| Subject: | Check engine light. |
| Question: | I have a 91 Mitsubishi
Galant, AT. Last weekend, the check engine light went on. The
idling was rough during startup and sometimes became stable after
a few mins. But sometimes, engine just died out. It also happened
when I waited at a stop sign. I used a analog multimeter and
read three error code: 13: Barometer sensor Error 15: Idle control motor postion sensor Error 25: Air temperature sensor Error. I followed the manual and checked those sensors, they appeared to be ok( but I was not sure since the test was not exhaustive). Anyone have similar problem before? Any suggestions? A shop quoted $125 for diagnosis. I am not sure if I should go for it. By the way, the autozone stores I asked didn't offer free checking engine line anymore. But I think all they did to just help you read out the codes. Now every time I start the car, I have to keep press the gas to prevent the engine from stopping. After the car warms up, it looks ok but the "check engine" light is on all the time. Please help me. |
| Answer: | Tiewen, I have heard of similar problems to this before. And you are correct, some AutoZone stores stopped giving a "full" diagnostic read of your car's computer (ECU), but they can help you read the codes. Most AutoZone's I've visited in New York state still offer code reads for free still. Your Barometer and Intake Air Temperature sensors are both located
in the Mass Air Sensor (MAS) unit. That is what your air filter sits
on. If that was your only problem, I would suggest getting a new
MAS unit. But because you mentioned you also read the code for your
Idle Speed Control motor and that you used a Mulitmeter to check
those, I would advise you read this article: I've been getting dozens of questions in the past couple months with very similar problems. In many cases, it was the ECU causing the problem. A remanufactured ECU can cost you around $125. That's about the same price as quoted for your diagnostic test. And odds are, even if your ECU is not causing these problems now, your ECU will fail in the future. Mitsubishi is aware of this problem, and my end up making a recall on this since the appearant design flaw is only lasting about 10 years. That's why I believe I keep getting so many question about these strange problems. If you want to be positive that these are the only codes appearing
and that these codes are consistent, you should try to give you ECU
a hard reset. Simply unplug your negative battery cable for about
15 minutes, then reconnect it and read the codes again. That way
you can be sure. |