Stumped by high idle while moving
12-05-2013, 08:14 PM
#1
Stumped by high idle while moving Within the last month, my car has developed an idle issue that only presents itself when the car is in neutral and I'm coasting towards a stop light. I clutch in, revs drop to about 1,600 RPM, and hold there steady until the car stops rolling. The second the car stop rolling, the revs fall to ~850RPM and hold steady. Clutch in or out doesn't seem to matter, exhibits the same symptom, plus, cruise control works so I don't suspect the clutch position sensor. I performed the throttle body relearn procedure several times, reset the ECM, no change.
It doesn't happen every time, but it does happen a majority of the time. Trouble has shown up about the same time the ambient temp started to drop, but we've had several warm days and the problem still persisted. From time to time I also feel a lack of engine breaking when off throttle, but still in gear. I suspect the engine is still being fed power (high idle point) and as a result is not slowing the drivetrain down like you would normally expect. The only similar complaints that I've found in old threads seem to be caused by dragging clutches, or a bad idle all around. Nothing quite like I'm experiencing. Any ideas?
It doesn't happen every time, but it does happen a majority of the time. Trouble has shown up about the same time the ambient temp started to drop, but we've had several warm days and the problem still persisted. From time to time I also feel a lack of engine breaking when off throttle, but still in gear. I suspect the engine is still being fed power (high idle point) and as a result is not slowing the drivetrain down like you would normally expect. The only similar complaints that I've found in old threads seem to be caused by dragging clutches, or a bad idle all around. Nothing quite like I'm experiencing. Any ideas?
12-06-2013, 02:53 PM
#5
On The Tree
Join Date: Oct 2012
Location: Nashville, IL
Posts: 158
Likes: 0
Received 0 Likes
on
0 Posts
High idle like this is usually due to some kind of vacuum leak post MAF. Check all the vacuum lines, make sure clamps are tight on the intake tube after MAF. You can use starter fluid and spray where the gaskets are, connections, intake manifold, throttle body, etc.. to help pinpoint where the leak is. If starter fluid gets in the combustion chamber the idle will smoothen out and you'll know where the problem is.
12-25-2013, 01:19 PM
#8
no, not yet. Too much time wrapped up in getting the car ready for the audio install over Christmas to troubleshoot anything else. My guess is a vac leak, and when I have the time, I plan on spraying starting fluid around the intake track and listening for idle changes.
01-13-2014, 04:01 PM
#11
Update to my original issue. The car sat at my audio installer's shop for nearly a month over the Christmas and new years break. The battery died and was recharged, the car also spent a fair amount of time with all power disconnected. I eventually had them install a new Optima Yellow top. Since getting the car back, the high idle issue is gone and the RPM's behave normally when I coast to a stop.
Weird.
Update II:
The hanging idle issue returned a few days after the battery swap. I had a spare MAF sensor on hand, swapped it, and have not had the issue since. My original MAF was causing the problem.
Weird.
Update II:
The hanging idle issue returned a few days after the battery swap. I had a spare MAF sensor on hand, swapped it, and have not had the issue since. My original MAF was causing the problem.
Last edited by Fweasel; 11-28-2014 at 10:02 PM.
