"Rodan" wrote: (1992 Buick Roadmaster 350 TBI).
Idles at 1200-1500 RPM cold or hot, runs rough, feels
exactly like a stuck automatic choke, but there is no
choke - it's fuel injected. The (ODB-I) shows no
malfunction codes. I removed the IAC valve (it looks
like new) polished the pintle and seat and reinstalled it
with no change in performance. I will remove the EGR
valve tomorrow. Is there something else I should check?
Check the gasket between the throttle body and
intake manifold. I'll bet it's sucked in.
Well, I checked everywhere for vacuum leaks, including
under the throttle body, and didn't find the problem.
As usual, I decided to start throwing parts and money
at it. I bought a new IAC valve first, thinking it might
lower the idle speed, so I could then look for the miss.
Miraculously, the IAC valve fixed everything; the idle
dropped to the correct 550 rpm and the rough running
So why am I thanking aarcuda? Because he took the
time to offer a suggestion from his experience which
I might never have considered. I have been spared
many dollars and skinned knuckles by the knowledge
shared here by alt.autos.gm posters. And I do the
same for others here even though I am sometimes
ridiculed by professional auto technicians.
Thanks again to aarcuda, and to all those who have the
courtesy and the courage to offer help to others.