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GM Bob
GM Bob, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 993
Experience:  30 plus years. experience as GM technician, ASE Master Technician and GM Certified.
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Did scan. Says number one cylinder misfiring. Put in new

Customer Question

Did scan. Says number one cylinder misfiring. Put in new plug but used existing wire. Seems to run smother but engine light flashed. Over. 30 mph. 2004 Pontiac Grand Prix 3800. Non turbo
JA: Thanks. Can you give me any more details about your issue?
Customer: Yes when I accelerate can detect some vibration. Temp gauge got just into the hot range while I was having a conversation. I shut it off. Removed radiator cap. There was a slight pause then antifreeze spewed out all over engine compartment. I put in new antifreeze. Not overheating but ran rough after that. Drive about 1500 miles this week and so just now replaced plug on number one cylinder. Existing plug looked dry black. Gap was like three times the gap on new plug. Runs better but sight vibration upon exhilaration
JA: OK got it. Last thing — Pontiac Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 10 months ago.
Category: Pontiac
Expert:  GM Bob replied 10 months ago.

Hello my name is ***** ***** I can help.

Have you tried swapping the spark plug wire? To see if the misfire moves to the other cylinder.

I'm think you got the cylinder to hot and now the one of the valves are bad.

If the misfire does not move with the wire. Need to do a compression test and a leak down test

Customer: replied 10 months ago.
Haven't tried switching the wire. What would be the problem you suspect ?
Expert:  GM Bob replied 10 months ago.

If the wire does not help. Do this first

I think the exhaust or intake valve are not seating. Need to do a compression test and a leak down test.

May have to remove the head and have it recondition.

Expert:  GM Bob replied 10 months ago.

Did you need more help?

Let me know if I was helpful.

Thank you