Jump to content
SAU Community

Recommended Posts

hey im trying to hunt down a miss fire in my rb25det

the car is a stock rb25det making 470rwhp at 26psi

last 3-4 weeks its been getting bad, now its time 2 do something about it.

basically the car from cold will start up and run on 5 cyclinders for first 10secs then clear up and run fine.

i can drive around off boost and it will run fine. As soon as i give the car a hard time and thrash it, i can pull up and on idle its back to 5 cyclinders.mind you it runs perfectly fine under load/boost

ive narrowed it down to cyclinder 6 which is the cyclinder not firing.

ive tried new injectors,coilpack wiring harness etc

injectors have been cleaned etc and new seals.

ive done a compression test and its good came back with 150-155 from 1-6

anyone else got any ideas? some ppl ive talked to think its lifter problem in cyclinder 6?

Edited by methz
Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/
Share on other sites

4350772539_55ff96415a_o.jpg&sa=X&ei=uotlTsuKKMLOmAXolZGaCg&ved=0CAUQ8wc4AQ&usg=AFQjCNGlgx_MfDkMMdcgSkJIa3LWOkL0Zw

Simon is making 500+hp on a stock motor? Misfiring could be caused by many things but it seems you've tried the basics. I will be keeping an eye on this thread to see how it progresses. Keep us posted. What I would suspect is the spark plug or coil back. Next would be wiring. Next would be CAS(could be playing up?) Sounds electrical to me. My car had similar symptoms on startup. It would sound like its missing a cylinder or even two and after a few seconds they all kick in, my spark plugs were on their way out. Try gap your plugs closer see if that gets rid of the misfire.

Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/#findComment-6002873
Share on other sites

plugs are about 500kms old bk7re always used them.

leak down test might be on the cards then, might ask my tuner 2 perform this.

yes 26psi thru gt35r on a stock rb25. i dont always run this boost. only turned it up for a dyno day not long ago.

running 1.75bar atm.

Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/#findComment-6002980
Share on other sites

At that power level I am assuming normal 98 pump gas? Simon is getting away with it on an ethanol mix, petrol would probably be a bit much for the crap fuel we get in this part of the world :(

+1 on compression test.

Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/#findComment-6003033
Share on other sites

yes pump 98 bp ultimate

car has been on big boost and 400hp for a few yrs now.

ive done 2 compression test's and both came up fine 150-155 across all 6.

leak down i have not done, i dont even know someone with the right tool 2 do it.

Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/#findComment-6003068
Share on other sites

Try a CAS and see. Just borrow a mates one if possible.

Have u upgraded the valve springs?

Does the engine tick when its misfiring?

Any smoke?

Do a compression test when it starts to misfire if u can. Maybe a valve seat issue

Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/#findComment-6003438
Share on other sites

Gonna try new CAS 2morrow morning.

Valve springs are stock

only ticking noise is from the injectors, as far as im aware

no smoke at all.

ill get it 2 run on 5 and do a compression test then and see wot it comes up with.

yeh my tuner thinks a lifter or valve or something along those lines in cyclinder 6

Link to comment
https://www.sau.com.au/forums/topic/376360-rb25-miss-fire/#findComment-6003477
Share on other sites

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

    • This. A 3d wheel alignment is like $120...just take it to the shop. Since theres probably multiple adjustments that need to be made after changing something. Mine has front/rear lower arms, traction rods, tension rods, camber arms, toe arms, front upper arms, hicas kit, sway bars and coilovers. I measure from the edge of the bolt holes on the originals and set the same length on all the adjustable stuff to dial it as close as I could to OEM. Took it straight for alignment; it didnt feel right at all...after alignment, it feels perfect. Similarly i've just changed the springs on another car; and I still needed multiple adjustments to bring it back in spec.
    • A full Veilside kitted JZA80 Supra in Meriken park in Kobe city a few weeks back
    • Its a well known brand in New Zealand; its a rebrand of the Rhino RAV3.  I don't know what the wiring difference *is* between the rev.1 (installed about 15 years ago) and rev.2; but as you say I would think its reasonable that it uses the same immobiliser relay circuits. I had a look but couldnt see a similar harness; but didnt move things around since I didnt want to mess with it   It was one of AVS well known Authorised Installers; I spoke to AVS themselves about it but theyre unsure hence seeking advice more so from the skyline community who are more familiar with the actual car and its wiring. Im in Auckland; but the installer is on the other side of the city so hes very reluctant to come back to even look at it to confirm something isnt connected into the wrong wire.  I dont want to drop the name since they *did* do a really good job for the most part. Everything is very tidy and he fully replaced all the alarm wiring, all the sensors, the wiring to the door motors, installed a switch which was never installed in the first place...really happy with the alarm install itself..just not this one issue. We all make mistakes, if it is the alarm, I just want my fuel pump getting proper switched, fused, power as it was; without having to shell out for an auto electrician to switch a wire and tell me it was the alarm. 
    • Even with the piston at TDC there was room for it to drop, but I don't think it can drop fully into the cylinder, the problem you have is that you need something pushing against the valve to hold it up so you have enough room to put the new stem seal on and the spring etc.  I used compressed air only because putting rope in the cylinder seemed a bit risky to me, I know people have done it countless times before like this. Overall it's a pain in the ass job. Honestly you'd probably be better off taking the head off because the risk of dropping something in the engine and the finicky-ness of it all is very stressful. If you are going to attempt it though i 10000% recommend a 36050 valve spring/keeper tool. I had both the traditional lever type and after doing 1 cylinder it was absolute pain to get those valve keepers in place, even with 2 people. That 36050 is amazing, you do have to push hard to get them in place but it works perfectly almost every time. Back to my actual issue I think my engine is just tired and old and the rings have gone bad. The comp numbers (cold, no oil) were: Cyl 1 -129psi Cyl 2 - 133psi Cyl 3 - 138psi Cyl 4 - 137psi Cyl 5 - 157psi Cyl 6 - 142psi   Cylinder 5 and 6 having the most carbon on them.
    • Who did you have do the installation? I actually know someone who is VERY familiar with the AVS gear. The main point of contact though would be your installer.   Where are you based in NZ?
×
×
  • Create New...