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Posted on Aug 29, 2010
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My 91 oldsmobile 98 runs rough in idle but when driving run smooth.

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Jonah Oneal

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  • Oldsmobile Master 14,092 Answers
  • Posted on Aug 29, 2010
Jonah Oneal
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ROUGH IDLING CAUSED BY VACUUM LEAKS AT VACUUM HOSES OR INTAKE MANIFOLD VACUUM LEAK.DIRTY INJECTORS.WEAK FUEL PRESSURE EGR VALVE STUCK OPEN.

Duane Wong

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  • Posted on Aug 29, 2010
Duane Wong
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Rough idle is a very common problem on 4 cylinders, but I believe the 98 Regency has a 6 cylinder in it, right?

Sometimes the coil packs get iffy, and sometimes the EGR Valve gets a leak in it causing a rough idle.

When the accelerator pedal is depressed, it can change things so that the engine seems to run smoothly.

However, I would look for codes to see if anything intermittent is occurring in the engine that may need attention.

The OBD-I scanner can help to diagnose the problem, if anything is out of specifications on the engine in question.

The owner will have to find a technician that has such a scanner.

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  • Posted on Sep 28, 2011
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Would you rather it run rough on the freeway and smooth at idle? It's a 91 Oldsmobile. If it gets you to your destination, I'd celebrate.

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