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Long Term Ongoing Problem

Alf

By Alf,
in Engines & Forced Induction

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Alf Proficient

Alf

Posted
Posted

The motor is a RB30/25 that is less than 5000ks old and in a 32 GTST

  • R33 RB25DET S1 head
  • PFC for the above head
  • std cams
  • std injectors
  • CPC plenum with Q45 TB
  • Q45 AFM
  • GT35R 0.82
  • approx 9:1 comp
  • R33 RB25DET S1 loom modified to suit R32
  • Using 2 tensioner setup with gates belt

The following has checked out ok...

  • Comp test (175psi cold)
  • Leak down test (less than 5%)
  • All timing components triple checked
  • head removed and rebuilt, nothing visually wrong
  • injectors cleaned and working
  • tried CAS, coils, igniter, TPS from working motor
  • tried PFC in a stock R33 with factory settings (works fine)
  • Tried stock R33 RB25DET ecu (with stock AFM) and the problems continues
  • gapped plugs to 0.8, 0.7 0.6, also tried BKR7E and BCPR7ES
  • Fuel pressure is fine at 320 kpa
  • new battery & all earths checked
  • Tried a PnP Link G4 ecu
  • removed TB and see nothing visually wrong inside plenum
  • Turbo, manifold and exhaust checked, no blockages
  • Get spark at all coils ( turn cas with ign on)
  • changed fuel (98)
  • changed fuel pump
  • Changed fuel filter
  • Cleaned out fuel lines
  • removed alarm
  • disconnected wideband and thermos
  • Adjusted cas and TPS
  • Wiring to Q45 afm checked and replaced
  • cams dialed in and checked with dial gauge
  • Every wire in the engine loom checked

This has been going on for over a year now and have not been able to drive it. It backfires through exhaust and intake, it seems like the timing is out but the mechanical timing is spot on and the timing light shows its firing approx 15-20 deg at 1000rpm. The PFC shows that the ign timing doesnt move from 2-3deg. I have tried making adjustments in datalogit and in the Link software without any luck.

I'm on the central coast NSW, have consulted with the local gurus and they are stumped...

Any suggestions are appreciated as I spent over 20K on the motor and wont be letting it go.

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https://www.sau.com.au/forums/topic/399241-long-term-ongoing-problem/
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Alf Proficient

Alf

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  • Author
Posted (edited)

Backfire on accel and decell. Opening the throttle makes no instant change to revs, you need to open the throttle then crank it and feather the throttle to keep it going. It's no different when cold or warm.

When I'm lucky it will idle but at low revs ie 400rpm and struggles to keep going. It's been months since it's been driveable as it coughs and splutters and dumps plumes of unburnt fuel out the exhaust.

Today I cleaned up the plugs and checked the timing against the PFC hand controller and the timing on the gun matches the timing on the PFC.

Edited by Alf
Lithium Grand Master

Lithium

Posted
Posted

What kind of ignition system are you running? Sounds like what I'd expect if someone had wired the ignition outputs out wrong, or wired leads up in the wrong cylinder order.... sometimes people are thinking firing order when they say "1,2,3,4,5,6" and sometimes they are thinking physical cylinder number. If you wire something up where the two terms contradict then most diagnosis won't show anything wrong, as everything is working exactly as its meant to - just the point the plug has been wired to fire at isn't going to result in very efficient combustion ;)

Alf Proficient

Alf

Posted
  • Author
Posted (edited)

Std Rb25 ignition system and std coils. Also have splitfires and hasnt made a difference.

I'll double check the wiring from the coils to the igniter to the ecu.

Before this problem occured , it started first go and went hard.... it did have a high ilde so I did this http://www.skylineow...ad.php?t=161490 and this is when the problem started. I put the TB back to the way it was and still had no luck.

Edited by Alf
EAT26 Community Regular

EAT26

Posted
Posted

Just curious but in the whole list you have listed you have not said you have tried a new/another AFM? I use to have issues with my car stalling at idle before of the AFM, I changed the AFMS and problem went away. I also adjusted the Idle control to idle it a little higher than stock just to keep it good.

Alf Proficient

Alf

Posted
  • Author
Posted

I have tried using a stock afm and making the neccessary adjustments in the ecu without luck. Also tried the Link ecu (with 2.5bar map sensor) and the result is still the same

When it was running I had tried every method of adjusting the idle, it did lower/increase the idle but still not smooth, its also the case with the LINK with it's map sensor which led me to the pushrod in the throttle body may be the problem. There was never an issue with tuning the motor, it was just the idle then.

However it doesnt explain how the ignition system is NOW not firing right.

51NNA Community Regular

51NNA

Posted
Posted (edited)

I know you said you checked the timing at 1000 revs but have you had the timing light on it while revving it? Sounds like its retarding the timing and leaning out. Whats the AFR's doing on the dyno? Also whats your VVT connected to?

Edited by 51NNA

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