02 4.6 misfire...help me

aaron175617 · July 7th, 2006, 06:22 PM

Hello all
I have an 02 mustang 4.6L 2 valve, supercharged with a misfire on number 3 cylinder. The car has been supercharged since new and I haven't done anything to it prior to it developing the miss. The code said that number 3 cylinder was missfiring. I changed the coil-on-plug coil, sparkplug and injector on #3 cylinder; checked the compression and vacuum (both well within specs); reset the computer and number three still misfires. The #3 sparkplug looks as though it is getting fuel but the fuel does not seem to burn (it looks kinda wet and shiney). I pulled the coil off and hooked it to the old sparkplug and grounded the plug, had someone turn the engin over and it sparked on the plug very well, (OUCH). Anyway, I don't claim to be all that bright and I can't think of anything else it could be.

Anybody else had this problem or have any ideas? Thanks a bunch Aaron

mdvaldosta · July 7th, 2006, 07:07 PM

Do a compression test on that cylinder, maybe you damaged a piston, valve, or head gasket (not very likely). Is the engine still stock? How much power was being made?

aaron175617 · July 7th, 2006, 08:01 PM

The car makes 495 rwhp, it is stock but it is a Saleen S281E with chip tune and pulley makes about 13lbs of boost. I did a compression test on the #3 cylinder and the others and they all looked good, I don't rembember what the compression was. I have been fooling with it for about three months now.
It was running fine before this miss started, drove it home one day and then the very next day went to start it and it had the miss.

I thought must be a fouled plug, changed them all and still missed. Been changing things ever since, and still #3 miss. I moved the injector to #1 and got a new coil for #3, but still #3 misses. I also removed the chip out of the computer and put the car back to the stock tune. Could the computer be messed up? Could it do this? I have an 01 Saleen I guess I could swap out the computers and see what that does. What do you all think?
Thanks for the replay.

mdvaldosta · July 7th, 2006, 08:22 PM

Well, you've covered all I can think of. Maybe Casper or another one of our techs have some ideas.

Casper98GT · July 8th, 2006, 12:40 AM

Ok, so number 3 cylinder is dropping out. Coil on plug was replaced, injector was swapped. We know youre getting fuel and spark in that cylinder because you tested it. If youre getting spark and fuel in a cylinder but its still misfiring you have other issues. I was going to say check the wires going to the plug because i have seen damaged wiring harness. But you have already beat me to it with the spark tester. How did you find out it was a cylinder 3 misfire ? What was the exact code if you got the system checked and was there any other codes. There is a slight posibility that it would indeed be a pcm issue. But you cant be sure without doing pinpoint tests to the pcm itself and you have no access to the test procedures. Hell im a ford tech and i have no access to Saleen wiring/shop manuals. Because we are not a saleen dealer. If all else fails go to a Saleen dealer. Im not sure where youre located. But if i had the shop manuals and wiring diag's you could give me a call and figure it out.

But get back to me about the codes.

Casper

aaron175617 · July 14th, 2006, 09:25 PM

The code was P0303 and it was read at Auto Zone a local parts store. The car is in Phoenix.
Thanks a bunch
Aaron

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July 7th, 2006, 06:22 PM	#1
aaron175617 Newbie Join Date: Jul 2006 Posts: 3	02 4.6 misfire...help me Hello all I have an 02 mustang 4.6L 2 valve, supercharged with a misfire on number 3 cylinder. The car has been supercharged since new and I haven't done anything to it prior to it developing the miss. The code said that number 3 cylinder was missfiring. I changed the coil-on-plug coil, sparkplug and injector on #3 cylinder; checked the compression and vacuum (both well within specs); reset the computer and number three still misfires. The #3 sparkplug looks as though it is getting fuel but the fuel does not seem to burn (it looks kinda wet and shiney). I pulled the coil off and hooked it to the old sparkplug and grounded the plug, had someone turn the engin over and it sparked on the plug very well, (OUCH). Anyway, I don't claim to be all that bright and I can't think of anything else it could be. Anybody else had this problem or have any ideas? Thanks a bunch Aaron

July 7th, 2006, 07:07 PM	#2
mdvaldosta Maintenance Man 2002 Mustang GT 11.47@120.58 Join Date: Aug 2005 Location: Valdosta, GA Posts: 3,944	Do a compression test on that cylinder, maybe you damaged a piston, valve, or head gasket (not very likely). Is the engine still stock? How much power was being made?

July 7th, 2006, 08:01 PM	#3
aaron175617 Newbie Join Date: Jul 2006 Posts: 3	The car makes 495 rwhp, it is stock but it is a Saleen S281E with chip tune and pulley makes about 13lbs of boost. I did a compression test on the #3 cylinder and the others and they all looked good, I don't rembember what the compression was. I have been fooling with it for about three months now. It was running fine before this miss started, drove it home one day and then the very next day went to start it and it had the miss. I thought must be a fouled plug, changed them all and still missed. Been changing things ever since, and still #3 miss. I moved the injector to #1 and got a new coil for #3, but still #3 misses. I also removed the chip out of the computer and put the car back to the stock tune. Could the computer be messed up? Could it do this? I have an 01 Saleen I guess I could swap out the computers and see what that does. What do you all think? Thanks for the replay.

July 7th, 2006, 08:22 PM	#4
mdvaldosta Maintenance Man 2002 Mustang GT 11.47@120.58 Join Date: Aug 2005 Location: Valdosta, GA Posts: 3,944	Well, you've covered all I can think of. Maybe Casper or another one of our techs have some ideas.

July 14th, 2006, 09:25 PM	#6
aaron175617 Newbie Join Date: Jul 2006 Posts: 3	The code was P0303 and it was read at Auto Zone a local parts store. The car is in Phoenix. Thanks a bunch Aaron

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