My coworker has a 94 accord sedan with the SOHC 4, she has had a problem with it idling erraticly in park/neutral. Idle will rev up to 2k, then quickly fall to 1k and repeat. I unplugged the grey plug on the top of the TB, which I assumed was the idle air controller. This caused the problem to go away for a few seconds, but then it started again. I searched and read a lot about the fast idle valve. Did I unplug the fast idle valve? Does that sound like the problem?

 

It may have been the MAF sensor (mass airflow) that you unplugged... I'd probably start by cleaning the IAC valve and EGR valve, and Throttle body since that's a cheap easy thing to do and may very well resolve the problem...

 

This problem could be caused by any vacum leak; but here is some info.
The FITV [#14 in the attached pic] will act stupid if the coolant is low or air is trapped in the system.
First thing is to have a cold engine and burp the coolant system thru the 12mm bleed screw at the T-stat housing, with the radiator cap off.
If you get a bunch of air out, try warming up the engine to see if the problem is gone.
If not open thecover of the Fast Idle Thermal Valve and inside you'll see a 'split' screw with a brass cone sticking thru it, turn that screw in a couple turns. If you turn it in too far you lose fast idle on cold start.
You should not hear the air bypassing [loud hissing]when the engine is warmed up. The cone is forced into the seat by Thermal expansion.

The Idle Air Control [#19 ] can be tested by unplugging it and the idle should drop approx. 200 RPM.
If you want to clean the IAC I'd recommend to remove it and spray out the air passages, and gasket screen with Berrymans B-12 carb cleaner. Flood it with cleaner and shake it up, dump it out a few times.
The EGR system doesn't come into play at idle speeds but if you want to clean it out. I'll throw in the link;
http://members.troublecodes.net/hond...5AccordEGR.htm



[IMG]local://upfiles/5417/06C8ACE8813441DE87A1B428B7A92146.gif[/IMG]

 

I unplugged number 21 in the diagram...what is that? IAC is 19, whats 14?

 

#21 would be MAP (manifold absolute pressure) sensor, right? This car probably doesn't have a flow sensor (MAF).

#14 (FITV) is fast-idle thermo-valve. It's job is to open an air passage for higher idle speed while the engine is cold. As the engine warms up it's SUPPOSED to close completely. It has coolant flowing thru it, so if there's air trapped there, it won't know that the engine is warmed up.

 

I was looking at a 2000 EX today that had that same problem. It had been on the lot for overa month and had not been driven. We let it run for about ten minutes at idle and the problem went away.
For now?...

 

edit...nevermind

 

No air in the bleeder...
Ended up the coolant port into the FITV was clogged up with crud, FITV was a couple turns loose, and the screen in the IAC valve was completely blocked. Runs great now