3.8 engine trouble - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-08-2011, 10:33 PM   #1
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Default 3.8 engine trouble

Got a 97 GP with a 3.8 engine. The engine is not running correctly. When I take the air filter housing loose and let the motor draw non filtered air, it sounds and feels like it is struggling to get air. I am also having vaccum pulled through the oil fill cap. When you take the oil cap off,it relieves the motor and the motor no longer acts like it is struggling to draw air,but still doesnt run right. I changed the pcv valve and maf sensor, but nothing changed. The engine isnt running right all the while and I think I may have a clogged cat convertor causing excess preasure in the cylinders. Am I thinking right on this, or does anyone else have any advice on these issues. I am relly scratching my head on this one.



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Old 10-08-2011, 11:23 PM   #2
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The struggle to get air is usually a sound made by the Idle Air Controller, as it is letting some air through. This is normally a noise blocked out by the stock air box. Many people with after market intakes deal with this noise, and it is prevelant especially on cold mornings.

Usually, I check the cat convertor by disconnecting the downpipe and rocking the block. If it is clogged, the problem will go away. Be careful if you do it, as you will be running with open exhaust, and the noise is usually quite horrific.
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Old 10-08-2011, 11:24 PM   #3
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The noise you describe is also a common complaint when the o-rings are not properly installed on the pcv valve.
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Old 10-09-2011, 12:35 PM   #4
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A vacuum at the oil fill cap is generally the PCV valve, O rings or spring. A clogged CAT would cause a over pressure, not a vacuum. Take the fill cap off and put your hand over it. You will know if there is vacuum.
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Old 10-10-2011, 11:38 PM   #5
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O rings lookgood and there is no spring on pcv valve-never has been one
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Old 10-11-2011, 07:13 AM   #6
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If the car isn't supercharged, there is a spring that sits in the cap. If it is charged..there'* one that sits above the pcv
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