1990 Prizm/Corolla Idle Speed Issues - Toyota Nation Forum : Toyota Car and Truck Forums

numero9 · 11-04-2009, 05:16 PM

About 2 week ago, my car was nearly stalling out after idling at a light or whatever. Took it to the shop to get the computer read and it showed a MAP sensor error. He cleared the code and said the idle speed was low. After that, everything fine and dandy then a couple days ago, it starts almost stalling out again. Usually, I can just floor the accelerator and it'll go then I'm fine until the next red light, but if someone in front of me takes their time, it'll stall. Starts right up usually after one or two turnovers.

So stupid question -- last night, I disconnected the battery thinking it might have reset the sensors and corrected the idle speed. I don't have access to test the actual speed or whether these things can reset after 10-15 mins. with the battery disconnected. Any ideas? It hasn't stalled out lately, but I want to know whether it did anything.

90 GP · 11-04-2009, 06:06 PM

Check the vac hose that runs to the MAP sensor on the firewall. Could have a leak which would account for low idle and stalling.

numero9 · 11-04-2009, 07:18 PM

Thanks! Will do, but did disconnecting the battery reset those things?

eage8 · 11-04-2009, 09:23 PM

I would imagine you map sensor is on it's way out and every once in a while it throws some bad values so your ECU throws a code and ignores it... resetting your ECU will make it pay attention to it again until the sensor flakes out again.

I'm not certain this is what's happening, but it's a good bet.

numero9 · 12-08-2009, 02:35 AM

After just about a month, it's doing it again. It seems that leaving the battery off for 10 mins. helped.

The mechanic said the Prizm's computer was throwing a MAP sensor error code, but reading around my 4AFE doesn't have a MAP sensor. I did manage to pick up this: http://img30.imageshack.us/i/8942012040f.jpg/ for replacing the old one. If that's not a MAP sensor, what is it? Any ideas on whether replacing that will help fix this problem? I didn't see any vacuum leaks otherwise, and the car ran flawlessly there for a month until it randomly decided to idle out again.

90 GP · 12-08-2009, 04:02 AM

That pic is the map sensor and you do have one. It is located in the middle of the firewall with a vacuum hose going to the intake manifold. Buy a length of hose and replace the one that's on the sensor to see if that helps before buying a new map sensor.

numero9 · 12-08-2009, 12:08 PM

Well I already bought it (I got it really cheap anyway). Now I can't get the damn connections off the old one.

90 GP · 12-08-2009, 06:01 PM

To remove the electrical connector look at the connector were the wires enter. Right above wires is a small black plastic tab. Push down and hold tab while gently pulling connector straight off. May need to wiggle connector side to side to free it up . If replacement part is a orignianl ND (Nippondenso) part cross reference part number on replacment and orignal. If different they could be calibrated for different engine.