1JZ RPM breaking up at 3500ish, Sounds like spark cut rev limiter almost

[Devin LeBlanc]

Just did a 1jz swap for a customer. Along with the full wiring. It has new spark plugs gaped correctly. There is no misfire under normal driving. It has a Walbro 255 fuel pump with a 12 gauge wire and 30 amp relay circut wired to it. I have logged voltage while under load and also fuel pressure and is holding great. No check engine codes either.

Here are a few videos. Im pressure sure it is an ECU problem.

[video=youtube;OxlOHdTLVas]http://www.youtube.com/watch?v=OxlOHdTLVas[/video]

[video=youtube;Ke_f_yaQprs]http://www.youtube.com/watch?v=Ke_f_yaQprs[/video]

Thanks,
Devin LeBlanc

 

[hvyman]

Cracks on coil packs?

 

[suprahero]

Unless they're cracked completely open EVERYWHERE I doubt it will be the coil packs. I know they cause break ups, but it's usually under boost and higher in the rpm range.........or at least mine did.
Have you tried a different ECU to see if it could be bad?

 

[IBoughtASupra]

How is your fuel rail being fed? Stock banjo line or DM feed line?

 

[Devin LeBlanc]

Its a Stock Banjo line, It is all stock other than exhaust and intake. I do not have another ECU to try

 

[hvyman]

Open it up and see if the capcitors are leaking.

 

[Devin LeBlanc]

Have already checked, It all looks pretty good.. Maybe one little trail out of 1 cap.. Which could definitely be causing it. Nobody else has seen this before?

 

[hvyman]

If its leaking its leaking. Shouldnt have any leakage. The more it leaks the worse it gets as well.

 

[mjsn1]

I had a similar thing. when i was cleaning the car some water leaked into the ECU and it did just that. so the problem is definitely from the ECU.

 

[*james*]

I have the same problem, just replaced my cracked coil packs with crackless coils and it didn't fix the problem.

Leaning towards the fuel pump now, as far as I know its the original. Checked the ecu before I got the motor running, it was fine, I guess I should probably double check it.

 

[S.A. supra]

Could be the coil packs it happen to me.

 

[Chrisco]

Devin, did you ever determine the root cause of this problem? I believe my 7MGTE powered car is having a very similar issue. Details can be found here:

http://www.supramania.com/forums/sh...egardless-of-Load-Boost&p=1827123#post1827123

 

[Devin LeBlanc]

It was the crank position sensor trigger wheel causing the problem. Doubt it would do it on a 7M. More thinking spark blow out if its with a 7M