Almost stalling at idle

[crsgmc]

1996 K1500 5.7

I have rebuilt most of the truck. Most parts are new. I got a code for EGR a while ago and took it out and cleaned it. A few months later the code was back. I replaced the EGR with AC Delco. When doing that I sprayed some throttle body cleaner it the port for the EGR. The EGR code did not come back on, but it ran very rough. It stays on high idle when coming to a stop. It does drop down 10 seconds after you have stopped. When sitting at idle it is running a little high at 900. It always idled at 700 before. After idling for a few minutes it will drop to about 300 to 400 and almost die. It will then recover only to do it again in a few minutes. Is it possible that the cleaner gunked up something. I think I am smelling fuel out of the exhaust. Thanks for any help you can provide.

New EGR, IAC, Throttle position sensor, Engine: new GM crate with 17,000 miles

[speedygonzales]

Sounds like you have a vacuum leak that the PCM is trying to correct by closing the IAC. Then the idle drops and it reopens the IAC and so on.

The only suggestion I can give is don't forget the hoses aren't the only place it can leak from. The intake gaskets can also.

Don't get the OEM plastic intake gaskets if you replace them. Get the metal Fel-pro units.

A good scanner could help you find the issue but it still would not pinpoint the location if it is indeed a leak.

[hugger6933]

Spray carb cleaner around the manifold and the vac points. also remember there is a solenoid for the egr and they are troublesome

[crsgmc]

When I replaced the engine, I used the Felpro metal gaskets. The intake is new, when I installed the engine. The old one was really pitted up and I could not get it to seal correctly.
What hoses would you think might be leaking? I am not sure which hoses are vacuum hoses.

Because this started right after I sprayed cleaner in the EGR port, I really suspect something connected with the cleaner. I might try cleaning the intake.

[crsgmc]

Thanks to all that replied. I figured that since the problem began when I replaced the EGR, I would start there. I went to remove the EGR and it almost fell to the floor. Even though I used a torque wrench, I broke one of the ears that the bolts go through. I also realized that the metal is sinsider type medal. It is ground up metal that is pressed, glued, and or heated to make the base. This kind of metal, in this case is not very strong. I could not get the part locally so I flux core welded the ear back on. I did very small welds to the part so it would not heat up too much. That ear is now probably stronger then the original. Put it back together and it runs fine. Because the base was broken it let in lots of air confusing the PCM. Causing lots of problems, including fuel vapors out the exhaust.

[Palf70Step]

Glad you found the issue. I remember just making a block off plate to replace mine cause it was all cracked up. Never thought about welding the cheap thing.

[speedygonzales]

Originally Posted by Palf70Step

Glad you found the issue. I remember just making a block off plate to replace mine cause it was all cracked up. Never thought about welding the cheap thing.

In the 96 and later, the PCM checks the function of the EGR by checking a change in the O2 readings when it changes the state of the EGR. If he just blocked it off, it would throw at least one code. If he removed it completely without putting something like a load resistor in place, it would also fail a continuity check and thus light the dreaded CEL. I don't know about others, but any light that is on that shouldn't be would drive me crazy.