5.7 TBI stalling please help

[tpcolson]

I have a 88 suburban with a 5.5L TBI in it. It starts hard, idles rough, and under acceleration it jumps, stalls, sputters, and chokes all at the same time. I checked the ALDL and it returned 42..knock sensor. So I replaced that and the cap/roter. Still doing the same thing. The fuel spray coming out of the injectors is conical, no dripping. Any ideas? Thanks.

[jdr2008]

This may sound trivial, but please check the throttle body gasket, I had a similar problem and that was the cause, Its also a cheap fix and worth the time to check it out.

[tpcolson]

Originally Posted by jdr2008

This may sound trivial, but please check the throttle body gasket, I had a similar problem and that was the cause, Its also a cheap fix and worth the time to check it out.

The gasket between the TB and the manifold? What goes wrong here? Gasket disintigrate and get into the plenum?

[Rbraczyk]

get yourself a vacuum tester

[Fireplug]

1988 5.5L ????? you mean 5.7L?? Chevy 350 Engine
The knock sensor code is a result of the problem not the cause.
Have you done the basics complete tune up ? cap rotor, wires, plugs, fuel filter, checked and cleaned EGR.
Checked for any vacuum leaks ? What is the fuel pressure reading??

[jdr2008]

Originally Posted by tpcolson

The gasket between the TB and the manifold? What goes wrong here? Gasket disintigrate and get into the plenum?

Yes, the gasket between the TB and maniflold, and yes my gasket broke down, causing the same things you are descibing. Im just giving you an idea of what may be wrong, and its easy to check it out.

[65chevy]

is sounds to me like it may be a clogged EGR, stuck open, also it sounds like possibly a clogged fuel filter

[J-Ri]

I don't wanna scare you, but it could possibly be a small coolant leak in the head gasket. I had an 87 Astro with the 4.3L TBI that had all the symptoms you described. Since the 4.3 is the 5.7 with 2 less cylinders, I thought I'd mention this.

[kenny-1907]

I agree with jdr2008 , check your TB gasket. I had an 88 full size Jimmy with the 5.7 TBI in it with the same problem and it was the base gasket. There was a piece only 2" of the gasket left.