Last week my Z28 developed a misfire problem. On the way home from Danville, VA it started to surge under load in 6th gear. It's now felt in 2nd-6th under even light load. The car is way down on power.

I recently discovered this gentleman's youtube channel.

www.youtube.com/user/ScannerDanner

He has some damn good information on how to troubleshoot misfires, injector issues, and many other things. He shows how to do it with a o-scope and explains the various waveforms. Very good information. Anyone interested in automotive troubleshooting should check out his videos.

I've spent most of the day looking at my issue. I recently purchased an old Fluke 96B series II scopemeter off ebay and have been using it to look at the injectors, MAF, fuel pressure, and the ignition system. Fuel pressure is fine as are the fuel injector waveforms.

I've had trouble not being able to use the x10000 probe for the ignition system(got this off ebay too..must have as not to destroy the o-scope when trying to observe secondary ignition). It clamps around the plug wire and does not seem to work well. I'm not sure if the wires are shielded so good that the probe will not work...or if it's just bad. I may have to put money into what Dan has in his videos, but I think I've found my problem without it.

The car did not throw any misfire codes at all. That got me to thinking.....if you have an aftermarket cam installed, chances are pretty good that when you got the PCM programmed, that P300 was disabled. That was the case with my PCM. A couple of years ago, I re-enabled it and every couple of days of driving the car, it would flag a random misfire code. Nothing major, that I can recall...just a few misfires. The car ran perfectly fine....so to keep from seeing a false misfire(from a different cam), I disabled the code as was from PCMforless(as a side note, I used JetDST for this).

So, today, I re-enabled it to see if it was preventing the PCM from picking up my trouble. Sure enough, I didn't get 200' from the driveway when the PCM lit up the SES light like a Christmas tree. All kinds of blinking and the misfire counters started working overtime. It pointed to 8 and 4 having 1600 and 600 misfires respectively. All the other cylinders were around 20-40(used Autotap with GM enhanced parameters to scan the car). So be aware, that on an OBDII car, turning back on the P300 code can allow the PCM to help you with misfire issues.

As it got dark, I turned off all the lights in the garage and I think I've found the problem. The ignition coil and plug wires.

I've been changing plugs out left and right trying different things at the track and must have made the plug connectors too loose. I can see a blue glow around the boots on 1, 6, 2, and it's really bright blue on 8. I can also see sparking going on around the ignition coil. There are all kinds of nice blue hues around the ignition coil core and coil windings.

My coil and ICM are both 16 years old. I went ahead and ordered a coil, ICM, and wires(all AC Delco). I've also decided to go back to AC Delco wires. The Moroso 7.5mm wires are fine, but they are absolutely hateful to snap onto a plug. The boots around the plug are so tight that it's extremely hard to be sure the wires are on the plugs. I never recall having that issue with the Delco wires.

Hopefully, this will fix my misfires....the only thing that worries me is that the wires would fire an ST-125 plug tester(at least on 1, 3, 5, and 7.). Since the passeger's side is the most difficult to reach, I have not tested them, but the PCM is pointing to 4 and 8 having the most problems. So we will see.

 

With the buttons for 8 and 4 right next to each other in the Opti cap, you may have some carbon tracking causing them to misfire.

I wish I had the in-depth electrical knowledge to approch the problem like you did.

 

That's an excellent observation. The opti being the problem is still a real possibility. I'm hoping it's not as it only has around 7000 miles on it. The ignition probe not working has put a real damper on the approach I wanted to take on it.

In Dan's youtube channel, he goes through what the various waveforms should look like and what some will look like given certain types of failures. He has really helped me get a handle on what to look for, but I'm going to have to find out why the ignition probe didn't work or get another one(or type).

I can say this about the problem....it went from running fine to misfiring badly in the course of a hour. To me, that would point to some type of electrical failure since there is no mechanical noise as to a failure(ICM and Opti were on my mind). I've pulled the valve cover for the driver's side and all looks good. I'll pull the passenger side when I do the plug wires. I didn't think that the plug wires or coil were to blame, but as they are glowing at night(with 8 being the brightest) I'm going after them first. Not to mention that I hate the current plug wires, seems like a good reason to change them. However, the opti still looms large.

 

Have a look at this video....starting at the 6 min mark. He goes through the setup before that mark.

[autostream]http://autostream.com/camaroz28/?page_type=firebirdplayerthumbnail&framepage=2724& transactionid=1350859421-75191131167&posted_by=ACE1252_www.camaroz28.com&yo utube_video_id=XfOkTAJOi74[/autostream]

I was trying to look at this on my scope. No dice with my ignition probe, but if something is going on with the opti secondary side, I would expect to some type of abnormal pattern.

 

I'm awesome like that!
[EDIT] hidden spam links deleted

 

And.... your IP address is in China, and you have buried Spam links in your post.

Hasta la vista, baby!

 

LoL I'll update after I get the new parts on the car this week.

 

Well, I replaced all the plug wires, ICM, ignition coil, #4 plug and #8 plug. I just got back from the test drive. The skip is gone and all the power seems to be back. It was blowing the tires off in first at 4000rpm. Lugging it in 4th, 5th, and 6th resulted in smooth steady acceleration....no skipping. It seems to be fixed.

However I'm surprised. I didn't really find anything wrong with the #4 and #8 wires and the plugs didn't look bad. I wonder if the ignition coil and ICM had more to do with it than I thought. Still the car sounds a little different than it normally does.....maybe a little stronger sounding.....I'm not sure but it's not quite the same as before which in itself worries me a little. If that dang ignition probe worked I could look at the difference on the scope.

I hope it's not a case were the new ignition coil is developing enough voltage to overcome a possible carbon tracking problem in the opti at 4 and 8(covering it up to come back later), but I'll just have to drive it a few days and see what happens.

I may even take it to the track this Friday to see what it runs.....see if it's lost or gained power.