Hello,

I’ve had a misfire/hesitation that seems to have gotten worse ever since I had my motor rebuilt last spring. It’s most pronounced in 5th gear while I’m about 50% throttle coming into 2000 rpm range. The car sputters and misfires. The shop that built the motor has no idea. I had Kenny Dangler from Northern Performance tune the car. I took it back to him to try n diagnose the issue. He couldn’t per se pinpoint to anything either. I’ve attached a couple pics of the data logs where the misfire had happened. Kenny said that the misfire occurred on the right bank where the mv read low, indicating a lean condition at the time of misfire. He also said that the misfire occurred at about the same time the boost started coming on from the procharger. Anyone had any similar issues or experience with understanding the low mv reading?


2016 corvette stingray z51
Built lt1
prc heads
blower cam
D-1sc procharger 3.70 pulley
alky dual nozzle meth injection
motor built by Mullers, package was put together by Texas Speed.
lt 4 injectors and intank fuel pump, dsx low side auxiliary pump.

 

Welcome to the forum. Since it's going lean at the moment you're increasing the amount of air, I would suspect either the injectors or the programming. I don't know if the injectors are controlled individually, by the right or left bank, or all together. That's where I would look myself but then I'm pretty much a four barrel carburetor type of guy. I did have a '65 Rochester mechanical injection on my '73 for about a year. But that's a lot different than electronic fuel injection.

 

I did think potentially a faulty injector. What do you mean by programming? Like tune or?

 

Welcome to the forums. Performance questions are always the hardest. Have you considered contacting HP tuners? I hear they are not the easiest people to contact, its there product you would think they could narrow down the problem. It looks as you have enough graphs to study for your setup. the fact it was acting up before the rebuild it must not be mechanical, you would think. The Injectors could be checked along with spark plugs and even a routine cylinder compression check just to rule out the obvious things.

 

By programming, I meant that if the injectors are controlled individually then that might be a software issue.

 

Thanks for all the help thus far. I may have gotten lucky and figured the issue out. Tho I haven’t driven the car since to tell for certain. I took the car into work tonight to wash and detail it. My co worker had an idea to put a heat gun on all the header runners to see if one cylinder runs cooler than the others to potentially narrow it down. In the process, he noticed a spark jumping from the spark plug wire directly to the header. There also appeared to be a tear in the plug wire insulation. We’ve moved the wire over and it did not spark as the car idled. I also ordered some nice plug wire heat shields. Hopefully this is the end of the dilemma.

 

Hope that's it as that would be an easy fix.