RB25 intermittent cuttout issue. - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Guilty1s · 07-11-2014, 09:11 AM

Series 2 rb25
-stock ecu
-fresh stock motor
-3" FMIC
-Freddy IM
-vented Bov, I know but it's not the issue
-running wastegate pressure
-zero boost leaks

New motor to us. Drove it around for a couple day fine. Pulls real hard. Then it will start hesitating. Pretty much fuel cut as far as I can tell. May be spark cut but I don't think so, wideband read lean during the cut. What is making it so hard to diagnose is that it is intermittent. Turn the car off. Turn it back on, it is fixed, pulls like a champ. It may last 10 seconds, it may last 10minutes. At stand still, when the issue is present, won't rev past 2000 something rpms.

My first assumption was MAF, it fits.Have put 4 other e60 mafs on there and act the same situation. I checked all the wiring and it checks out fine but it is hard to be 100% since it is an intermittent issue.

I am using ecutalk and everything looks fine.
-coolant temp in check
-cycling o2 sensor
-perfect tps
-base timing as expected
-maf reading as expected but it does hit 5v on a WOT pull. I didn't think a stock rb could do that at 9-10? Psi. The butt dyno tells me only about 260hp maybe?

Here is where I find it gets interesting.

I put a new ecu in it. Boom. Fixes it. Swap back to the old one immediately to make sure it's not a fluke, runs like shit again. Put the new ecu back in. Run good, Like 2 small burps for a split second in about 2 days running perfect otherwise. Then the same exact issue comes back.

That's where we are at today where we swapped the old ecu in today and it runs fine for now, but we expect it to start it's intermittent problem again...

Any ideas?
Learning LT or ST fuel trims odd or something?

Sent from my iPhone using Tapatalk

TwoForDeh · 07-15-2014, 06:39 AM

Did you break open the other ecu to check for burnt pins or anything? I had this same issue a while back with my RB. The kid that wired it up left a bunch of open connections and shorted out the ECU. It ran great, then it all went to shit. Then would be ok for a few. Then go back to shit. I pulled the harness, rewired it, put a new ecu in, and it's been good ever since.

tom_sr20 · 08-01-2014, 06:44 AM

my engine is doing the exact same thing. mine is an sr20 though. i never found a solution for it. its been a year of trying. hesitation begins after mins of driving, shut it off and normal again on restart. pls let me know once u fix this. the only thing i haven't change is the hacked out wiring harness.

Guilty1s · 08-10-2014, 06:08 PM

3rd ecu... Same thing

Rewired the maf from ecu to maf with shielded wire... Same thing.

07-11-2014, 09:11 AM	#1
Guilty1s Zilvia Member Join Date: Sep 2011 Location: Knoxville, TN Age: 33 Posts: 263 Trader Rating: (1) Feedback Score: 1 reviews	RB25 intermittent cuttout issue. Series 2 rb25 -stock ecu -fresh stock motor -3" FMIC -Freddy IM -vented Bov, I know but it's not the issue -running wastegate pressure -zero boost leaks New motor to us. Drove it around for a couple day fine. Pulls real hard. Then it will start hesitating. Pretty much fuel cut as far as I can tell. May be spark cut but I don't think so, wideband read lean during the cut. What is making it so hard to diagnose is that it is intermittent. Turn the car off. Turn it back on, it is fixed, pulls like a champ. It may last 10 seconds, it may last 10minutes. At stand still, when the issue is present, won't rev past 2000 something rpms. My first assumption was MAF, it fits.Have put 4 other e60 mafs on there and act the same situation. I checked all the wiring and it checks out fine but it is hard to be 100% since it is an intermittent issue. I am using ecutalk and everything looks fine. -coolant temp in check -cycling o2 sensor -perfect tps -base timing as expected -maf reading as expected but it does hit 5v on a WOT pull. I didn't think a stock rb could do that at 9-10? Psi. The butt dyno tells me only about 260hp maybe? Here is where I find it gets interesting. I put a new ecu in it. Boom. Fixes it. Swap back to the old one immediately to make sure it's not a fluke, runs like shit again. Put the new ecu back in. Run good, Like 2 small burps for a split second in about 2 days running perfect otherwise. Then the same exact issue comes back. That's where we are at today where we swapped the old ecu in today and it runs fine for now, but we expect it to start it's intermittent problem again... Any ideas? Learning LT or ST fuel trims odd or something? Sent from my iPhone using Tapatalk

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07-15-2014, 06:39 AM	#2
TwoForDeh Zilvia Junkie Join Date: Feb 2013 Location: NH Posts: 426 Trader Rating: (0) Feedback Score: 0 reviews	Did you break open the other ecu to check for burnt pins or anything? I had this same issue a while back with my RB. The kid that wired it up left a bunch of open connections and shorted out the ECU. It ran great, then it all went to shit. Then would be ok for a few. Then go back to shit. I pulled the harness, rewired it, put a new ecu in, and it's been good ever since.

08-01-2014, 06:44 AM	#3
tom_sr20 Join Date: Apr 2012 Location: Guam Posts: 33 Trader Rating: (0) Feedback Score: 0 reviews	my engine is doing the exact same thing. mine is an sr20 though. i never found a solution for it. its been a year of trying. hesitation begins after mins of driving, shut it off and normal again on restart. pls let me know once u fix this. the only thing i haven't change is the hacked out wiring harness.

08-10-2014, 06:08 PM	#4
Guilty1s Zilvia Member Join Date: Sep 2011 Location: Knoxville, TN Age: 33 Posts: 263 Trader Rating: (1) Feedback Score: 1 reviews	3rd ecu... Same thing Rewired the maf from ecu to maf with shielded wire... Same thing.