20N!N

Bought my car in August and replaced just about every seal under the sun (sans head gaskets and main bearing seals).

I was experiencing a hard idle with a severe stumble. When cold started, the engine would crank but would go pluh pluh, pleh and then die if you didn't manually accelerate it up to a higher idle speed. I chased this thing every which way. I replaced the plugs, wires, distributor, cap, rotor, checked the TPS sensor, everything. Turns out, it was the IAC valve.

I still have a rough idle, feels like maybe a miss(?) and I'm still learning a LOT about engines (call me the neophyte's neophyte!) and would appreciate any suggestions that anyone could contribute to that. More than that though, I just want to thank all the many people who have made suggestions on the board, and Zap in particular for pointing me in the right direction!

:hail:

DENN_SHAH

iTrader: (1)

have you checked for vacuum leaks? flushed the injectors?

Morley

When you changed the IAC did you clean out the idle passages in the throttle body?

20N!N

Morely: I wiped the throttle body off and did a "dry-clean" without the help of cleaners and such. Think that I should pull it back off and get after it with some cleaner?

Denn: I have checked for vac leaks, didn't find any but that doesn't mean there aren't any. Most of the hoses are dry and brittle and plan on replacing them soon. I have not flushed the injectors at all. I have run cleaner through them (ala STP "jet fuel") however, which seemed to help - at least for that tank!

Morley

Valvoline makes a cleaner called "Synpower" carb & throttle body cleaner. This stuff dissolves carbon like a hot knife through butter. Remove the IAC and spray it in the bore it was in, directing it at the holes in there for idle air and soak it good, reinstall the IAC and fire it up. If you get an improvement, you may want to remove the TB and give it a good through cleaning.

rgarcia63

Did you set the minimum air idle speed, and TPS adjustment?
If so which instructions did you follow?

Vader

Just so we're all on the same page, do you have a rough idle, or wandering idle? Rough would be an occasional misfire with overall vibration, either with or without RPM variation. Wandering idle would be a relatively smooth engine operation (no vibration) but with no consistent RPM.

The reason I ask about the semantics is that an IAC problem can cause a wandering idle, but it isn't likely to cause a rough idle. That would be more likely due to a fuel delivery, compression, or ignition problem.

Morely is exactly correct. While the IAC was removed, you should have cleaned the bore where it resides. The seat of that bore comprises half of the IAC "valve" assembly. At least it should be easier to remove this time. Whatever you do to clean the TB, avoid getting any solvent cleaners on the TPS.