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Old 12-29-2010, 10:05 AM   #1
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boxster misfiring and running rough

Hi can anyone help? 1999 boxster had been losing power,disconnected the maff and went for short run and car ran fine. Fitted new maff and went run for 70 miles and car ran like a dream. started her up this morning and she was rough and misfiring, disconnected new maff and still running rough. I had a spare coil pack so changed them one at a time but still very rough. I did notice that a couple of the coil packs had slight cracks in the plastic. Would appreciate any help,thanks, Sreven.
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Old 12-29-2010, 09:51 PM   #2
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Get the fault codes read (Durametric is a good choice) and this will show which cylinder(s) are faulty.
Untill you can read the faults, you are guessing at what the problem is.
For instance, you could have 2 faulty coil packs, and with the weather you have been having in the UK, you can chase your tale tracking down the fault......
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Old 12-30-2010, 08:48 AM   #3
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Car would not tick over this morning so put old maf back in and drove to the garage. By the time I got to the garage car was running ok. Fault codes read misfire in all 6 cyllinders due to coil packs, cant see them all going at once.Has this happened to anyone else?
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Old 12-30-2010, 09:09 PM   #4
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Yes it can happen - age and temperature tend to crack the insulations in varying degrees and once moisture enteres the equation, voltage mistracking will follow.

You can find that one coil is delivering 80% of the voltage to the plug and losing 20% through the breakdown in insulation but still fire the cylinder OK - the next plug along could be losing 30% of its prescribed voltage giving a CEL and reduced performance (missfire).
If you live in a harsh enviroment the coils have a shorter lifespan than in a warm dry climate.
I guess you should replace all 6 coil packs - you should feel the difference in performance too.....
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2001 MV Agusta F4.

Last edited by Steve Tinker; 12-30-2010 at 09:11 PM.
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