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Juan Crespo
Juan Crespo, Tech Trainer
Category: Ford
Satisfied Customers: 1526
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Mustang GT: 02 mustangGT. Plugs good, new coil packs, getting

Customer Question

02 mustangGT. Plugs good, new coil packs, getting P0316 and also misses on 1,3,5, and 6. And compressor clutch drops out when this is happening._ while CEL is flashing Any ideas?
Submitted: 2 years ago.
Category: Ford
Expert:  Juan Crespo replied 2 years ago.
Hi there. Welcome to our site. DTC P0316 means there is a misfire on cyl 6 during start-up - is this the only code? If yes, how do you know it's also misfiring on 1, 3 and 5?Compressor clutch coil is energized by the PCM through the A/C relay. If the PCM detects a type A misfire (CEL flashes), it will stop energizing the A/C relay.Eventhough coils and boots are new, the possibility exists of those being incorrectly installed or deffective, so more testing is required. I can guide you through all the diagnostic steps, but you'll need to provide the tools and skills to use them. In addition to an assortment of hand tools, we might also need a scan tool capable of reading PIDs, a scope (or a multimeter capable of reading frequency and MIN - MAX voltage), ignition and fuel pressure testers and a Noid light.
Customer: replied 2 years ago.
I have an SPX scan tool that tells me the codes. Saturday I had P303, P305, and P306, indicating misfires on those cylinder. I also got the P316 occasionally. After I changed the 3, 5, and 6 coil packs I thought I had 6 fixed, but 3 and 5 were still throwing codes. I did a physical inspection of the plugs on 3&5, and found boot debris in # ***** which I cleaned out. I test drove for about 10 minutes, no codes. The next day, drove 20 minutes to work, and got 5 codes. 1,, 3, 5, 6, and the P0316. I put new coil packs on last year, bought from Summit racing. I figure they were going bad, so I ordered some new ones(MSD brand). I am beginning to think part of the problem is getting the boot seated properly on the plug....
Expert:  Juan Crespo replied 2 years ago.
I agree with you. Seating the boot properly on the plug is crucial (I use lots of WD-40), otherwise you'll have spark jumping to the head and creating misfires. Issues like that are easy to identify when you look at both primary and secondary ignition patterns on a scope screen. That's why I tell all my customers who plan to work on their own cars to get themselves a basic set of diagnostic tools. Even if you initially spend $1000 on a used scan tool capable of reading PIDs and a two-channel scope, you'd be amazed at how much money you can save vs. paying a competent mechanic to do it for you. Best Regards.
Expert:  Juan Crespo replied 2 years ago.
Hi again. Just checking to see if the information I provided helped you solve your issue. If it did, then kindly accept and rate my answer now. If it didn't, please reply so we can keep working.Best Regards.