will run fine for a couple of minutes, then it starts running badly again. Another thing I've noticed is that while it's running badly, if I floor the accelerator and get the RPM's up past about 3000 RPMs, it runs fine from 3000 RPMs to redline, but between idle and 3K, it runs like crap. It won't accelerate unless it's at full throttle. It's got an exhaust leak, I think it's the donut gasket at the manifolds. K&N Air Filter was put in, the drop in, not the FIPK. Replacing the wires tomorrow, checked the air cleaner, it's clean. Other than what I mentioned so far, I'm completely lost. Any help is appreciated. I did try a search, but no results matched the problem I'm having. Please help me!

[MT-2500]

Originally Posted by 06camarodude

So I've noticed this problem for a couple of weeks now. I was driving my 94 Sonoma extended cab, Vortec 4.3 V6 Z VIN code, and it runs fine after a cold start, but starts bogging, chugging, and missing very badly after the engine warms up a bit. If I pull over, shut it off, and restart it, it will run fine for a couple of minutes, then it starts running badly again. Another thing I've noticed is that while it's running badly, if I floor the accelerator and get the RPM's up past about 3000 RPMs, it runs fine from 3000 RPMs to redline, but between idle and 3K, it runs like crap. It won't accelerate unless it's at full throttle. It's got an exhaust leak, I think it's the donut gasket at the manifolds. K&N Air Filter was put in, the drop in, not the FIPK. Replacing the wires tomorrow, checked the air cleaner, it's clean. Other than what I mentioned so far, I'm completely lost. Any help is appreciated. I did try a search, but no results matched the problem I'm having. Please help me!

How is the basic tune up end?
Good plugs and what kind and filters and fuel pressure?
Ign base timing?
Any check egine lights?
Any stored codes?

[06camarodude]

Originally Posted by MT-2500

How is the basic tune up end?
Good plugs and what kind and filters and fuel pressure?
Ign base timing?
Any check egine lights?
Any stored codes?

No stored codes, K&N air filter, just replaced the fuel filter, cap and rotor are new, replaced the plug wires, plugs were replaced with ACDelco's right before I picked up the truck. It has an exhaust leak, I bought the new flange gasket, but I need to find out which side is bad. There are no stored codes, and the check engine light is not on. I ran it on a MACTools OBDI/OBDII scanner, and it's not showing any codes or anything. I went out to check the air filter, and the sensor that plugs into the air intake hose was out, and the plastic line that runs to the valve cover was also out, I don't know if that had anything to do with it, but I put them both in their proper locations, and it didn't do anything. I think it may be the fuel pump, but I don't know how to check that, and I have to work until midnight, so I'll be checking that out tomorrow. Any other suggestions? Oh yeah, I don't have any way of checking the ignition timing, but everything except the coil and plugs have been replaced so far, I don't know what to do. I got a $200 check this week, and I'm down to $20, everything else has gone into my truck.

[MT-2500]

I would get the exhaust leak fixed first it may be a no 1 problem.
Get the base time set.
You may be able to rent a fuel pressure gauge and or a timing light to check timing and fuel pressure from auto parts place.
And check that fuel filter.

[06camarodude]

Originally Posted by MT-2500

I would get the exhaust leak fixed first it may be a no 1 problem.
Get the base time set.
You may be able to rent a fuel pressure gauge and or a timing light to check timing and fuel pressure from auto parts place.
And check that fuel filter.

I was planning on checking the fuel pressure as soon as I can find a place to rent a guage, I don't know how to set the base ign. timing, so I might just hold off. . . Wouldn't the problem be evident at startup if it was a timing problem though? I have a couple of other concerns I'm going to address, like a loose wire for the remote starter, the positive power wire is VERY loose on the battery terminal, whoever hooked it up didn't snug it down properly, so I'm going to try and fix that, it ran fine up until that problem occured. The exhaust leak is probably going to be fixed on Tuesday, since I don't have classes until 7pm and it's supposed to be in the 60s and really nice out. I don't know if my truck has the original motor in it either, it's got the 8th VIN # as a Z, but the engine has the "Spider" injection. . . Is it stock? I thought the "W" engine was the CPI and the "Z" was the TBI. Am I wrong?

[MT-2500]

Originally Posted by 06camarodude

I was planning on checking the fuel pressure as soon as I can find a place to rent a guage, I don't know how to set the base ign. timing, so I might just hold off. . . Wouldn't the problem be evident at startup if it was a timing problem though? I have a couple of other concerns I'm going to address, like a loose wire for the remote starter, the positive power wire is VERY loose on the battery terminal, whoever hooked it up didn't snug it down properly, so I'm going to try and fix that, it ran fine up until that problem occured. The exhaust leak is probably going to be fixed on Tuesday, since I don't have classes until 7pm and it's supposed to be in the 60s and really nice out. I don't know if my truck has the original motor in it either, it's got the 8th VIN # as a Z, but the engine has the "Spider" injection. . . Is it stock? I thought the "W" engine was the CPI and the "Z" was the TBI. Am I wrong?

You are right on that.

Also 94 and 1/2 and 95 models used several different pcm/vcm computer systems and engine and fuel pressure combos.
The 4.3 Z turbo engine used a different fuel pressure and pcm set up to.

Is your pcm/vcm behind glove box or under coolant tank on right front fender well?


You could have a miss match on it if engine and or computer has been changed.

Go for the fuel pressure reading and pcm code check and read out.
And get that exhaust leak fixed. A exhaust leak can throw off 02 sensors and fuel mix.
Good luck