2003 Buick Regal rough idling

2003 BUICK REGAL
150,000 MILES • 3.8L • V6 • FWD • AUTOMATIC
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STEPHEN KARANJA
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I did a head gasket job on this car.had some problems with my rocker arms but thanks to you guys gave some advice on it.i toqued the rocker arms to required 11ft/lbs but did not turn the wrench extra 90 degrees.
reason being I broke two bolts in this process and didn't want to strip the threads.took it to a mechanic who told me I had low compression in two of the cylinders.could be due to not turning an extra 90degrees.
the car drives fine most time its only on idling thing that it runs rough,po300 error code and p118.can I
fix the compression issue without taking the heads off again.could it also be rocker arms not set right.?
Aug 9, 2014 at 6:39 PM
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WRENCHTECH
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The bolts cannot be re-used in this engine. they are one time use.


Installation Procedure

Use compressed air in order to blow oil out of the tapped holes in the cylinder head.
Lubricate the ends of the push rods with new engine oil.
Install the push rods to the same position on the cylinder head.




Install the push rod guide plates.




Install the valve rocker arms.

Notice: This bolt is designed to permanently stretch when tightened. The correct part number fastener must be used to replace this type of fastener. Do not use a bolt that is stronger in this application. If the correct bolt is not used, the parts will not be tightened correctly. The system or the components may be damaged.

Apply threadlocker GM P/N 12345493 (Canadian P/N 10953488) or equivalent to the rocker arm bolt threads.

Notice: Refer to Fastener Notice in Service Precautions.

Install the valve rocker arm bolts.

7.1. Tighten the bolts to 15 Nm (11 ft. lbs.) .
7.2. Use the J 36660-A to rotate the bolts an additional 90°.

Install the left or the right valve rocker arm cover.
Inspect the valve train for noise.
Aug 9, 2014 at 7:42 PM
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WRENCHTECH
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You also have a coolant temp sensor problem that can dramatically change the fuel mixture.
Aug 9, 2014 at 7:45 PM
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STEPHEN KARANJA
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thanks for your help.but my question is,what are the causes of low compression on just some cylinders.the car drives fine above 10mph.runs rough while idling only.it is not overheating or losing coolant.and also new head bolts were used for this job.is it possible to check compression before everything is put together?could the fact the rocker arms were not tightened to specs. cause this problem.
Aug 10, 2014 at 11:21 AM
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WRENCHTECH
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There are dozens of possible causes. You need to correct the ones you know about first. After you have done that do both a wet and a dry compression test to help narrow it down.
Aug 10, 2014 at 11:26 AM
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STEPHEN KARANJA
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thankyou.i"ll do that.
Aug 10, 2014 at 6:40 PM