Idle problem and stalling 1998 F150
I hope one of the forum member can help me !
My 1998 F150, V6 4.2 Automatic has been acting up.
When standing still at traffic lights (with the transmission in Drive) etc the engine is not running at a steady rpm but fluctuates constantly and results in the engine stalling.
The car bucks when this happens (due to increased RPM).
If I put the car in neutral the rpms sort of stay at the same level.
Driving the car there seem to be no problem.
The mechanic who looked at this problem advised me that the Mass Air Flow Sensor was broken (as the OBD code was pointing in that direction) and replaced it but then told me that the problem was not gone so he thinks it is the PCM that is faulty.
Not to thrilled to spend another bundle on a guess.
So I have been checking out this forum and found some other problems mentioned which seemed similar with some advice on how to deal with it.
This afternoon I checked the IAC , removed it but is seemed pretty clean.
Then I disconnected the battery for 10 minutes, left the car idle for 10 and drove with it for another 10 so the PCM would relearn. Problem is still there after that.
Again removed the IAC and sprayed some W40 in it, reinstalled and started up. For a moment the engine , while in drive, seemed steady but then it started changing RPMs again.
I hope someone has an idea what causes this or advice on how to further troubleshoot it.
Many thanks !