Question about 2004 Pontiac GTO

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Plugs my plugs are blackened and the engine misfires somewhat and backfires thru the carb. am i running to rich and do i need to get a vacuum gage to set the carb to the best vac. reading i can get and what would that be?

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  • redbubba_99 Sep 12, 2008

    i really did not mean a vacuum leak on the engine. some old school mechanics use a vacuum GAGE to adjust the carb. I was told today that as close to 10 inches of vacuum on the gage would be ideal. Thanks

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OK first of all this car has no points, or a carburetor . This is a 2004 GTO that the person is asking about. It has coil packs, one for each cylinder. A vacuum leak could be the issue, but it is pointless to try to chase this down without using the trouble codes. The car will tell you whats wrong. Have the trouble codes checked with a scanner and that will tell you what is causing your issue. You can see a list of trouble codes here.


http://www.wikiauto.com/Pontiac-GTO-2004-2006-Diagnostic-Trouble-Code-DTC-List.ashx

Posted on Oct 09, 2012

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These two comments are spot on also check your points if the dwell is wrong the car will back fire.

check the gap and the condition as worn points case all sorts of problems

Posted on Dec 20, 2008

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For a carbureted engine, backfires can be caused by the valve train timing being way out.
Set your timing properly first, and then move forward from there.
Blackened plugs definitely mean too rich a mixture, and maybe not enough spark to burn it all.
I've never seen a bad vacuum hose cause backfiring, but it will help very much to fix any vacuum leaks you can find.

Posted on Sep 12, 2008

  • Allen Walker Sep 12, 2008

    Those vacuum indicators are useful if you are trying to synchronize dual carbs.

    Nevertheless, backfiring is not usually caused by a malfunctioning carb, it's a timing issue.

    I would set the timing, and move from there. You may have a defective distributor.

    Good luck.

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