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1990 Chevy Corsica

Tiny
CORSICA3.1
  • MEMBER
  • 1990 CHEVROLET CORSICA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 77,700 MILES
Would a knock sensor help an engine that has a rough idle? I've tried everything. EGR, O2 sensor seemed to help with mileage, a good cleaning of the Idle Air Control valve, PCV valve is fine, and the computer was replaced before I even got the car. I'm hoping its note a fuel injector, but I've been looking around and heard that a knock sensor would do the trick. Any ideas on what it might be?
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Saturday, January 10th, 2009 AT 4:55 PM

4 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Have you checked for vacuum leaks? Have you checked fuel pressure?

Joe
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Tuesday, January 27th, 2009 AT 7:13 PM
Tiny
CORSICA3.1
  • MEMBER
  • 3 POSTS
The fuel pressure is fine as far as I know. Would that have to do with the pump in the tank? I've also been replacing vacum hose cracks all over the place. What do I do know
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Wednesday, January 28th, 2009 AT 9:05 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Hi:
A rough idle is most likely the cause of needing a tune-up or a vacuum leak. My concern is the 3.1L are known for having intake gasket problems. Check around the intake for any evidence of coolant leaks. Some people will actually spray starting fluid around it with the engine running and if there is a leak, the engine RPM's will increase. My only concern is the danger of starting a fire if the starting fluid hits an exhaust manifold or other item that is really hot. If I had to guess, it would be an intake gasket problem.

As far as the knock sensor, they are designed to advance the ignition timing to the max point right before you get a ping or knock from the engine. That is the point the engine will probide the most performance and fuel efficiency. I questions if it would cause a rough idle.

Let me know what you find with the intake gasket. Most common point of leak would be the passanger side front corner of the engine.

Joe
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Wednesday, January 28th, 2009 AT 10:01 AM
Tiny
CORSICA3.1
  • MEMBER
  • 3 POSTS
There was a small air leak on the gasket from the EGR valve to the engine. That has been taken care of and it seemed to help a bit. As far as I can tell there is nothing wrong with the intake seals anywhere. No sign of coolant leaks as you mentioned, but I did have to replace the coolant temperature sensor awhile back. Could it just be getting to hot?
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Thursday, January 29th, 2009 AT 8:59 AM

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