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Old 11-26-2007, 07:41 PM   #1
MBrearley
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P0304 rough idle

2001 Pontiac GrandAm 3.4 with about 160,000 miles.

The check engine soon light came on recently and after having it checked out, it's coming up P0304, misfire in cylinder #4.

When the car is in park, it seems fine. When I put it in drive and just sit there, the car kida bucks (definatelly feeling the misfire). When I accelerate, it hesitates slightly (very slightly) at fist, then accelerates fine.

I changed the wires and plugs. The other suggestions were coil, vacuum, injector and high or low fuel. There's no whistling noises at all, so I'm fairly certain it's not a vacuum leak. I'm guessing it's either an injector or coil. What's my best option to check? I can't imagine that the fuel injectors would be very easy to replace, what about the coils? Would a bad coil cause a misfire on a single cylinder?

Thanks...
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Old 11-26-2007, 07:56 PM   #2
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here yah go I did some searching for you.
Code PO300
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Old 11-26-2007, 07:57 PM   #3
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My suggestion would be to pull the wire off of only the plug and stick like a plastic ended screw driver where the wire connects to the plug and if it arcs then you know its not the coil which only leaves the injector that could be sticking. might be kind of dangerous but nothing that can kill
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Old 11-26-2007, 07:58 PM   #4
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could be that coil pack...accually thats probably what it is.. i run accels
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Old 11-26-2007, 09:14 PM   #5
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Quote:
Originally Posted by MBrearley View Post
2001 Pontiac GrandAm 3.4 with about 160,000 miles.

The check engine soon light came on recently and after having it checked out, it's coming up P0304, misfire in cylinder #4.

When the car is in park, it seems fine. When I put it in drive and just sit there, the car kida bucks (definatelly feeling the misfire). When I accelerate, it hesitates slightly (very slightly) at fist, then accelerates fine.

I changed the wires and plugs. The other suggestions were coil, vacuum, injector and high or low fuel. There's no whistling noises at all, so I'm fairly certain it's not a vacuum leak. I'm guessing it's either an injector or coil. What's my best option to check? I can't imagine that the fuel injectors would be very easy to replace, what about the coils? Would a bad coil cause a misfire on a single cylinder?

Thanks...
It's rare to find a coil misfiring for only 1 cylinder. But you can easily check it by switching it with one of the other coils and see if the misfire moves to another cylinder. If that doesn't fix it then I'm pretty sure you have a bad injector. They aren't that bad to change. Once the UIM is off, they are easily accessible. You don't even have to disconnect the fuel lines. Just be sure to relieve pressure on the fuel rail.


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Knock it off cause your not helping with anything.
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Last edited by Sprucegagt; 11-26-2007 at 09:16 PM.
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Old 11-26-2007, 09:33 PM   #6
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bullsh!t ive had it 4 times now on #5 or #1 never both at the same time
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Old 11-26-2007, 09:50 PM   #7
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yea im having the same problem with the 3rd cylinder... i have new plugs.. new wires.. have run injector and top engine cleaner, this weekend im going to physicly clean the 3rd injector and i will let you know how it turns out
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Old 11-26-2007, 10:23 PM   #8
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bullsh!t ive had it 4 times now on #5 or #1 never both at the same time
So you've changed that coil 4 times? If so then you've got something else wrong.
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Old 11-26-2007, 11:14 PM   #9
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Quote:
Originally Posted by Sprucegagt View Post
Knock it off cause your not helping with anything.
Well I'm trying to help.....but who cares. I type P0304 in the search and 5 threads popped up.....so thats helping!
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Old 11-26-2007, 11:46 PM   #10
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ive replaced damn near everything include my injectors and the ICM wires, plugs, im outta ideas
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Old 11-26-2007, 11:57 PM   #11
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You didn't answer my question. Did you change that coil pack 4 times?
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Old 11-27-2007, 12:02 AM   #12
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yes
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Old 11-27-2007, 12:05 AM   #13
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It's rare to find 4 coil packs go bad in a row or were you using accel coil packs?
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Old 11-27-2007, 12:18 AM   #14
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all accel 4 within 3 years
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Old 11-27-2007, 12:26 AM   #15
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I bet that's your problem and it may be due to installation error. Check the bottom of your coil packs for two indents made from the mounting pins on the ICM. They may have punctured the coil case which will cause a short.

New PCV valve, sea foamed and accel coil packs-now have problems

FYI, use the stock coil packs. All the aftermarket coil packs are really no better than the stock units.
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Last edited by Sprucegagt; 11-27-2007 at 12:34 AM.
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Old 12-01-2007, 08:34 AM   #16
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Quote:
Originally Posted by Sprucegagt View Post
I bet that's your problem and it may be due to installation error. Check the bottom of your coil packs for two indents made from the mounting pins on the ICM. They may have punctured the coil case which will cause a short.
I had an older GrandAm that had a coil pack go out twice in a row. It ended up being the housing causing the issue.

Well, I'm going to replace all the spark plugs later today. If that doesn't help, I'll replace the coil packs. Is it recommended to replace all of them or can you replace just one? I'm really hoping that it's not an injector, although I have my suspicions that it may be. Why can't this happen in the warmer months, I don't have a heated garage... :-(
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