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Rb25Det Issues - Multiple Air/fuel/spark Problems

Brent

By Brent,
in General Maintenance

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Brent Enthusiast

Brent

Posted
Posted

Hi guys. Ok so a short run down on my situation.

Recently just put an RB25DET motor from a Series 1 Automatic R33 into my manual R32 GTS-t.

I drove the car that this RB25 came out of for around a week, NO ISSUES at all with the motor.

Got the loom made up by Sideshow Wiring (Jim) in Queensland.

Motor is standard, standard intercooler, turbo, no boost controller etc, 3.5" HKS catback exhaust, Blitz pod filter and splitfire coilpacks. Brand new spark plugs. Running the factory Auto R33 ecu.

Now my issues were that it was running really rich (like 200kms to a tank and blowing stupid flames), and had a fairly large and noticeable dead/flat spot between 3500-6500rpm (doesn't really feel/sound like it's misfiring though).

It would also want to stall if I approach the lights with the clutch in, but would get down to about 100rpm and pick back up again. Would only occasionally do this..

ALSO, if the motor was under fair load (say going up a hill) at around 3000rpm, the motor will cut out and quickly come back again.

So I thought, I'll replace one thing at a time and see how I can fix it.

New spark plugs regapped to 0.8mm, have tried three AFM's, two sets of splitfire coilpacks, o2 sensor, Bosch 040 fuel pump and finally an RB20 wastegate.

Nothing fixed any of the issues. So I thought I'll hook up the consult cable and look to see if there's any fault codes. Sure enough one came up, number 54 - A/T control. Was sort of happy, thought that the auto ecu may have been going into limp mode or something similar.

Managed to find a manual R33 ECU and plugged it in - ALL PROBLEMS VANISHED!

Or so I thought. The car was wanting to still stall when I approached the lights.. I found a bit of a leak in the pipe which leads off the blow off valve, replaced this and what do you know the stalling issue is fixed too!!

So I take the car out of the garage thinking I have fixed all issues, and I give the car a good rev onto an onramp... Nope, all problems appeared again. Running stupidly rich, really distinct flat spot (still making around 0.6bar boost) and a new problem also - very slight misfire when I lift the throttle off, can easily tell it's running on 5 cylinders for that quick moment.

I checked the faults with the consult cable and nothing has come up.

I really don't know what else to check/change, I've done as much as I can without spending obviously a rediculous amount of money.

I don't have the money to take it anywhere, nor get a PFC + tune etc.

Does anyone have any ideas as to what this could be? Surely it has to be something stupidly simple...

Any input would be greatly appreciated.

Regards, Brent.

Brent Enthusiast

Brent

Posted
  • Author
Posted

That was the number one thing I said I'm not doing. The car is standard, it shouldn't need a tune or aftermarket ecu.

The car WAS running 100% fine for about 20 minutes after I replaced the ecu with a manual one. And then got back into old habits, I guess because something is telling the ecu it has to run that way...

Godzilla34 Community Regular

Godzilla34

Posted
Posted

Well if you have a

Manual ecu with correct wiring loom, you say you have coil packs, airflow meter, I would check cat converter I'll have a better think about it and get back to you but I spose your right you probably

Don't need a tune im just saying of u had a power fc and a retune your issues would probably

Be fixed or atleast be more

Viable whilst tuning very hard to

Diagnose over the Internet with the provided info.

Godzilla34 Community Regular

Godzilla34

Posted
Posted

Well he has only replaced the ecu so as I

Said its hard to diagnose over the net. I doubt he has wired it incorrectly from the sounds of things I would say best bet a component is faulty once checked everything than I would check ecu .

Brent Enthusiast

Brent

Posted
  • Author
Posted

True. I forgot to mention that I'm running a de-cat pipe and my timing is set perfectly at 15 degrees. Could the cas still be faulty? It's one thing I haven't replaced as of yet... A mate today also suggested could be an earthing issue? Where the hell would I start to determine whether it's an earth issue?

Godzilla34 Community Regular

Godzilla34

Posted
Posted

i would be checking all areas of wiring that YOU have physically tampered with make sure the pinouts on the ecu have a proper earth. It may be a process if your not confident, if this where me i would spend a day looking through the faults than if nothing, take it to a mechanic.

mad082 Grand Master

mad082

Posted
Posted

It just occurred to me, do you have any sort of speed signal being sent to the ecu? That may be causing part of the problem if it isn't right. The ecu factors it in, as it does with the neutral switch. So if the ecu is getting the wrong signals then it will be using the wrong maps

  • 1 year later...
iruvyouskyrine Grand Master

iruvyouskyrine

Posted
Posted

Yes this did get fixed. It ended up being an issue with the wiring loom conversion. I can't remember exactly what the problem was, may have been something to do with the TPS from memory.

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