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Ivan, ASE Certified Master Technician
Category: Chevy
Satisfied Customers: 4871
Experience:  ASE Master Tech. 20+ years experience. 9 years self employed. Expert on AUTOLAB Radio Show
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2003 pontiac grand am: GT...Diagnostics..Cylinder..misfiring

Customer Question

i have a 2003 pontiac grand am GT. Diagnostics indicates Cylinder #5 misfiring. Replaced plug #5 and complete wire set. Still "bogging" out/misfiring. Oil change in May 2008 (synthetic 7500 mi) Checked oil when it bogged, was 2 qt. low. No leak underneath vehicle and no burning smoke or smell. Checked oil pan and filter for tightness...all good. I am guessing a cracked cylinder, head gasket or valves. Any ideas? If so, how much for repair?
Submitted: 9 years ago.
Category: Chevy
Expert:  Ivan replied 9 years ago.

HelloCustomer You've ruled out spark plugs and ignition wires. Next step. check for spark at that ignition wire. Then your next step, swap coil packs so the coil pack for cylinder 5 is somewhere else. See if the misfire moves. Finally suspect a faulty intake manifold gasket or fuel injector. These manifold gaskets are horrible for leaks. Spray some carb cleaner around that #5 cylinder mating surface and see if the engine responds. Fuel injectors are very common for plugging up and not allowing enough fuel to enter the engine. I hope this helps. As far as for cost, they vary tremendously between the repairs. See if you can rule some things out and then we can focus on the remainders.


Your JA Expert,


Customer: replied 9 years ago.

Just so you can get a better idea as to who you are speaking to...i am a single mom without a whole lot of funds for repair. Now that we got that out of the way...Smile I am new to learning about my engine. If the coil pack for #5 was bad, wouldn't #2 misfire as well (since it fires on the same pack)? Further, a guy friend of mine tested the spark on #5 and got an orange glow (of course, that was before replacing the plug).

Expert:  Ivan replied 9 years ago.
Ok, hello single mom. I understand, but you know some stuff, so you've got some knowledge, so I'll keep myself from getting too technical. It is possible to have cylinder 5 fail and 2 continue to have spark. The spark that comes from these coil packs should be a solid blue/white spark. The deliver a lot of power (and can give you quite a wollup). It's relatively easy to move the coil packs around and see what happens. If there is no change, we can rule that out, but if it changes, you found it and it was easy. It's not always that easy but it does happen. The fuel injector is a little harder to pinpoint because of the design of the engine. We use a piece of equipment that can operate the injector, and we use it to see how much a fuel pressure guage drops when we operate it. By comparing it to other cylinders, you can see how much it's flowing, but even with that it's not always clear. You almost have to eliminate things and narrow it down to that if everything else is good. One thing you and your friend should do is a compression test on the entire side of the engine. If all pressures are Ok, you don't have a damaged cylinder. As far as the color of the spark, check a good cylinder and compare the quality of the spark with the bad cylinder. If they look the same, it's probably Ok. Start with these things and let's start eliminating more things. We'll try to keep the money in your wallet and not in the car if we can help it. By the way, how many miles is on your car and am I correct by assuming your car is a 3.4 liter V6?
Customer: replied 9 years ago.
Yes it is the 3.4l V6 and it has just a little over 87,000 miles on it.
Expert:  Ivan replied 9 years ago.

Start with swapping the coil packs and checking compression, also while you or your friend is at it, spary the carb cleaner around the mating surface of the intake manifold. Let me know what you find, and we'll go further.



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Customer: replied 9 years ago.

I will do. Thank you so much Ivan, I am glad to have found this site. More importantly, you were very easy to understand and you also gave some insight on troubleshooting I can do on my own before having to ultimately take it in. After I/we try your suggestions is there a way I can contact you rather than having to go throught the whole explanation again or do i just have to re-explain and reask my question in the future? Thanks again!



Expert:  Ivan replied 9 years ago.

This link will stay open, just add to it and I'll get it. I'll be here when you need me.