Possible misfire in the engine? - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 04-16-2015, 04:26 PM Thread Starter
 
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Possible misfire in the engine?

It's kind of hard to explain, but I got a 2004 GTO, mostly all stock besides the guy put a K&N air filter on it. But whenever I have it in drive(sitting at a stop light or just not moving in general) it's not a consistent timing but you can feel a jump or like the engine gets slugged. It don't do it while it's in park though. It almost is like it gets punched in the gut and hicups just for a secound but then is back to normal for a certain all mount of time, and then will do it again after a little bit longer. The car drives amazing and nothing else is wrong with it, this is the only problem and was wondeing if anyone knew anything about it. I was planning on changing plugs/wires and see where that took me first.. Any opinions would be appreciated I could possibly get a video later after work if needed.

Last edited by GcwRyan; 04-16-2015 at 04:29 PM.
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post #2 of 5 (permalink) Old 04-16-2015, 07:59 PM
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Garage
Just a thought but it sounds like it's an automatic. Smell the trans fluid

2004 Blk/Rd M6
6.3 litre LS1

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post #3 of 5 (permalink) Old 04-16-2015, 10:15 PM Thread Starter
 
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Okay, yes it is an automatic, sorry!
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post #4 of 5 (permalink) Old 04-18-2015, 06:15 PM
 
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Ryan, good advice from svedesvede to check trans as when you put the car in park it takes the load, the trans off. A trans via the torque converter adds a little drag or load. But a car can misfire only under load.....and not necessarily be the trans

These modern cars are very susceptible to low fuel pressure problems, like it should be 60 PSI and it is 52PSI and you start to see hiccups or drive ability issues.

Also modern cars all have a misfire monitor, avalible thru a scan tool. Any garage will have one that can log in from a connection under the dash and read the misfire monitor. That helps isolate it if it is on one cylinder or a broader problem. Like low fuel pressure, that has to be checked with a fuel pressure gauge.

Easy things to check is ensure all plug wires are clean and tight, take out spark plugs if you can and check the condition gap etc. when the car is running you can put your finger on the fuel injector and feel it working, if one is not vibrating You have a place to start, bad FI, bad wiring, bad computer drivers of injector.

Have you ever changed the fuel filter?

But likely you will need a scanner and a fuel pressure gauge. After as svede said, check tranny fluid first, is it low? Real dirty? Make sure it is right.

Low fuel pressure feels like a lot of weird stuff. But maybe you know that you have a new fuel pump and clean filter...

Good luck
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post #5 of 5 (permalink) Old 04-19-2015, 07:57 PM Thread Starter
 
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I have not changed the fuel filter yet, I just got it recently. I've checked all fluids and everything of that nature and that's fine. I've cleaned a couple parts and sensors but I'm going to buy some new plugs and try that if I need to. I'll do the other steps you said to try, I've put an engine code checker on it, but there were no codes, or anything else wrong with the car... Thank you very much for the long reply I'll take them all into consideration, have a good day.
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