I have a problem with an up and down idle when the engine is warmed up. I have replaced the IDLE CONTROL AIR VALVE and the FAST IDLE THERMO VALVE, but the problem continues.

What would you suggest? What about the THROTTLE POSITION SENSOR?

Please give me a hand.

Thanks.

 

map sensor.

 

vacuum hose leak somewhere?

 

clean the EGR? seafoam it?

 

the cheapest and easiest thing i figured out how to do to fix that problem is , go to the junk yard find the same year, and get the whole top half of the intake manifold with the senors on them and then a new gasket, fixed my problem real fast and simple

 

Along with all these, another thing to check is air-bubbles in the cooling system. The IACV & FITV are confused by occasional air coming thru their hoses.

 

check the idle with an external source.
or just turn the idle down.

 

did you check to make sure you pcv valve to make sure it still rattles?

 

Thanks for all your valuable advice. In the end it turned out to be the THROTTLE POSITION SENSOR.

But let me tell the whole story. Based upon the advice of a few experienced Honda mechanics, this seems to be the way to go.

1. Start with a vacuum leak, like a knocked off vacuum hose. No solution?

If the engine is COLD when the problem occurs, 2. continue with the IDLE AIR VALVE -- clean it, test it, or replace it. While you are at it, test the FAST IDLE THERMO VALVE also, if your model has one. Still unstable?

If the engine is WARM when the up and down happens, 3. next try the THOTTLE POSITION SENSOR on the throttle body. (You can not usually buy the sensor alone, but the whole throttle body only, so buying it used saves a lot!) Still no luck?

4. h: Test or replace the MAP sensor, located in a control box often. Still doing the rollercoaster?

5. Clean out the EGR valve or replace it. Still stubborn?

6. Look at the advice given by all the contributors to this thread or take out a loan and head for a dealership garage.

Hope all this helps. .

 

You may be interested to hear the ending of my battle with an uncooperative engine idle.

Yes, the replacement of the Throttle Position Sensor solved the "up and down" aspect of the idle problem. But the engine continued to idle rough, especially when cold. Along came help from Tech 444 on justanswer.com, who suggested that the EGR ports in the intake manifold could clogged up with carbon and sent a service bulletin with repair instructions. Yes, that procedure helped, but not totally.

Well, I continued to read my trusty Haynes manual about the EVAP system (the canister setup for catching raw gasoline vapors) and went ahead and tested it -- which also proved to be defective. Sure enough, after repairing the unit, the darn rough idle FINALLY CAME TO A HALT.

The bottom line of my experiences is this -- THREE systems had been at fault: the TPS, the EGR, and the EVAP. So keep plugging away fellow rough idle mechanics -- especially if you own a 1990-1993 Accord known to be trouble prone in this regard.

(I am a witness here that it does not always pay to buy a "great used car with low miles" from a nice church-going old lady, etc, etc.)