need new IAC?

97 escort lx wagon 5 speed manual 144,000 miles

had the P1504 code come up. read to test the IAC to let car warm up and then while engine is running, unplug IAC and car should stall. car didn't stall. instead of spending $75 on a new one I cleaned it up and put it back in. the idle has smoothed out but when I unplugged it the car still didn't stall. my question is, does it depend on the model and type of IAC if it stalls or not or does it not matter and since it didn't stall, I still need to just get a new one. It's only been since last night so the code hasn't come back up yet but the idle is better.

97 escort lx wagon 5 speed manual 144,000 miles

had the P1504 code come up. read to test the IAC to let car warm up and then while engine is running, unplug IAC and car should stall. car didn't stall. instead of spending $75 on a new one I cleaned it up and put it back in. the idle has smoothed out but when I unplugged it the car still didn't stall. my question is, does it depend on the model and type of IAC if it stalls or not or does it not matter and since it didn't stall, I still need to just get a new one. It's only been since last night so the code hasn't come back up yet but the idle is better.


I'd wait a couple hundred miles before doing anything. If you reset the code it will take the computer probably somewhere between 50-150 miles for everything to reset. If the code doesn't come back then cleaning it probably took care of the problem. I know in many cases cleaning them will take care of problems with them.

If you unplug the IAC, that just means it wont move. So wouldnt the car keep running at the same idle speed as it had been? My understanding is that the IAC stays in the position where the computer left it, unless the computer tells it to move again.

It should stall if you take the connection loose while the engine is running. My 97 is this way. Check the wires going to the IAC motor for voltage. Could be the computer is faulty. As mentioned, before it will stay at the last setting the computer programmed for it. If it is the computer, replacing the IAC will have little affect on it. I would disconnect the battery for 5 minutes to set the computer back to default values, then drive it to have the computer "relearn" the new parameters.

the car was running when I unplugged it.

At that mileage, you should replace the IAC anyway, The Wells one at Autozone works fine and isn't very expensive.