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RB25DET not pulling to the redline??

inissane

By inissane,
in Engines & Forced Induction

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inissane Proficient

inissane

Posted
Posted

Hi peoples,

I am trying to help my old man diagnose a problem on his R33 RB25DET. It seems to be running lean, an a/f problem that has possibly increased over time and now shows its head through a loss of power above say 4800rpm to the redline. Below this rpm it seems fine, its just feels like its being held back a bit up there and sometimes worse than other times. The car is completely driveable no stalls or serious spluttering, just not pulling hard to the redline like it should and possibly unburnt fuel going through

timing or mapping??

sensors - afm, O2, crank angle

coils, spark plugs - coils checked out fine apparently

The car has had steady state modifications for years which include only 3" full exhaust and HKS pod, stock boost 7-9 psi max I guess, and I noticed speed limiter removed otherwise stock ecu I assume.

Been treated and serviced well, I have a readout from the diagnostics if anyone could have a sqiz, I guess the afm/O2 sensor readings are about what would be expected at those rpm?? otherwise those sensors could be the problem but I guess they should have noticed or checked those external sensors were ok?

computer codes were all clear too

RB25DET diagnostic readout

I guess the bottom line may be get her on a dyno, but I would appreciate some ideas or experiences from other RB25ers!!

cheers

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paulr33 Grand Master

paulr33

Posted
Posted

wow cool diag, where did that diag printout come from? a nissan dealer?

02 sensor wont cause the problem your experiecing. do you get any smoke or wierd noises, any whining or spluttering on boost etc?

inissane Proficient

inissane

Posted
  • Author
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yeh he took it to a Nissan dealer, there is also some pinging around but no obvious smoke and not really a huge amount of jerkiness - it seems to come on boost fine, pull up to around 4700-4800 rpm then just not take advantage of the boost at those high rpms cause of timing or mapping im thinking, but this obviously makes a fair few assumptions.....

I could swear I can hear some fuel going through the muffler when its doing it badly

Zahos Mentor

Zahos

Posted
Posted

The most common R33 misfire problem is due to cracked coils.

This usually causes the car to run rich though, not lean.

Anyhow give this solution a try, it will only cost you $5 or $10

http://www.skylinesaustralia.com/forums/sh...ead.php?t=51046

Also gap your spark plugs down to 0.8 mm if you haven't already.

inissane Proficient

inissane

Posted
  • Author
Posted
The most common R33 misfire problem is due to cracked coils.

This usually causes the car to run rich though, not lean.

Anyhow give this solution a try, it will only cost you $5 or $10

http://www.skylinesaustralia.com/forums/sh...ead.php?t=51046

Also gap your spark plugs down to 0.8 mm if you haven't already.

cheers for ideas guys,

my first idea was coils also but apparently they checked ok and they reckon the problem is elsewhere, and it is pinging etc

Zahos Mentor

Zahos

Posted
Posted

Don't mean to drag the issue of the coils on, but when mine were *REALLY BAD* (all 6 crackd, and 1 had a missing spring, and the contact surface oxidized - went completely green), the car would not go past 3,500 - 4000 rpm at all. Not even if you pushed it.

They connected it up to nissan consult, and no error codes.

On visual inspecion the cracks could not be seen on this particular set of coils.

I swapped them with a set that had huge cracks, and were covered in Araldite. I still have that set of coils in there now.

How did you test/check coils? (Just to be sure)

  • 2 weeks later...
inissane Proficient

inissane

Posted
  • Author
Posted

haha....ok... ive decided nissan dealer mechanics are like monkeys with spanners :chairshot , I guess they just do regular services on normal nissans

took it back to Powerplay where its usually serviced, threw a set of splitfire coils on and a r34 gtr fuel pump and its pulling like it used to :)

thanks for the help and persistence with the coils thing, oh and also new spark plugs for good measure

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