The reason I ask is that I've been fighting a P0300 - Random Misfire Detected code. I've changed the spark plug wires and even hooked up my Diablo tuner and determined that it was cylinder #7 and sure enough when I took the wire off of the plug nothing. So I just got back from the parts store and put on a new coil-pack for cylinder #7. Maybe it is just me but I think it made the problem better but it is definetly still there but I can't really tell from the idle, or driving it but it says it is misfiring and the tuner says it is misfiring. So what comes before the coil-pack? Where should I start checking?
-David

This is the link to the other thread I started about the P0300 code -> Click

Also I did just install headers. But I don't see any loose wires or anything and I checked over my install pretty good but maybe I missed something. Any ideas?

 

I don't know how well the Diablo Tuner works or what functions it can perform but I would get access to a real scanner.

Have you checked for a cracked spark plug since you recently installed the headers. It will be a fine crack along the porclene.

If you can get a Tech 2 or any such scanner it would help narrow down the cause.

You can observe individual cyl misfires, bank to bank leak conditions, and do a cyl balance test.

The ignition system itself is a good system. The coils have power during Key On/Run and the PCM supplies ground to trigger the coils.

The Simplistic Answer
The PCM gets a signal from the Crank Sensor (CKP) and the Cam Sensor (CMP) to determine RPM and which cylinder it is on. The PCM crunches the numbers based on the parameters built into the software and other inputs . It then grounds the coil to cause spark.

The in-cylinder explosion causes a smile on the face and it all starts over again.

 

Try switching coil packs, its very easy and will at least rule out a bad coil. If you have removed the plug wire and it is not firing, ie... you put a tester in there or a screw driver and grounded it to look for spark, then I'd look to see if there is a signal going to the coil. Then, just work backwards. I doubt its going to be the mechanical pickups, would be unlikely for it to cause one cly to not fire. Not impossible, but unlikely.

I'm not sure of your mechanical prowess so go with caution. If you don't know what you are doing then seek help. Not trying to be offensive, I just don't want to suggest you test stuff and have you fry something and get mad at me. Let us know what you find and we will go further, but let us know if a known good coil fires there, if not do you have a signal to the coil etc...

You said there was nothing at the wire. Remember it needs ground to fire or spark. You need to get the wire close to a ground to see the arc jump. I usually use a tester or a small screwdriver inserted in the boot and making good contact with the metal end. Then hold it close to, but not touching a good ground source. Sorry for the dumb statements but its tough to know the level of the poster.

Its very easy to crack a plug druing header install. Put a known good plug in the suspect wire, ground the thread portion and see if it fires.

Let us know.

On a side note, did you ever own a red 911? I used to talk to a guy that had one with the same plate as yours.

 

I'll double check the plug for cracks and I don't have an actual scanner but I was able to monitor misfires with the diablo tuner which said it was cylinder #7. I'll try to find an actual scanner and see what I can do.

I already bought a new coil so I doubt I got a bad new one but I'll double check it all.

I'm not exactly ASE certified but I do have some knowledge of what is going on. I just need an outsiders opinion cause I'm pretty stumped at this point. I'll double check for an arch maybe it wasn't close enough to arch. I'll let you guys know.

Edit: absolutely no arch. I think I have a meter I just have to find it and I'll let you know if I can determine if the coil pack is getting any power.

Any change I pulled a wire loose for just that coil. I know there is a harness on the top of the coilpack which is on there but I can't imagine what else it would be..

And no lol it wasn't me with the red 911

 

Trace the wiring from the coil pack harness back and look for damage. Sounds like you're not getting power to the coil.
Good Luck.

 

Problem solved it was a loose wire on the coil harness.

Can't believe how easy it was.

All thanks goes to HawaiiC6 he solved it. Thankyou again.