Rb25det Performance Issues

[Fox - R32]

G'day,

I own an R32 GTS-T with an RB25DET conversion. Recently it was having a bit of trouble, as soon as it would start to boost or put down any sort of power it would just jolt around and backfire a bit and then take off. I took it to a tune up shop who dynoed it and ran every check they could think of, which resulted in a new MAF and fuel pump, which made it better but not great. It will now put down a bit of power but as soon as it gets up to around the 5000-6500rpm range it misfires and sounds unhealthy. The mechanic said the only thing left he could think of was a computer problem, and i was just curious if anyone else has had this issue. I will buy a new computer if needs be or is there anyway of checking to see if the computer is reading healthy? Apparently it is a bitch of a car too seeing as the engine conversion has left it with unused wires here and there and parts running to different places and what not.

Also i just bought a new water temp gauge to go on my pillar, and i was just curious what is the easiest way to put it in without messing up my thermostat or my ecu, and preferably without removing or messing with the gauge already in the dash. does anyone know the location of the dash probe on the cooling system?

Any help would be greatly appreciated.

~Chris

[ClutchBurndout-:(]

straight away it sounds like a mixture problem, checked ur plugs? injectors? maybe run an injector cleaner through? it sounds like, not enough fuel can spit out at higher rmp, have you adjusted boost?

[Fox - R32]

straight away it sounds like a mixture problem, checked ur plugs? injectors? maybe run an injector cleaner through? it sounds like, not enough fuel can spit out at higher rmp, have you adjusted boost?

Yes, yes and yes. The mechanic said it might be an injector, but it wouldnt explain why sometimes it does it and very rarely it doesnt and that you would feel it all the way through the rev range. He reckons he checked everything, plugs, coil packs, fuel pressure, fuel flow, turbo, compression and all that and fixed a few faults but it didnt appear to help. I turned my boost down to about 8 pounds and it alleviated the problem a bit, but yeah, still not going good. He also said when he raided the fuel pressure up to around 50 pounds the car was running perfectly but he said something about not being able to keep it at that, i dont know why... would a computer related problem be at all possible or do you reckon i should get a second opinion in a different garage?

[PHT33]

Coil packs...are they the stockers? Have you gapped the plugs down to .8, even .7? Have you got 5's or 6's (heat range of plugs)? Also check the wiring loom for the coils and see if it looks dodgy like burnt wiring or cracked plugs.

[eeiko321]

i should get a second opinion in a different garage?

what state are you in?

well put it this way

Injectors can be tested with a multi meter......

if your interested PM me and ill explain to you how..

other wise......... YES........ that mechanic sounds like a dead-beat...

which workshop is it by the way? its interesting to know this..and may warn other people.......(or maybe even other people have run-ins with him)

but id say take it to someone more reputable...

coz i think hes either taking you for a ride.....or hes just replacing things by guessing...........

thats not the way to do it

[Fox - R32]

I am not sure about the coil packs, i believe they would be stick, they were all working correctly apparently. And i am not sure on the spacing of my plugs but apparently there were a couple spaced differently when i dropped it in but they have all been adjusted. I live in north west WA so yeah, there arent any japanese specialists up here lol. I know the mechanic and i know he has worked on several skylines and GTRs and supras before and he seems to know his stuff, but yeah, he reckons he said straight away it was a fuel/injection problem but after spending weeks working on it and checking everything (including the replacement of the MAF and fuel pump), he says they have got it as good as they can. I might have to take it down to perth or something if i cant get it going....

[SLEEPR85]

Just out of interest..... did you change your ECU to a RB25 one, or do you still have the RB20 one still in? How much boost were you running on the stock ECU? Anything above 11-12 will cause major head drama's on a stock computer....

[Fox - R32]

Just out of interest..... did you change your ECU to a RB25 one, or do you still have the RB20 one still in? How much boost were you running on the stock ECU? Anything above 11-12 will cause major head drama's on a stock computer....

Yeah thats the thing, i got the car after the conversion and all that had been done, so i am not sure how much they actually changed over. I will have a look at the box tonight and take the codes/names/specs off it and look it up. I was running 12psi when i got it dyno tuned, and it ran fine with that for a good 6 months untill it started playing up.

Like i said before, its just strange how the mech reckons when he boosted the fuel pressure up to 50 pound on the rails (by restricting the return line) the car didnt miss a beat... do you reckon that makes it seem more a mechanical problem?