Rb25det Misfire/acceleration Issues (common Problem)

[Michaelove]

The car is a 1995 240sx with an RB25DET and we're having some problems with it, it's a common problem we're experiencing with some weird quirks.

The Car

RB25DET

Stock ECU (for the RB25, not a 240 ECU)

Rebuilt t3/t4 turbo

Greddy Front mount with custom piping

Apexi n1 BOV

Blitz cold Air intake

Blitz NUR spec exhaust

Custom down pipe

Custom test pipe

Walbro 255 Fuel Pump

HKS electronic boost controller

Apexi Air Fuel Controller

The problem

Stuttering/misfire/hesitation above 4500RPM under full throttle. Previously the car had major problems ever getting above 5000RPM, so we started diagnosing and hunting down known problem spots and eliminating them in order to try to fix this.

Previous Attempts to Fix the Problem

Replaced Spark Plugs

Clean & Silicone the coil packs

Upgraded fuel pump

Cleaned the ICV

Did minor tidy/restoration work all across the engine bay

Reset the ECU

Repaired many vacuum leaks

Responses

We tested the coil packs just recently, all of them were between 1.1 and 1.2 ohms, we put silicone all over the coil packs to prevent arcing, and it alleviated the problem some but the car is still not perfectly driveable.

Under full throttle in any gear, upon hitting 4500RPM, the car hesitates/misfire/etc. So we decided to play around a bit, we know that if we slowly work our way up to the higher RPM's at half throttle, we can hit 5000, and if we go full throttle AFTER 5000, the car will hit 7000RPM with a small amount of misfire but it's MUCH better. In third gear, there are some problems after 5000RPM but nothing major compared to before, where it would not accelerate past 5k under full throttle at all.

What do you recommend the next course of action is, currently we're getting a PowerFC and a tune next week but if there's something we need to do before that will not be fixed by the PowerFC/Tune, we need to know before we make arrangements, is this problem easily alleviated by something simple? Should the fix be done BEFORE the tune? Or can the fix be done after the tune?

We have searched but haven't found something like this, there have been similar threads but maybe someone can offer some more insight.

[bluey33]

We have searche but haven't found something like this, there have been similar threads but maybe someone can offer some more insight.

Plenty of these these threads. PLENTY.

Anyhow your standard ECU is hittin R&R. Seeing as though you are gettin PowerFC and tune next week, then there should be no problem. The FC will fix it up

[Michaelove]

Plenty of these these threads. PLENTY.

Anyhow your standard ECU is hittin R&R. Seeing as though you are gettin PowerFC and tune next week, then there should be no problem. The FC will fix it up

Will installing new coil packs after the FC install/tune affect the FC negatively?

[Guilt-Toy]

You probly dont need coilpacks.. the standard nissan ones are better then all the aftermarket ones its just when they get old they can start to arc out.

Dont buy them if you dont need them, i made 363rwkw from stock coil packs.. but they were low km ones i scored

Will installing new coil packs after the FC install/tune affect the FC negatively?

[DECIM8]

Your sparks are gapped at 0.8 or lower right?

[Michaelove]

Your sparks are gapped at 0.8 or lower right?

Yeah they're at 0.8, and also the resistance seems kinda high - 0.9 ohms seems to be the highest we should go, is it bad that we're getting readouts of 1.1 to 1.2 across all 6?