GS470

The car is a 2007 Z06 with heads, cam, headers and a tune. It's got 13k miles on it now. I bought it 4 years ago. It was one owner, bone stock with 8k miles on it and I had the mods done nearly immediately. The car hasn't given me any trouble until now.


When I took it out for the first time this year, I got about one block and lost a cylinder. I don't see how this can be related, but I'll mention it anyway. The cylinder died when I was sitting at a stop sign. I turned the steering wheel and accidentally bumped the windshield wiper stalk and turned on the wipers. It was at this moment I could tell something changed. The car had a miss from that point forward.

I brought it home and plugged in my obd II analyzer and it showed a P0303 error (generic misfire error on #3). I then put my timing light on cylinder 3 and it wasn't firing, but the adjacent cylinders are fine. I tried swapping both the coil pack and then the plug wire between cylinders 3 and 5, but cylinder 3 is still dead. Damn. I was hoping it was one of those things, but no luck. Car was in storage in my attached garage all winter, but I don't see any sign of rodents chewing on any harnesses.


If it's not the coil pack or plug wire, any thoughts on what would cause this?

HK770

Plug, Compression,injector ...my best

Gator6977

The plug? There's not much else, unless the coil pack isn't getting signal to fire. Then BCM maybe? I'm not 100% on where the signal comes from, sans distributor.

GS470

It's definitely an electrical issue on #3 because there is no signal being picked up by the timing light in the #3 plug wire, even after swapping the plug wire and coil pack between cylinders. I didn't think a bad plug would prevent a signal through the plug wire, so I didn't try swapping plugs, but it's an easy thing to do.

If that's not it, I gotta think it's somewhere in the harness or connectors. Or the PCM/ECU. Any tips to help narrow it down? Feels like it's going to get much more challenging at this point.

subfloor@centurytrans

Disconnect the harness going to the entire bank of coil packs and look for a pushed in pin. I had the same thing happen last year and that ended up being the problem. It'd also explain why the problem remained if you only changed the coil pack on #3.

BlindSpot

Look at the harness to the coil. do a continuity check on the pins to the coil. It is highly unlikely an ECU will fail on one cylinder.

Yokesc5

GS470

I'm going to take a look at the connectors for both the bank and the coil pack. Now the dumb question. How do I do a continuity check on the pins?

Edit: Just saw the post about the Google search. I'll check that out tomorrow.

GS470

Ok, so I did the search on the LED tester. I currently have a simple, standard (non-LED) 12 volt test light pen. Any reason I can't use it to test each pin on both the coil pack and driver's side harness connectors? And should I expect to see some current for all pins during the cranking process? In other words, how will I know if I found a problem? I'm not familiar with the details of how these ignition circuits work.

Thanks for your patience and help.

subfloor@centurytrans

Honestly, you're overthinking this. Simply disconnect the main plug and look at the pins - if it's the same problem as I was having it'll take all of 3 seconds to identify which pin is the issue.

Yokesc5

GS470

I just took a close look at all pins/connectors and I can't see anything that looks incorrect. All pins are intact and the female side looks fine from what I can see.

I honestly missed the comment about a dead plug preventing a signal through the coil/plug wire. I didn't think that it worked that way, but I'm now going to try swapping plugs and see what happens.

C5 Diag

A C5 Guy here !!...Pink wire at the coil is the feed wire. Light blue is your control wire to the PCM/ECU (pin 77), the brown wire is the Low Ref.(ground) from PCM (pin 78)...all the power wires (fuse 12) and ref. grounds (pin 78) are all tied in together (1,3,5,7) on the left bank coils if you look at the wiring diagram...and you'd check the wiring by backprobing the harness !!

This might help with checking the positive/control side !!!...easier than spelling it out...from the "Jedi Master of engine diagnostics !!

GS470

In my last post I should have said I didn't catch the "hey dumbass" nudge/reminder to check the plug. :-)

But fortunately I did finally pay attention, because that took care of it. I swapped plugs and the dead cylinder followed. New plug and the problem is gone! Thanks to everyone for their help and patience.

OregonMike

Love the simple ones

GS470