4.9 stall in gear
07-26-2017, 06:30 PM
#1
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4.9 stall in gear
Hi my f150 4.9 starter to make the following problem: when in neutral or p the engine is bit compulsing in rpm (+-100rpm) but when in drive or reverse idle speed drops to 500-600 rpm (N and P idle is 1100rpm) So the jumping idle I think could be iac. But the low idle I don't know. . I suspect torque converter locked but I don't think the tc of a c6 even lock on normal circumstances... so any advice here please, it didn't pass safety inspection because of this...
07-27-2017, 11:18 AM
#3
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The high idle speed in Park or Neutral, assuming the engine is warmed up, suggests a vacuum leak. The pulsing and/or low idle speed suggests an IAC problem. Assuming from your username, this is an 89 model year - these were prone to fouling the IAC. Pretty easy to remove and clean the gunk with carb cleaner until the plunger ranges freely. Of course, given the age, it is possible the IAC may be on its way out... Suggest to chase any vacuum leaks first.
Good luck, and keep us posted.
Good luck, and keep us posted.
07-28-2017, 01:49 AM
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It has no high idle in park idle was 800rpm at park, with some fluctuation.
In drive or reverse it drops to 400-600, and stalls.
Have adjust throttle position by the screw on the throttle body to keep it from stalling (1200rpm at P/N now).
when idling in drive for a short minute it has a sudden drop but now catches back up.
I know my problem isn't solved this way but I might be able to get through the inspection.
Btw checking vacuum was my first go. But I will check again.
Regards johny
In drive or reverse it drops to 400-600, and stalls.
Have adjust throttle position by the screw on the throttle body to keep it from stalling (1200rpm at P/N now).
when idling in drive for a short minute it has a sudden drop but now catches back up.
I know my problem isn't solved this way but I might be able to get through the inspection.
Btw checking vacuum was my first go. But I will check again.
Regards johny
07-28-2017, 05:31 PM
#5
Senior Member
Ah, OK - misunderstood here - thought the idle speed was 1100-1200 in Park/Neutral before working on it, but it now appears that this was after the adjustment of the set screw...? If so, then suggest the vacuum leak search can be punted.
At any rate, more confidence here that the IAC has a problem - either gunked up or flat-out failing - not able to move fast enough to control the idle speed with stability.
When the problem is resolved, suggest the set screw needs to be put back in its original position - its function is only to keep the butterfly plates from sticking shut in the throat.
Good luck with the inspection challenges, and keep us posted.
At any rate, more confidence here that the IAC has a problem - either gunked up or flat-out failing - not able to move fast enough to control the idle speed with stability.
When the problem is resolved, suggest the set screw needs to be put back in its original position - its function is only to keep the butterfly plates from sticking shut in the throat.
Good luck with the inspection challenges, and keep us posted.