Car idles high in the Morning

Tiny
POINDEXTER
  • MEMBER
  • 1987 OLDSMOBILE 98
  • 3.8L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 185,000 MILES
The car idles high in the morning and will not go down until I drive it after five minutes or turn it off. After five minutes then turn it back on and then it runs normal.
Tuesday, February 19th, 2019 AT 4:17 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi and thanks for using 2CarPros.

First, how high is the idle speed? Often times, this is caused by an engine vacuum leak. On this model vehicle, it is common for the intake manifold gaskets to leak. If unmetered air leaks into the engine, it can cause a high idle. Now, as the engine warms up (five minutes), the steel will expand on the engine and it could cause the leak to stop and the idle to return to normal.

With that in mind, the first thing I suggest is to check for a vacuum leak. Here is a link that shows how it is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you decide to try the test and use a carburetor cleaner to check, remember it is flammable. Avoid spraying it directly on any component which is extremely hot such as an exhaust manifold. I always keep a fire extinguisher close by.

Try this and let me know what you find.

Take care,
Joe
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Tuesday, February 19th, 2019 AT 6:44 PM

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