96 7.4l Gremlin. I really need help.

[joejak73]

I have a 96 Suburban with big block . What started out as a intermittent skip has gotten worse. You'd be driving, be Just fine. lost a cylinder for a mile, it would come back. In and out. Then that became permanent.
Gave the truck to a shop because I have two jobs and no time. Truck already had new cap, rotor, fuel injectors and plugs, new gas tank, new fuel pressure regulator and filter. I had them put in a new distributor and still nothing. They said all the injectors are getting power. I am totally stumped. I don't know if it's an internal and I don't think its the computer but I just don't know.

Help please.

 

[stutaeng]

You need to diagnose this properly.

How do you know you were losing a cylinder? Was it spark or fuel lost? Likely not compression if it was coming back? Maybe?

And it doesn't sound like the shop properly diagnosed it either. How did they determine those parts they changed were "bad?" It sounds like bad diagnosis and problem is still there.

Unfortunately, intermittent issues are the worst to fix. You need to catch the problem when it's acting up. And if you do parts changing, you "could" find the problem, but you also introduce the possibility of faulty new components, then you are really deep into the water.

If you don't have time, you need to find another shop that's more into electric diagnostics.

 

[joejak73]

I could tell I was losing a cylinder because it would happen while driving. It was pretty obvious. Now, I believe it's cylinder 1 as when the truck was exhibiting this I was able to pull the #1 wire and it did nothing. I pulled # 2 and it was obvious that there was a wire pulled.

 

[Tech]

You didn't mention plug wires or a compression test. Were all the plugs equal? Someone competent with an engine scope should be able to do a power balance test and tell you if all the plugs are firing equally. Don't overlook the EGR system it can overwhelm a cylinder and cause it to drop out under certain conditions. Vacuum leaks can also lean a cylinder out.

 

[joejak73]

Would the EGR system throw any codes that are useful? Compression test from shop said it was good.

 

[Schurkey]

Connect a scan tool, look at the misfire counts.

See what the O2 sensor is showing for the bank with the misfires (Bank 1, if cylinder 1 is misfiring.)

Look at the fuel trims for that bank, too.

Pull the plug, verify the gap and condition. Test the plug wire, check the cap. If the problem isn't ignition, and it's not compression...it's almost certainly fuel. Defective injector, defective injector wiring, defective ECM. Probably not fuel pressure, or all cylinders would be affected. Wouldn't hurt to verify pressure anyway.

 

[Erik the Awful]

Gave the truck to a shop because I have two jobs and no time. Truck already had new cap, rotor, fuel injectors and plugs, new gas tank, new fuel pressure regulator and filter. I had them put in a new distributor and still nothing. They said all the injectors are getting power. I am totally stumped. I don't know if it's an internal and I don't think its the computer but I just don't know.

Find a shop that can diagnose.

 

[Schurkey]

Am I the only one who was expecting this thread to be about a Vortec transplant into an ancient AMC?

 

[Erik the Awful]

Nope, +1.

 

[gwolf]

DTC's?