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1978 Chrysler LeBaron Convertible Base

1978 Chrysler LeBaron Convertible
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October 30, 2012, 8:48 pm

Bob S

Question: No idle on a cold start, then hyper-fast idle when in neutral or park after warmup

My neighborhood (certified) mechanic has replaced the Throttle Position Sensor, the Idle Air Control Motor/Module and finally, on his suggestion, the ECM since the old one appeared to have some burned circuit terminals. End result: no change in behavior. Starts easily cold but won't stay running until warmed up. Then okay as long as in gear, but in N or P it revs up to warp 9 rpms.

November 3, 2012, 10:06 am

Ron W
Expert Mechanic

Sounds like a vacuum circuit/leak issue.

The easiest way to find a leak in the vacuum circuit is with a smoke machine. With the engine OFF, pump smoke into the intake manifold through a vacuum port and wait. The smoke will come out wherever there is a leak.

Since the electronic components are already replaced, that's where I'd start.

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