Cylinder #6 Misfire

[hermes]

It started when I replaced the stock coil packs with Accel packs from Summit.
About a week later, the ECM threw a P0306 DTC - #6 cylinder misfire.
I checked the plug wire at both ends and they were okay.
I moved the coil pack that controlled #6 and the misfire moved to #2 cylinder – bad coil pack. Called Summit, they sent me a new one,problem solved. For about 4 days.
Threw another P0306 DTC.
Checked plug wires, connected okay. Moved coil pack, no change.
Checked impedance on #6 plug wire, open gap.
Replaced plugs and wires (#6 plug had some build-up on theceramic) with Accel 8mm and NGK Iridiums.
No change.
Replaced Ignition Control Module.
No change.
Checked compression – 185 psi on #6, 168 psi on #4, 150 psi on #2 - less than 20% difference across the bank. Acceptable.
Swapped fuel injector #6 with #2.
No change.
Checked MAF sensor by unplugging with engine running.
No change.
My next step is to change the upstream O2 sensors.
If there is no change, I will check for an obstructed cat. I have not noticed a change in exhaust tone, but I am not the primary driver.

About 3 months ago. I replaced the fuel pump and filter.

Hermes has about 105,000 miles behind him and is driven approximately 20 miles each way to work 3 days a week and 2 miles each way the other 2 days.
About 1 week before, we returned from a road trip to Michigan with an occasional hic on the road, but nothing this bad. The hiccup was similar to the symptom 3 years ago when I needed to replace one of the coil packs, thus prompting me to buy the Accel units (if you have to replace them anyway...)

I'm not sure where to look next.
Any input would be appreciated.

Thanks in advance.
Dave

[Cammy98]

Re: Cylinder #6 Misfire

Have you put back the old coil packs and see what happens?

[ssms5411]

Re: Cylinder #6 Misfire

X2 I would use the stock coil packs they seem to last the longest and work the best. I have never had anytrouble to the stock coil packs on my car and itgets to 115+ here in AZ which heat is a killer on stuff like that.

[hermes]

Re: Cylinder #6 Misfire

While I was waiting for the replacement from Summit, I had one of the old coil packs in place and still had the #6 misfire. And it wasn't the coil that previously controlled #6, so I'm not sure that's the problem.
I've got the new O2 sensors. Right now, the bungs are soaking in PB Blaster, waiting to loosen up.
BTW, The O2 sensors for the '97 Firebird could be one of two connector styles. The early '97 (at least this one, which was built in August '96) has a square connector like the '96s. The later '97 (which is what is listed as "direct fit") has a flat connector.
I'm not sure what the actual cutoff month is, but you may want to check your connector before you go to the parts store. Of course, the square connector is about $17 more than the flat one.
FWIW
Dave

[hermes]

Re: Cylinder #6 Misfire

Update:
Changed out the upstream O2 sensors.
Check cat flow. Adequate
Cam position sensor changed.
No change.

This is starting to get frustrating. Haven't had Hermes on the road in a month.
Looks like I may have to have him towed to the dealer for a diagnostic to see what's wrong.

[ssms5411]

Re: Cylinder #6 Misfire

I would be checking your wires maybe move #4 to #6 just to make sure and put the stock coils back in, also make sure your injector plug is all the way on and OHM test them to see if it has gone bad, I've had that happen before took me a year to find out what injector was bad since it just through a PO300 which could of ment alot of thing but it was a bad injector. I have had the #6 plug for the injector come loose also just bumping it when cheking the map sensor back there and also a pintch wire or brken wire on the injector harness. So there is a few more things you can check instead of paying $90 a hour at the dealer who will just keep on replacing stuff so they can get mre money out of ya. Good luck finding it and try some of the stuff I memtioned it will eliminated alot of other stuff.

[3.4grapeofwrath]

Re: Cylinder #6 Misfire

What does the spark plug look like in cyl. 6? If it is fouled with carbon it is probally an ignition problem. If it's white it's probally not getting fuel.
I wouldn't be replacing parts that would effect all cylinders. O2 sensors,cat,
cam sensor etc would cause problems for more then one cylinder. Concentrate just on cylinder 6. It could be a mechanical problem also.
Worn cam lube, lifter or even a broken valve spring.

[hermes]

Re: Cylinder #6 Misfire

Update:

After deciding that I would give in an get a dealer diagnostic to find the problem (I don't have a problem paying a diagnostic fee and fixing it myself), I decided, WTH, I'll give the ECU a reboot (disconnect the negative lead) and move the trouble coil again, just to make sure it's not the coil.
After reconnecting the battery, the misfire moved!
Okay, bad coil. Made a call to Summit for a replacement (still under 90 days since the last one was sent) and they sent me a new one.
Hermes runs fine now.
I feel kind of annoyed, since I had done the same thing before with no results,but the problem has been solved and Hermes needed his 100k maintenance anyway.
Thanks for all the help guys.
Dave

[ssms5411]

Re: Cylinder #6 Misfire

I would still go with stock coils an just return the Summit ones.