# Stumbling start



## polarzak (Dec 1, 2008)

If that car has a heat riser valve in the exhaust, I would check to see if it is working properly.


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## Master of Cold (Aug 7, 2011)

I would start with the idle air control motor.


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## Master of Cold (Aug 7, 2011)

Also make sure the throttle body is clean, and free of carbon build-up


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## cjm94 (Sep 25, 2011)

Pull the vacuum line off the fuel pressure regulator and see if there is any fuel they are very common to go bad and leak causing a hard start fouling the plugs a little.


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## D-rock (May 23, 2011)

Check vacuum lines, probably all old, dried, and cracked


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## johnniebravo (Oct 4, 2011)

Had that same motor in an 89 cutlass supreme and had similar problems. My problem ended up being the fuel pressure regulator.


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## Thurman (Feb 9, 2009)

Fuel pressure regulator common problem with this motor. Do Not put PB Blaster into the intake system. Use a good "throttle body cleaner" to spray into the intake system _after_ you do get it running and up to operating temp. The throttle body will get a coating around the outer edges over time and mileage causing the "butter-fly" of the throttle body to not close completely at idle. This sends a false message to the ECU and _could_ lead to a "stumbling" problem.


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## Bigplanz (Apr 10, 2009)

Vacuum lines were ok. Air filter needs to be replaced. Underside or the air intake cover was wet with gas. Fuel pressure issue is a distinct possibility as it sounds/acts like it is starved for gas. I will pick up some throttle body cleaner tomorrow.


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## reelangler (Nov 18, 2011)

Check vaccum lines, fuel pressure regulator, and did you gap your plugs?


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## Bigplanz (Apr 10, 2009)

Vacuum lines were ok. I did gap the plugs to spec. I suspect a dirty IAC valve or throttle body. The issue disappeared on it's own for now. It'll be back of course.


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## reelangler (Nov 18, 2011)

Does it sit alot?


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## Bigplanz (Apr 10, 2009)

Runs every day. Short strips though. Nothing over 10 miles total in a day.


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## Marty1Mc (Mar 19, 2011)

I would check the FPR, temp sensor, and throttle position sensor.


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