1988 Plymouth Sundance Idle Dies

1988 PLYMOUTH
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ESGAROTH
  • MEMBER
  • 11 POSTS
My car has been having trouble keeping a smooth idle. The car will start and then die immediately. If I hold down the gas for a few seconds and let go it will idle smoothly and I can drive it just fine. Sounds like the idle air control motor right? I get an error code confirming this so I took out the iac motor to see what would happen. The car should idle at about 3000 rpm. It doesnt. It gets to about 2000 rpm and idles erratically. After a few seconds it smoothes itself out and goes up to 3000 rpm and then dies. After this I get a code for the map sensor. This seems normal as with such an extreme vacuum leak it should tell me that something is wrong. Car has a new fuel pump and filter. Fuel pressure is fine at 14.5 psi. Compression is 135+ in all 4 cylinders. All 4 plugs are getting spark. I noticed that the brand new spark plugs I put in were covered with carbon (rich mixture?) so I changed the oxygen sensor. Fuel injector seems to be running smoothly as far as I can tell. Any other ideas?
Jan 23, 2006 at 5:53 AM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
Hi:
Chances are there is a vacuum leak that you heven't found yet. Make sure there isn't a leak near the intake. Also, check the lines around the intake.

Let me know what you find. Just FYI, the idle should be around 900 RPM's.
Mar 20, 2009 at 3:30 AM

Suggested Repair

Inspect for an unfound vacuum leak near the intake and check the vacuum lines around the intake. Normal idle should be about 900 RPM, not 3000 RPM.

Conversation Summary

The owner of a 1988 Plymouth Sundance reported that the engine starts and dies unless the throttle is held briefly, after which it idles and drives normally. They suspected the idle air control motor based on a code, but removing it did not produce the expected high idle and later set a MAP sensor code. Fuel pressure, compression, spark, the oxygen sensor, and injector operation had already been checked. The expert advised looking for a vacuum leak near the intake and around the intake lines, and noted that normal idle is about 900 RPM.

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