Jump to content
SAU Community

Recommended Posts

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

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...

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...

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:

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


  • Similar Content

  • Latest Posts

    • The rain is the best time to push to the edge of the grip limit. Water lubrication reduces the consumption of rubber without reducing the fun. I take pleasure in driving around the outside of numpties in Audis, WRXs, BRZs, etc, because they get all worried in the wet. They warm up faster than the engine oil does.
    • When they're dead cold, and in the wet, they're not very fun. RE003 are alright, they do harden very quickly and turn into literally $50 Pace tyres.
    • Yeah, I thought that Reedy's video was quite good because he compared old and new (as in, well used and quite new) AD09s, with what is generally considered to be the fast Yokohama in this category (ie, sporty road/track tyres) and a tyre that people might be able to use to extend the comparo out into the space of more expensive European tyres, being the Cup 2. No-one would ever agree that the Cup 2 is a poor tyre - many would suggest that it is close to the very top of the category. And, for them all to come out so close to each other, and for the cheaper tyre in the test to do so well against the others, in some cases being even faster, shows that (good, non-linglong) tyres are reaching a plateau in terms of how good they can get, and they're all sitting on that same plateau. Anyway, on the AD08R, AD09, RS4 that I've had on the car in recent years, I've never had a problem in the cold and wet. SA gets down to 0-10°C in winter. Not so often, but it was only 4°C when I got in the car this morning. Once the tyres are warm (ie, after about 2km), you can start to lay into them. I've never aquaplaned or suffered serious off-corner understeer or anything like that in the wet, that I would not have expected to happen with a more normal tyre. I had some RE003s, and they were shit in the dry, shit in the wet, shit everywhere. I would rate the RS4 and AD0x as being more trustworthy in the wet, once the rubber is warm. Bridgestone should be ashamed of the RE003.
    • This is why I gave the disclaimer about how I drive in the wet which I feel is pretty important. I have heard people think RS4's are horrible in the rain, but I have this feeling they must be driving (or attempting to drive) anywhere close to the grip limit. I legitimately drive at the speed limit/below speed the limit 100% of the time in the rain. More than happy to just commute along at 50kmh behind a train of cars in 5th gear etc. I do agree with you with regards to the temp and the 'quality' of the tyre Dose. Most UHP tyres aren't even up to temperature on the road anyway, even when going mad initial D canyon carving. It would be interesting to see a not-up-to-temp UHP tyre compared against a mere... normal...HP tyre at these temperatures. I don't think you're (or me in this case) is actually picking up grip with an RS4/AD09 on the road relative to something like a RE003 because the RS4/AD09 is not up to temp and the RE003 is closer to it's optimal operating window.
    • Either the bearing has been installed backwards OR the gearbox input shaft bearing is loosey goosey.   When in doubt, just put in a Samsonas in.
×
×
  • Create New...