For some reason my car has been breaking up above 6K. If I run the stock tune I can go out to 7K no problem! The AFR doesn't dip, it shows 0 KR and 0 misfires!! It's extremely strange!!

I sent Bill from HPT my log of it as well as Vince with a log using his logger. Everything looks fine, you can't see it doing anything wrong looking at a log. It def has a misfiring sound and the car noses over too!

I changed spark plugs, tried different gaps and even tried a new Front O2 again for the hell of it. Im at a loss. The only thing I can think of now is a coil pack or injector but the car is as strong as ever below 6k. It doesn't smoke AT ALL and I did a Comp & Leakdown test on the car, solid 155-160 across the board!


Any ideas anyone??

 

Map sensor

 

my lsj did this when it **** an injector

 

I was having a similar problem around 6500rpm but Vince was able to see an issue with COT and got it straightened out...

Good luck Nick!

 

bigger gauge wires for injectors..??
it's almost like a progressive deterioration as it gets hotter they don't conduct as well

 

with my gli I had a misfire problem but only in the high rpms and it turned out to be a coilpack.

 

My SS/SC just did something like this yesterday morning. I got on it when I was pulling onto the highway, and it felt like it hit a wall around 7,000 rpm (my limiter is 7,250 rpm). My shift light on my interceptor is set at 7025 rpm, so I knew it was before that and my limiter. I took it out later that afternoon, and did a pull. Pulled all the way to 7,250 rpm without issue. Zero missfires, and zero knock. If it happens again I will look into it more.

 

i had tht problem with an lsj and it turned out being the boost over 6k was limited to stock settings.

 

They seem to be reading fine.

Yea, that's what Im leaning towards. Its just weird that it only does it above 6k and only when making more load then the stock tune

 

im going to go with a coil pack as well. this happened to me a year or two ago. granted i didnt have DI but i dont think it should matter.

i dont think thats weird at all. its not maxxed when its on stock tune i dont think

 

I'm guessing your tune modified fuelling over the stock tune up top to reduce the drop-off? If so that's one delta right there that might explain it. If you haven't then it's definitely a head scratcher.

 

Byt,

What valve springs are you running? I am wondering if you are getting some valve float and/or coil bind due to the extra stress from the tune. I am also wondering if you are starting to have a problem with a lifter, as they are a hydraulic type.

I have seen this on hydraulic cammed SBC and BBC. Most of them would not rev past 6k without problems, that is why I went with a solid cam.

Another thing with my old car, when I would try to rev over 6k with the old fuel pump, it would pop and make some not so happy noises. Do any of the logged tables show that you might be going lean at the high end?

 

Wont be the springs, he said he can put the stock tune in and raise the limiter to 7000 and its fine. Kind of makes me think injector, only because with it running stock tune to 7k its fine. But with the added fuel the injector or injectors cant keep up with the demand. I also wonder, what about the fuel pump? I had that same kind of stuff happen with my truck, would sputter and die off in the higher rpms.

 

not necessarily, stock tune is a lot less boost, less fuel and less timing, totally possible to have valve float and only be noticed at high RPMs on a tune. Remember, a tune enhances the effect of ALL malfunctions. Could even be things like a worn turbocharger (shaft end play) which normally have little effect until they are bumped beyond factory specification. I DO NOT suspect injectors, the problem would present itself at lower RPMs with high load conditions as well, stock or not.

Also, these valve springs aren't particularly awesome by any stretch and fatigue happens.

 

It almost sounds like spark blowout. I had this happen to my old LSJ when i was messing with Gap's . I know you already mentioned it but it described what I had experienced to a T.