Why is my 90 silverado not idling good?

Asked by Nov 16, 2013 at 10:07 PM

Question type: Maintenance & Repair

My 90 c1500 with a 5.7 is idles fine
wen cold but at operating temp it
starts to idle up an down spittin an
dies. Ses light came on an gave me
code for the cts which i changed no
fix.now i have changed the
tps,cts,mapsensor,02sensor,iac,
coil,distrib, cut the cat off,checked
egr,fuel filter, fuelpump not even a
year old yet.did pressure test on fuel
but both times from two diffrnt fuel
gauged they both leaked at the
fittings do i gave up. An i rebuilt the
tbi. If i rev it up it clears up but then
idles real low then back up an down.
Plz help im pretty mechaniclly
inclined but this has me scratchn my
head .

3 Answers

Sounds to me that a vacuum hose has fallen off and the intake is suckin' air~....could be the connection to the fuel pressure regulator...could be to the egr...could be to the environmental controls~ I'd say an IAT sensor, but I'm not sure this vehicle has one~

always replace the awful black rubber (chewing gum and coal tar) with silicone that never dries out, cracks or swells...these are perfect and totally reliable~

Iv checked all hoses. But none broke or loose.

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