rb25det help!!

[calisfinest240]

Hey guys i've been having trouple with my rb25det neo. Its got a walbro 255 fuel pump and its running on a 92 maxima ecu. For some reason I cant get it to tune correctly and the afr's are all over the place. I had my tuner come over and try to tune it and didn't have any luck. He told me its probably a fuel delivery problem. He said he add so much fuel that the afr's should stay at 10 when boosting at 7psi or higher. For some reason it doesn't do that. On the first pull it will sit at 10afr and then when i bump it up to 10psi it aslo holds at 10afr so, so far so good. Then after a couple more pulls it starts to lean out at 10psi and the afrs start at 10 then spike up to 14. so i put it back down to 7psi and it spikes up to 14 again. So i changed the fuel pressure regulator, and the fuel pump to a new walbro 255 thinking the old one might be going bad. Ran it again and the same situation happens, good for a couple pulls then it starts acting up. Also, when i turn the key in the on possition i cant hear the fuel pump whine like it should. In fact i cant really hear it at all.

If anybody has any feedback on what the problem could be or what i should do next i"d greatly appreciate it. Thanks guys.

[eh?]

Does it do the same thing on the stock ecu?
Sounds like a tuning problem. What does the Coolant temp/fuel trim look like?

[calisfinest240]

I never had the stock ecu from the start the guy that i got the swap from gave me the maxima ecu and tuned it but it was never tuned properly under boost. The coolant temp is fine it never gets any higher. Do you happen to know why i cant really hear my fuel pump turning on? Thank you.

[Zacho]

I've found real Walbro's to be a rather quiet pump.

Whats your fuel pressure like?

The ECU sounds like a questionable issue though. Do you have an RB25 ecu just to test with?

[calisfinest240]

I don't have the stock ecu but i was thinking of getting one. my tuner also said i could ge the z32 ecu and he could tune it. the only reason im questioning the fuel pump is because along time ago it use to whine pretty loud and now i can hear it sputter as its turning on. I cant remember what the fuel pressure was at my mechanic checked it and i think it turned out good, but we werent to sure of what the fuel pressure should be at?

[GSXRJJordan]

Fuel pressure can be set with or without the vacuum line attached, you're looking for ~43psi without the vacuum line attached, and something like ~37psi with the vacuum line attached at idle. That assumes the rest of the car is healthy though.

I think the problem is obvious. You have an ECU in the car that's not stock, you didn't tell us what system you're using to tune the ECU (I'm guessing ROM tune), and you can't get it to run right.

If it were me, I'd find a stock RB25 ECU and try that first.

10:1 AFR is waaaaay rich btw. Tell us what you're using to tune with, what the rest of the motor has (MAF, injectors, FPR, etc).

[calisfinest240]

yes it is a rom tune. the injectors are stock 370's the fpr is from an rb20 and so is the maff. He told me the best thing to do is to do is to tune it with a z32 ecu because it would be way easier. the only thing with that is it don't know if i could directly plug it in?

[eh?]

Is the Maxima ECU tuned or not?

[GSXRJJordan]

yes it is a rom tune. the injectors are stock 370's the fpr is from an rb20 and so is the maff. He told me the best thing to do is to do is to tune it with a z32 ecu because it would be way easier. the only thing with that is it don't know if i could directly plug it in?

If you're using the Maxima ECU I'm thinking you are (for the 93-94, VG30E I believe?) it's exactly the same as a Z32 ECU as far as tunability - same hardware.

RB20 MAF? Sounds like an absolutely horrible idea.

Is the Maxima ECU tuned or not?

It's got to be... this thread would cease to be silly and dive into the realm of truly ridiculous if it wasn't lol.

[calisfinest240]

ya its tuned but it was never ran under boost to see how the tune turned out and now thats what were trying to do.

[eh?]

Did you rewire the Maxima ecu plug into the Neo harness?
I would just get a Z32 ECU & MAF, it should run okay with the stock tune. See if it still happens and if not retune from there.

[HYPNOTIK]

I would start by getting rid of the RB20 MAF. Maybe the ECU is not entering open loop for some reason?

Could the TPS not being calibrated correctly cause the ECU to not see WOT and switch to open loop?