RB25DET S2 WOT Problems

[frankns13]

Hello gents,

Actually posting this for my little brother who just bought a 92' 240 Coupe with an RB25DET Series 2 swap done. It is actually a fairly nicely done swap minus a few wiring mishaps. Anywho, onto our dilemma.

The mods:

-RB25DETS2 swap
-Q45 TB
-Genuine Greddy Intake Manifold
-Z32 MAF (now)
-Empathy (I think is how you spell it?) ECU Tune for the Mods listed above.
-On stock turbo.

The car ran fine for two months after he bought it, then a Couple of days ago he started it up in the morning and made it to the edge of teh development when it started bucking at him. He brought it back home and took it for a drive. I noticed whenever hitting exactly 4500 RPMS it was like a TWO Step rev limiter just bouncing off 4500, would not go past it. I swung back home and opened the hood to find one of the MAF wires disconnected? So I plugged it back in and drove it. This time it would get up to speed if you were not in boost, once entering any boost (even 2-5 PSI) it would Cut out MAF CUT like...) and the RPMS would drop, dead gas pedal, until it idled back out, then the gas pedal came back to life until the next time I hit boost. The guy he bought it from had a brand new Z32 MAF Sitting in the parts box he gave my brother because he said it might be going out, so I put the new one in, nothing changed. I did some searching on various forums for people with similar problems but couldn't find much on it. I heard one person with a skipped tooth on their timing belt so I am ready to dig into that but was curious as to any other suggestions before opening up the timing cover?

Any help is appreciated, sorry if this is vague, i'll answer any questions I can, Nissans are not my fortay, I'm a German Boost nut (N54 335i) but am helping him as much as I can.

[2_Liter_Turbo]

If it runs fine until you hit boost, I'd check for loose intercooler couplers or other sources of boost leaks. Also, check to make sure that the ground wire for the MAF is still connected to engine ground. Z32 Maf's in a 240 swap will have a fourth wire that connects to ground. Another possibility, and this actually happened to me when I had a daughter board setup, was that the daughter board came loose in the ECU. Had pretty much the same issues. So take the ecu cover off and make sure everything is secure. Just be sure to unhook it from the harness and ground your hand on metal before touching anything.

[frankns13]

Looking at the wiring, the person before us wired the signal to the ECU, the 12V to a 12V source from the ECU, and both grounds grounded to the chassis? I assumed the signal ground should go to the ECU but i don't know enough about these swaps? I will check the ECU in a little bit, the FMIC couplers are all new, no vacuum leaks or any other boost leaks That I can find.

[2_Liter_Turbo]

Definitely double check the clamps on those couplers, a somewhat loose clamp can look tight but allow boost to spill out under load. It has happened to me in the past when I forgot to tighten a clamp, ha ha.

You are supposed to wire one ground to the factory ground lead that grounds into the ECU and the other to engine ground. I suppose in theory, that having both to engine ground would do the same thing, but I like to keep everything as OEM as possible. Don't want to add any ground loops or anything.

[frankns13]

Oh I am very familiar with Boost leaks... (stupid BMW plastic charge pipes ). I will check he couplers tonight as my brother is the one that put those on lol. I will seperate the grounds tonight as well.

[2_Liter_Turbo]

Oh I am very familiar with Boost leaks... (stupid BMW plastic charge pipes ). I will check he couplers tonight as my brother is the one that put those on lol. I will seperate the grounds tonight as well.

The ground wire next to the 0-5v signal wire needs to go to engine ground. The one next to the 12V source, needs to go to the ecu. Just so it's like factory (info from Z32 factory service manual). I just did this on my Infiniti G20, hence the memory, ha ha.

[240Robby]

Sorry For Posting A Question On Your Post, Just Joined And Don't Know Where To Start One. I Recently Bought A RB25DET Powered 95 240, It Ran Fine For 3 Days Then Just Shut Off. It Had No Issues Only Has 70K And Its Also No Getting Any Spark Whatsoever Could It Be A Cam Angle Sensor And If So How Can I Fix It Please!

[frankns13]

Checked the daughter board, and it seems to check out okay. Replaced the clamps needed, and tightened everything down after checking them all, and still no change. Car will still drive as before, but the same type of dead-pedle at boost is still there. Even without hitting any level of boost, the car as if cuts out, but it's very faint. Once hitting boost (even 1-2psi) it just throws itself into a constant cut-out of power and all pedle control is lost until it either settles itself or I just let off the pedal completely. Checked the TPS as well as another buddy of mine had suggested it, but nothing is wrong or out of place with it. Any other suggestions?

[2_Liter_Turbo]

Did you check the plug gap?

[frankns13]

Replaced all plug with now a .8 gap. I can't remember what the exact name of the plugs were, but I can get them tomorrow. The hesitation and as if dead-peddle is still there. The car drives MUCH better overall, but it didn't solve the issue. The car starts, drives, and overall runs better now, and I can somewhat hold a steady amount of gas with less of a break-up, but yet again once I hit any form of boost, it will start to break-up and die out.

[2_Liter_Turbo]

I wonder if you have bad coils or something. Like the spark energy isn't very good so anytime you hit boost, it blows it out. New plugs helped, but if the coils are not up to par, then you won't be able to push it at all. Know anyone with the same motor you can borrow coils from?

[frankns13]

Not off the top of my head. I'm new to the area I live in, so I don't know anyone around here really. I'll try posting on a few local pages real quick to see if anyone would mind helping me out.

[2_Liter_Turbo]

Not off the top of my head. I'm new to the area I live in, so I don't know anyone around here really. I'll try posting on a few local pages real quick to see if anyone would mind helping me out.

Also keep in mind the ignitor chip. I honestly don't know which cars cross-over, but you could try the wrecking yard for quick cheap parts. Just look out for Nissan/Infiniti cars with distributor-less ignition (some maximas, Q45, etc). Keep us posted!

[Wiring Specialties]

Frank, if you are still having some issues with the wiring job that the previous owner did, we have a plug and play harness that will replace everything. Startup guaranteed.

If you are interested, you can check it out here: http://www.wiringspecialties.com/wsprrbs1ands.html