OK. Just out of the blue one day last week, the idle on my car started to surge, from about 800rpm to 1300 (back and forth). I have a 94 Del Sol with the B16A3 motor.

I took the air filter off, cleaned it well, that seemed to help a little bit, but then it came back. I took the IAC (Idle Air Control) Valve off and cleaned the screen thats in that. That didn't help. (tho someone told me it could be stuck open?)

I took the copper plate off the back of the Fast Idle Valve and tightened the screw inside that down. That seemed to help. At a stop, it would surge 2-4 times and then go back down to a higher idle of about 1000 instead of 800.

I reset the ECU, that just made things worse, surged at every stop and didn't stop surging.

I flushed to coolant, twice, and refilled.

I took apart the throttle body, cleaned it off, made sure that FI valve was tight again and reinstalled it, tried to adjust the idle screw (which looks as tho was never adjusted before because of the sealant around it. That didn't seem to help either.

I have yet to check the vacuum lines, thats gonna be a bitch, and it might be the TW sensor. (water temp sensor below the distributer)

I don't get a check engine light, and it does not do it when the motor is cold.

Can anyone give me their advice?

Thanks...

-Josh

 

couple others to try...check your timing and your plugs, and it could also be your o2...

 

It's most likely a vacuum issue.. Also try playing around with the idle adjusting screw located on the TB - this sometimes calms down the IACV....

 

I did actually, I tried adjusting the screw, while engine was running and off. But it didn't do anything.

 

Hmmm... I know how you feel - when I installed a Y8 intake manifold on my D16A6 motor, the idle was going all crazy exactly like yours... Only after it warmed up. I replaced the IACV and now it purrs like a cat. Of course my old IACV was kinda bent, lol.

 

That's an older motor, the fast idle sensor is prolly gone to the B16 in the sky... happened on my LSVT soon after installing the head.

 

Ok...so maybe my fast idle valve is dead, or the IACV is dead?

 

What would happen if I unplugged my map sensor? Could I have a bad map sensor or throttle position sensor?

 

yes i could very well be the TPS or possibly a MAP sensor, but usually it's vacuum leak or Idle valve. i wouldn't rule the TPS or MAP out. check the voltage and such to be safe. sometimes it's something stupid that went crazy for no apparent reason.

 

I think i'm going to get my engine bay cleaned off tommorow because its rather filthy, so checking for leaks wouldn't be easy if I did it the hard way...

Anyone know a good way to check for leaks?

 

The way to check for vaccum leaks is to make sure that all 2 of your vaccum lines have good connections to the manifold. The get some pliers and squeeze each hose at the manifold. If there is a change, that hose has the problem. Most likely you have a bad iacv.

 

So there are only two vacuum connections that would affect the idle?

I'll check in the morning, but are these two connections easy to find?

I'm really too new to this stuff..

 

I've tweeked with the idle screw...
blead my coolant a couple times...
reset the ECU twice...


while messing around, I unbolted the iAC while the engine was running, the motor started to sound like a fighter jet, RPMs bounced from 1K to 2K, Shut the motor off.

Put the IAC back on, unplugged the sensor, replugged it back in. Started the car, no surge...

Went around the block, at all stops, no surge.
Came back to the home...no surge..
went around the bloack again, no surge...
coming into the apartment, it surged maybe but hardly once and went back down to a low idle...

I believe I have a bad IAC valve....