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View Full Version : Check engine codes clearing question..M20



Gregs///M
01-19-2009, 10:34 PM
So I've been having this serious misfire issue with my M20 for a long time and I finally got the problem to go away tonight.

My car would idle fine at startup and run perfect until the engine reaches normal operating temperatures. Then I would get poor idle, hunting idle, weak acceleration, and stalling at stop lights. Once stalled, it would take several turns of the starter to get the car to start.

I've replaced a slew of engine components including injectors, AFM, plugs and finally tonight I was able to replace the Coolant Temperature Sensor.

Here is where my question comes up. I reset the ECU by disconnecting the battery on most of the component replacements. But when I replaced the Coolant sensor I started the car up and did not replace the codes. My problems continued so I assumed there was something else wrong with the car.

I also found a leaking with my Throttle intake, it was a 90 elbow connecting the Idle control valve. I sealed that up then finally reset my ECU.

After resetting my ECU, I took it for another test drive and its runs beautifully. NO idle problems at all.

My question is this. Even after installed the Coolant sensor with a new spare, will the motor continue to run poorly? Is resetting the ECU, causing the motor to idle fine now? Perhaps the small leak on the throttle was at fault? I doubt this because i caused the leak by breaking the seal during initial inspection AFTER i notice the symptoms.

What are you thoughts? Can not resetting the ECU cause the problems to continue even though the sensor is brand new?

grecobeemer
01-19-2009, 11:23 PM
How long after 2 mins of idle or 30 miles of driving? My problem was the same. Change most of the same parts, coolant sensor, plugs, AFM. Appears the AFM was the culprit and cured it.

Gregs///M
01-19-2009, 11:29 PM
I drive the car for about 15 minutes of neighborhood driving. My problems always arise as soon as normal temperature was reached. I changed the AFM but that did not repair the problem.

grecobeemer
01-21-2009, 09:18 PM
Is your car running better now?

Gregs///M
01-21-2009, 09:46 PM
Its running better but the rough acceleration is still there at normal temperatures. I replaced the throttle position sensor and I'm thinking oxygen sensor and ignition wires next.

grecobeemer
01-21-2009, 09:56 PM
Yeah I was driving my E34 the other day and remembered that when I first got it, it had your problem. I changed the O2 sensor and it worked fine for years then the AFM went out on it. I forgot to post it, but yeah O2 sensor might be the culprit.

Gregs///M
01-21-2009, 11:02 PM
OK, good to know. I don't think the O2 sensor has ever been replaced. It is probably good that I go ahead and replace it anyways. Thanks for the info, good looking out.

grecobeemer
01-23-2009, 06:07 PM
That's why we're all here. Let me know if it worked.