Jump to content
SAU Community

Resolved Misfire In R34 Gtt - Rb25det Neo

V28VX37

By V28VX37,
in General Maintenance

 Share

Recommended Posts

V28VX37 Veteran

V28VX37

Posted
Posted

Hi all,

I recently got an R34 GTT and had a niggling misfire problem with the RB25DET Neo. Once warmed up the engine did an occasional shudder on idle and also sometimes felt bit sluggish and seemed to hesitate when accelerating in higher revs. After a couple of weeks of sleuth work this is now resolved, thank goodness.

I trawled through heaps of existing SAU threads for advice:

Here's a list of various things we tried:

  • Check ECU for fault codes
  • Remove engine cover and valley cover and clean underneath
  • Inspect and tape up coil packs
  • Replace spark plugs (mine had 2-year old NGK PFR6A-11 platinums which I replaced with NGK BCPR6E-11's on stock 1.1mm gaps)
  • Change fuel (fill up) several times (BP Ultimate 98)
  • Reset ECU several times
  • Conduct data logging using Nissan DataScan
  • Visually inspect air box, air filter and AFM
  • Re-gap spark plugs down to 0.7-0.8mm
  • Change engine oil and filter (Motul 4100)
  • Fit new genuine Nissan O2 sensor

However it wasn't until the clever chaps at Chasers re-checked the fault codes (after the car had stalled on idle all by itself, it's an auto) and chucked the car on the dyno that the root cause revealed itself. The Crank Angle Sensor (fortunately) threw and error code and on closer inspection the trigger wheel was found in physical contact with the optical sensor! The CAS was prompty rebuilt using parts from another unit.

The guys also concluded that whilst externally fine the stock coil packs are starting to get weak and they re-gapped the plugs down further to 0.5mm as a temporary solution until I get a new set of coils.

Due to the coils the idle is still a bit choppy intermittently but the car now pulls smooth all through the rev range and has its full power back. It returned a nice round 150 rwkw on the dyno, which I think is spot on for a stock GTT.

Unrelated to the misfire, the original O2 sensor was stuffed too and replacing it has improved fuel economy straight away. I got my OEM replacement from Kudos Motorsports.

Lastly, the only things I can think of that we didn't try:

  • Test coil pack harness with multimeter for faulty wiring
  • Replace coil packs one by one to identify faulty one(s)
  • Check fuel filter

I hope this helps someone else diagnose and solve the misfire issues. Big hat tip to Chasers for helping me out on this!

Cheers

  • Like 1
Shazza24 Proficient

Shazza24

Posted
Posted

Gee guess i got lucky as i had a minor idle problem (R33 S2 Man) and changing the plugs fixed it! However i suppose any car coil packs that have done 90,000+ or 10+ years probably need to be changed. The CAS needing to be rebuilt is a good one, handy to know that though! :D

  • 5 months later...
V28VX37 Veteran

V28VX37

Posted
  • Author
Posted

The guys also concluded that whilst externally fine the stock coil packs are starting to get weak and they re-gapped the plugs down further to 0.5mm as a temporary solution until I get a new set of coils.

An update on that pesky little misfire on idle that I had for the past couple of months.

I bought and tried 2 cheap sets of second hand OEM coil packs, on each occasion I thought they helped at first, but really don't even bother. OEM coil packs aren pulled out for a reason.

The car also started throwing the classic TCS+slip+engine light combo, too (ignition circuit).

As the penultime try I cleaned up the AAC valve just to confirm it wasn't that. Affirmative.

So I finally bit the bullet and replaced the original coils with brand new Yellow Jackets and put in a fresh set of BCPR6E-11's gapped to 0.9mm.

The misfire on idle IS GONE. About friggin time too!!

  • 3 years later...
  • 9 months later...
V28VX37 Veteran

V28VX37

Posted
  • Author
Posted

Yeah well the misfire is back, has been for a while, mostly on idle. The car hiccups when sitting at the lights. High RPM is better (although not perfect) so I don't think it's CAS related.

Is it even possible to make an RB25 run smoothly without misfire?? I mean 100%, not 99% or 95%? This is silly, I never ever had misfire issues in my modded LS1...

I am starting to wonder whether I need new coil packs, again. As far as I can tell the options are:

  1. OEM. I have had 3 second hand OEM sets, never worked 100%. New ones are pricey. Not keen.
  2. Aftermarket. Currently running Yellow Jackets that were bought new. I can't imagine there being much difference between brands around the $500 mark?
  3. Top shelf aftermarket. Something like the Ignition Projects ones: http://ignitionprojects.com/catalog/ip-coil/nissan/skyline-nissan-ip-coil - Is anyone running these? Dino reported good results with I-P on Speedhunters - http://www.speedhunters.com/2014/10/a-spark-of-efficiency-project-gtr/ . Hellishly expensive though.
  4. LS1/LS2 coils conversion. Something like this: http://www.mojoperf.com/drupal/node/21 - unfortunately not available for the NEO.

I'm starting to lean towards the LS coils, kind of over the RB ones... Any recommendations??

Or maybe it's not the coils, who knows with these things :wacko:

tridentt150v Grand Master

tridentt150v

Posted
Posted

If you tried coils of all different types etc like you have..............and it didn't permanently fix the problem then why would you keep thinking its coils??? my guess si you are disturbing the problem when you did this and thats what fixed it temporarily.

Try other things, get your injectors checked!!

Also next time it misfired pull coils or leads off one at a time and see if it makes a difference - difference = coil OK, no difference then that cylinder is the one to look at If no difference irrespective of cylinder then the problem is not an injector/coil/spark plug..

Clean your MAF.

Check your fuel pressure for regulator agnd/or pump.

Change ECU's do a swap.

Check your coil loom/wiring, check all the connections, pull on your wires and see if they are still solid and fixed/cripped to the connectors etc

Get a compression test both a warm and a cold one and check the results [should be stuff on the www telling you how to use the info]

Start trying to isolate the problem, if you can get it down by process of elimination you will win.

My RB33 idles and runs smooth as, plus doesn't miss a beat really and I have 300rwkw and a WMI system etc etc etc the RB motor is not the problem [unless you have a motor issue].

  • Like 1

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Duncan
      R33 GTR running -9 with no tune

      By Duncan · Posted

      Sounds like you've got an interesting adventure ahead here with local support if you have trouble! My guess is that, unboosted, you will be OK with a small upgrade like -9. What will happen is that once the stock ECU sees more airflow than it expects it will add a heap of fuel and pull a heap of timing to be safe because it can't understand how it could get that much air without there being an issue. You will see clouds of black smoke and it won't pull hard through the midrange and top end. So, overall it will be a bit frustrating but should be OK. If you are still nervous set the base timing back 2o through the CAS, but it will be even more sluggish everywhere. As said above through...this is not my guarantee your engine won't be blown into a million pieces, leaving you looking for very hard to find parts A better idea is get a computer with logging ASAP, wire in a wide band O2 sensor and a use remote tuner. I've done multiple cars this way and while it is not as good as a specific tune on a dyno they can get it 90% right. I'd suggest if you can afford an R33 GTR these days you can afford an ECU and tune. And if you can't afford that you sure won't be able to afford the rebuild if it goes bad in the meantime,.  
    • Duncan
      New kid on the block

      By Duncan · Posted

      Yeah it would be nice if someone took the time to put that sort of information together, but there are a lot of variations in looms. I think you are making this way hard for yourself if you just want to get it running....sourcing an SR20 with the right wiring will be a billion times easier than matching the RB loom to an S15 chassis. If you do end up going this way, you just need to trace every wire in the loom with a multimeter, 95% of them will go to a location you can confirm at the ECU.....and then post it up for the next person who needs it  
    • Duncan
      Coolant leak?

      By Duncan · Posted

      Just top it up with water, and keep a general idea of how much you added. It is normal for water to be pushed into and pulled out of the reservoir through the cap, and it should not be more than half full or it will be likely to overflow when hot. Any decent mechanic can do a pressure test of the cooling system to confirm if you have a leak. Keep in mind if it is only leaking a little and when hot it may well evaporate before you see it hit the ground
    • GTSBoy
      Coolant leak?

      By GTSBoy · Posted

      I'd ask the shop what they used and use that. Mixing coolants is sometimes OK, sometimes not, and you have know the details of each coolant to know whether it's a good idea or not.
    • Chupapy
      Coolant leak?

      By Chupapy · Posted

      Is it alright to top up with just another green coolant?
×
×
  • Create New...