apexi

I have a civic CX 92 stock. After the engine warms up, the idle goes high then low over and over again. When it's cold it idle high. No thach so I dont know wat RMP. Does any one know? BAD ECU? BAD Temp sensor? Anyone seen this problem before? Thanks.

bob01721

I have a "feeling" it's not a vacuum leak, unless it's a VERY sneaky one. Vacuum leaks TEND to mess things up REGARDLESS of engine temperature -- tho' not always.

It sounds like it MIGHT be one of those wierd things that happens "occassionally" in Hondas -- air in the coolant. Wait! Don't laugh! Hear me out. Ha! When there's air trapped in the cooling system, an air bubble sometimes gets caught under the IAC valve, which controls the car's idle.

Apparently, the IAC is mounted fairly "high up" in the cooling system, but still below the bleeder bolts. So air bubbles tend to migrate there in a lot of Hondas/Acuras.

Here's how this thing works: The IAC tells the ECU how hot the coolant is around the throttle body. Then, the ECU tells the IAC how to set the idle speed.

When the engine's cold, everything's okay -- the IAC holds a nice high "cold idle" speed 'til it warms up. As the coolant warms up, the IAC tells the ECU and the ECU tells the IAC to back things down to the normal "warm idle" speed. So far, so good.

Then... one of those darned air bubbles moves under the IAC, and so the IAC reports the colder temperature -- the bubbles aren't as hot as the coolant -- and the ECU throws the IAC back to "cold idle" speed. As the bubble and the coolant slosh around under the IAC, it keeps telling the ECU, "Wait! I changed my mind! It's hot now. Wait! No... it's cold." Over and over. So the the ECU's software continuously "hunts" for the right idle speed. Wierd to watch that idle goin' up and down like that. It's all OVER the place. But only when the car's fully "warmed up." It runs just fine while it's cold.

Think about it. You know your car better than I do. Does it seem to you that this is what's happeneing to your car? IF this is your problem, the fix is to get those air bubbles out -- bleed your cooling system. Ha!

apexi

I'd like to thank both of you for taking the time to reply to my problem. I will check for vacuum leak and try flushing out the coolant system. The IAC and the TPS have been replaced and the problem still persists. I've tried disconnecting the IAC and the engines stops, but when I disconnect the TPS nothing happens. Will try it again in the morning. Thanks again.

apexi

I'd like to thank both of you for taking the time to reply to my problem. I will check for vacuum leak and try flushing out the coolant system. The IAC and the TPS have been replaced and the problem still persists. I've tried disconnecting the IAC and the engines stops, but when I disconnect the TPS nothing happens. Will try it again in the morning. Thanks again.

apexi

Ok still no luck.

1. Check for vacuum leak. (none)
2. Bled the cooling system for bubbles. (small hose connected to IAC)
3. TPS Changed.
4. IAC Changed.
5. Disconnected IAC while engine is running (warmed) engine oscillate. (more pronounced when IAC connected.)
6. Reset ECU.
7. IAC has 12V present. (I'm assuming that the ECU is seeing it because the engine idle oscilates)

ECU code still 14. HELP!!!!!!!!

Mista Bone

Faulty FITV, it can be fixed without replacing. Check on one of the Hybrid boards for the fix.

Fatty_1775

having same problem, where is the info on FITV? Cant find any...

Jackson

You are probably right. FITV. Its located under your tb. The plunger most likely came all the way unscrewed. I have never messed with one on a single cam so I can't give you exact details.
I think its like two or three 10mm bolts holding it on the bottom of the tb, pull the fitv off, look inside for a white, plastic plunger. It has a wide slit in it for a flat head, push the plunger down, because it it forced up by a spring and screw it back in. Sorry on the shady directions, I am just typing from the top of my head.


[Modified by Jedi Master, 4:07 PM 7/12/2002]

Fatty_1775

problem fixed, the surging idle was due to the FITV. It wasn't broken at all or unscrewed, it was just dirty, so it was removed, taken apart and cleaned. It still surges a bit, but not really noticable.