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More gremlins - P0356 and P0720

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Had two codes yesterday. The first (P0356) I noticed right after changing plugs but did not check for codes prior to the swap so can't say for sure if it came up before or after. It didn't throw a CEL. I just picked it up on my Aeroforce when checking for DTCs.

P0356 - Ignition Coil F Primary/Secondary Circuit Malfunction

I cleared it and went out and drove it several miles and bedded pads and it didn't come back. I'm "hoping" the coil just got interrupted initially and I don't have one going bad, or a connector with a short. Rechecked the connection and it was tight.

The second happened within a mile of the car wash and on my way to bed pads. The speedo went dead and then the dash lit up like a Christmas tree although it didn't go into limp mode. Wrench light, airbag and a couple other lights came on. I got a P0720 Output Speed Sensor Circuit Malfunction. I restarted it and the speedo was still dead, then after a couple seconds the signal came back and it was working again. I scanned and got the P0720 and cleared it and restarted. It didn't come back and the speedo worked fine even after going out and bedding pads and driving around for several miles and restarts.

We put it in the air because I heard an exhaust leak and was afraid I was frying a wire. Found both header to mid-pipe clamps were pretty loose, but no physical signs of an exhaust leak (soot, baking :)) Also, the harness leading to the trans had come loose from it's retainer so zipped it back up but it didn't look damaged.

Hoping this doesn't rear its head at the track next weekend. We still haven't found the P0611 issue and it still rears its head when holding steady mid-range throttle, particularly when getting on the interstate. https://trackmustangsonline.com/index.php?topic=7537.0

I guess my car's just "special" :)
 
Well if there's anyone that can find a "fault" in these cars it's you. Hopefully you don't see them again and your next track day is uneventful.
 

ArizonaBOSS

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Jeez. Never really heard of a coil pack going bad--might want to check any harnesses running by the headers for burns etc.

BTW I blew up that driveshaft :)
 
ArizonaBOSS said:
Jeez. Never really heard of a coil pack going bad--might want to check any harnesses running by the headers for burns etc.

BTW I blew up that driveshaft :)
Yea I did but nothing visible. Found the header to midpipe clamps loose which was causing the exhaust leak I could hear but no burns anywhere. Hoping the coil was just a post spark plug change phenomenon and won't come back.

Nice :) Did you do it in grand style with a cloud of white smoke when the grease hit the exhaust? What are you going to for a permanent fix?
 

ArizonaBOSS

Because racecar.
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cloud9 said:
Nice :) Did you do it in grand style with a cloud of white smoke when the grease hit the exhaust? What are you going to for a permanent fix?

Yup, let out a big puff of smoke at Willow Springs, didn't find out that it was from the driveshaft until a month later when I saw it spitting fluid on the exhaust on the dyno.

Got a Dynotech 3.5" shaft in there as of last week, works great so far! No vibrations up to 120 at least.
 

ArizonaBOSS

Because racecar.
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hahaha yes I know 120 is not super high for judging this effect; but that's the only option I had so far.

Laguna Seca in July I will probably be able to hit 130 on the front straight...did 127mph last time.
 

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