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While my car was on the dyno two times now it has been misfiring at 5500-5700 rpms. Any advice on where to start troubleshooting? Since this is happening on the dyno they are able to see it. How would I be able to see this on the road? What software are you guys using to log these cars? It's a 97 Z28.
It currently has a dynaspark on it. Do you think that is still the problem? Just got the car back in the garage so I'm going to start troubleshooting soon hopefully. Any ideas how I can monitor to see if I still have the misfire?
Most likely the optical sensor on the opti is going bad. I chased a high rpm misfire for months denying mine was bad. Changed cap/rotor with the same result. Changed out opti for a new one and it magically went away.
Problem is, who now manufactures one that is dependable?
It currently has a dynaspark on it. Do you think that is still the problem? Any ideas how I can monitor to see if I still have the misfire?
dynaspark Opti's are not immune to fail. IDK if they are still in biz or not. High RPM miss is often associated with optical sensor (in opti) failing. Yeah it could be something else in ignition...but Opti is most likely suspect. You need a oscilloscope to see low & high resolution operation of Opti. Scan software can show misfires, Failing Opti typically does not throw a code.
Opti's available today are a crap shoot. AC Delco remanufactured ones seem to be the "better" of them but are very hard to find. Occasionally rockauto.com has them.
This source came up on another forum as a place to "rebuild" the Opti but I believe it needs original AC Delco ones with the Mitsubishi sensors in them to rebuild. He may have donor ones to sell, worth checking out. II have no direct experience with them
I believe the dynaspark was from 2009-2010. I wasn't saying it is bullet proof but have heard great things. I'm going to test the wires and check the plugs but just a gut feeling it is the Opti.. I don't really want to replace it with another one. What kind of plugs do you guys use and what do you gap them at?
[QUOTE=z28jimmy;19908507 What kind of plugs do you guys use and what do you gap them at?[/QUOTE]
Per the tuner I use, Ed Wright, I use Autolite 106 at .050 gap. I noticed the porcelain is slightly thicker than the NGK and the plug is slightly longer also (pic). I have headers and Autolites are not a fit problem
Ed said when he had his dyno shop he had a bucket full of NGK's next to his computer he pulled on cars he was tuning. Said high RPM miss was why (not the only reason that can cause one though). Said not only could he see the misfire on dyno graph at high RPM, you could hear it out exhaust if standing behind the car during a pull.
Given Ed has forgotten more than I know about LT1 and tuning...I take his advice
Per the tuner I use, Ed Wright, I use Autolite 106 at .050 gap. I noticed the porcelain is slightly thicker than the NGK and the plug is slightly longer also (pic). I have headers and Autolites are not a fit problem
Ed said when he had his dyno shop he had a bucket full of NGK's next to his computer he pulled on cars he was tuning. Said high RPM miss was why (not the only reason that can cause one though). Said not only could he see the misfire on dyno graph at high RPM, you could hear it out exhaust if standing behind the car during a pull.
Given Ed has forgotten more than I know about LT1 and tuning...I take his advice
04-07-2018, 07:20 PM
Mis fire at 5500-5700 RPMs 
