Electrical Issue, Misfire and P0355 Code

[ninety5fiveoh]

Long story short I've been looking for a coolant leak on the back of the pass side head which led me to do a compression and leakdown test as I cautiously suspected a possible lifted head; tests were fine. After completing these tests a few weeks ago, I didn't start the car afterwards or move it, until yesterday. I put the coilpacks and throttle body assembly back together to take the car for a rip, and now I have a CEL p0355 which is for a cyl 5 misfire.

So far I've swapped coilpacks around, which changed nothing. I tried a new coilpack in cyl 5, which did nothing. I tested every positive wire on each coil pack clip for 12v which was normal on every cylinder (11.5v with key on at each). I also tried resetting the computer. The plug on cyl 5 was ever so slightly damp, but nothing alarming. My wideband is also pegged at 22.6:1. I have learned that this wideband is pretty poor, but it has never been pegged like this before.

Symptoms include the CEL, as well as a severe cutting out somewhere around the 2500-2700 rpm range. The car was running flawless before the compression and leakdown tests, so I'm not sure what has changed.

I was with some buddies today and one of them suggested possible alternator failure? I replaced it with a rebuilt unit when I put the motor in last year for what it's worth, and maybe put 500 miles on it. Just more food for thought maybe.

If anyone has any more suggestions of things to check out, or similar experiences, that would be excellent!

EDIT UPDATE: Borrowed a spark tester from a buddy and cly 5 is not getting spark, but is still getting 12v. That means the ground side isn't getting triggered. Thoughts?

 

[hotcobra03]

Just a guess..you might have pinched a wire putting cover on ..

The connectors are known not to click in..

I would test ground signal at engine connector c133 ..the 1 with the bolt..

See if your getting signal there..if you are it's between that and coil

 

[ninety5fiveoh]

Just a guess..you might have pinched a wire putting cover on ..

The connectors are known not to click in..

I would test ground signal at engine connector c133 ..the 1 with the bolt..

See if your getting signal there..if you are it's between that and coil

Thanks for reply. I did a bit more investigation work last night, and came to what seems like a few conclusions. If I'm not mistaken, the trigger wire for cyl 5 (light green/yellow stripe) enters the engine bay through the harness with the clip WITHOUT the bolt, as I couldn't find that wire in the larger clip with the bolt (c133 as you mention), and I did find that wire in the smaller clip.

I checked signal coming from the PCM, which I do have on either side of the clip (back probed and front probed), but I do NOT have continuity between the engine harness side of the clip and the coil plug on cyl 5. This makes sense, as the only thing Ive done to the car since it was running mint until now was a compression and leakdown test which involved moving that harness around quite a bit and probably broke one of the wires.

Do you or anyone else by chance have the wiring diagram for an 03-04 Cobra?

Thanks!

 

[hotcobra03]

http://www.terminator-cobra.com/svt_documents.htm

Scroll to bottom.
Full pc version has wiring diagrams .connector pin outs.and connector locations..

If no pc.. free here

http://www.bbbind.com/tech_database.html

 

[hotcobra03]

Thanks for reply. I did a bit more investigation work last night, and came to what seems like a few conclusions. If I'm not mistaken, the trigger wire for cyl 5 (light green/yellow stripe) enters the engine bay through the harness with the clip WITHOUT the bolt, as I couldn't find that wire in the larger clip with the bolt (c133 as you mention), and I did find that wire in the smaller clip.

I checked signal coming from the PCM, which I do have on either side of the clip (back probed and front probed), but I do NOT have continuity between the engine harness side of the clip and the coil plug on cyl 5. This makes sense, as the only thing Ive done to the car since it was running mint until now was a compression and leakdown test which involved moving that harness around quite a bit and probably broke one of the wires.

Do you or anyone else by chance have the wiring diagram for an 03-04 Cobra?

Thanks!

Sounds like you found proper connector ..

Test showed you have signal at that connector.... but not at coil end..

That's a break in wire..or like I had on cam sensor..a stretched wire maybe..

I used multi meter .unplugged connector. .and back probed from cam connector till I got a good reading..mine was 1/2 inch back from connector. .must of got yanked ..

I'm thinking you did same thing during pulling coils..

 

[ninety5fiveoh]

Sounds like you found proper connector ..

Test showed you have signal at that connector.... but not at coil end..

That's a break in wire..or like I had on cam sensor..a stretched wire maybe..

I used multi meter .unplugged connector. .and back probed from cam connector till I got a good reading..mine was 1/2 inch back from connector. .must of got yanked ..

I'm thinking you did same thing during pulling coils..

Thanks for the link to the shop manual! Yes, it's most likely a broken or stretched wire. I'm going to make a test wire tonight and check for spark.

UPDATE: Thanks for all the information, I fixed the issue last night. The cyl 5 coil wire was broken about 8" from the clip, must've broken by bending it too much when I did the compression and leakdown tests. Soldered in a new piece of wire, good as new!

 

[Slippery Nut]

Thanks for the link to the shop manual! Yes, it's most likely a broken or stretched wire. I'm going to make a test wire tonight and check for spark.

UPDATE: Thanks for all the information, I fixed the issue last night. The cyl 5 coil wire was broken about 8" from the clip, must've broken by bending it too much when I did the compression and leakdown tests. Soldered in a new piece of wire, good as new!

I may have the same problem on number 8. How were you able to isolate a point in the wire 8" from the clip?

 

[ninety5fiveoh]

I may have the same problem on number 8. How were you able to isolate a point in the wire 8" from the clip?

I used a voltmeter to check continuity and back-probed the green/yellow stripe wire with one end of the meter, and probed the coil wire with the other end of the meter. I started probing by the plug and worked my way back an inch or 2 at a time until I had continuity.

 

[hotcobra03]

I used a voltmeter to check continuity and back-probed the green/yellow stripe wire with one end of the meter, and probed the coil wire with the other end of the meter. I started probing by the plug and worked my way back an inch or 2 at a time until I had continuity.

Glad to see you got it with out having to open a lot of harness..

I got issue like this on our tundra..rodent eat half of main wiring harness under brake booster..I had fix it enough to use until time to make room to redo harness..

Bastards got it again just last week