2002 Saturn idles @ 1800 rpm

Reg

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#1
My 2002 Saturn SL1 1.9L OHC, Standard Tran. ~125000 km. presently idles @ 1800 rpm.
The original problem started a couple months back. An engine code for the Cam shaft sensor, I couldn't find one the Dealership said there isn't one- try changing the plugs, cables and possibly the coil pack including the module. All three replaced, the coil pack and module used. The OBD ll then identified two engine codes - P0301 cylinder 1 misfire detected and P0507 idle control system RPM high. After deleting the codes the cylinder 1 misfire has not returned but the P0507 returned and the idle does not drop below 1800 rpm at idle, it idles down to ~ 600 rpm when the clutch is engaged.
Looking for advise.
Reg
 

Paul

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#2
Remove the idle control motor,its located at the bottom of the throttle body.Clean it and the bore it sits in.More than likely you have some carbon in there thats not allowing the pintle to reduce the amount of air entering the engine when it should.

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Reg

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#3
I removed the idle control module and cleaned both it and the bore with carb. cleaner. There was some carbon build up, but cleaning it made no significant change. I appreciate the suggestion and any further advice you may have to offer.

Thanks,

Reg
 

Reg

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#4
The idle continues to run ~ 1800 rpm. I used an idle control motor tester, the pintle appears to move freely, and will idle up and down (not below 1800) when the engine is running. I've tried removing and plugging vacuum lines, looking for remote air leaks. At this point in time I suspect a cracked intake manifold or damaged gasket, but I'm not able to confirm this.
The cylinder #1 misfire code returns when at operating temp. I have tried exchanging plugs and coil towers, the code continues to read cylinder #1 misfire.
I wonder if having a poor air fuel mix due to a cracked manifold or leaky gasket would cause the cylinder misfire?
 

Gus

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#6
Spray some carb cleaner in that area and see if there is a change in idle....
 

Reg

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#7
Fixed by replacing the intake gasket.
The RPM dropped to 600, misfire gone, 0 engine codes and she is running smooth!

The intake gasket had shifted partially covering the port of cylinder #1, it also had separate along the bottom edge of cylinder #3. The intake did not appear warped and the nuts were tight with the initial removal. I do not think the problem originated from poor factory installation considering the shape of the gasket and how it fits over the studs.
My only conclusion is that the intake has some movement - design flaw due to poor support/ balance of intake ?
Tx for advise.
Reg
 

ironhead

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#8
They all move some. It`s expansion and contraction from heating up and cooling down. The head heats up quicker and cools down slower than the intake manifold, so there`ll always be some movement. The gasket is designed to allow that movement, but after enough time, they all wear out.
Glad to hear you got it fixed,
Guy