Missfire Symtoms But Only In Cold Weather Rb25det

[johnny443]

Hi guys,

I seam to be having a missfire or missfire like problem with my r33...

now before someone posts up reply to search missfire i already have and nothing relates to my issue

what seams to be happening is when its warmer weather the car runs really nicely doesnt skip a beat but as soon as it cools down just a bit it starts to splutter on and off through the revs and sometimes if i dont back off spltters till redline its very similar to a screwed coilpack problem but from what i gather why would the coil pack work in warm weather but not in cold.. also i just recently changed all my spark plugs and sealed up the coilpacks with high temp silicone to stop the spark jumping and hitting the head i cant see it being a fuel issue for the same reason the only thing i can think it could be is the AFM would this cause this type of problem?

current mods are:

3inch turbo back exhaust

podfilter/cold air intake

front mount

boost tap

boosting at 10psi ATM have kept a close eye on the boost in difrent weather conditions and it stays at 10psi in cold and warm weather so its not were near hitting the boost cut or spiking

any help would be greatley apreciated lost for ideas

[lach88]

have you tried taking the boost tap out? and running standard boost? does it missfire and sputter through the rev range if you are not building full boost?

[defari]

vac leak - double check all seals / clamps are secure

[PM-R33]

Cold air is denser than warm air and therefore containers more oxygen. This makes your car perform better (hence why your car pulls better during the night compared to during the day).

This increase in oxygen is obviously enough to get past the threshold of your ignition system.

This is probably the most common problem on Skylines due to coilpacks that are getting old. Putting silicone on them does nothing to help them if the problem is internal.

What spark plugs have you got in there? If you have a 1.1mm gap you should go down to a 0.8mm gap and that shall solve your problem.

If you are allready running a 0.8mm gap than your coilpacks will need changing. This is why you see nearly every Skyline running Splitfire coilpacks (they are cheaper than brand new OEM ones).

Edited November 12, 2010 by PM-R33

[johnny443]

I don't think the boost tap is causing any problems like I said when I say cold it's not freezing weather it's just cool when it's a 30 degree day it runs fine yet when it drops down to bout 25 it start and the more it drops the more it does it I had iridiums in it and was told by a Mechanic to change them to standard ones I'm not sure what the standard gap is.. I never gapes when I put them in I don't have a vac leak because the boost gauge sits on -20 when the car idles which from what I know is good

[RBceffy25]

rich and retard. block off you CAI tonight and go for a drive.

[johnny443]

OwSo I should have it suckin in the air from the engine bay ? What.would be.the proper.way to fix.this.? This did.start happening.since I put the pod and cold air.intake on it I ran a peice of intercooler pipeing from wherr the.stick intercoolet used.to come back and made a box for the filter

[RBceffy25]

Cold air is denser than warm air and therefore containers more oxygen. This makes your car perform better (hence why your car pulls better during the night compared to during the day).

This will also max out the standard airflow meter because of the cold air coming in through your air box. This will cause the ecu safeguard 'rich & retard', which enriches fuel mixtures and retards the ignition timing in an attempt to safely reduce the amount of boost the thing is making. 10psi in the day and 10psi at night are two different thing because the air is more dense at night and the AFM recognises this hence R&R.

This same thing happened to me when I fit my FMIC and CAI. I had to immediately block my massive (bout 5") cai just so i could drive it up the road and back.

OwSo I should have it suckin in the air from the engine bay ? What.would be.the proper.way to fix.this.? This did.start happening.since I put the pod and cold air.intake on it I ran a peice of intercooler pipeing from wherr the.stick intercoolet used.to come back and made a box for the filter

If you can, fit the standard air box with panel filter or

get a mines or equivalent standard ecu with boost cut, rev limit, R&R etc. all removed or

get an Apexi AFC or

get nistune or

just fork out and get a complete after market ECU... like what you should have done first if you had plans to get any more than standard power...... just as I learnt the hard way

But seriously, just test it tonight by blocking it off and go for a blat.

EDIT: Because you have a FMIC you shouldn't have any intake temp. problems with the CAI blocked off.

Edited November 13, 2010 by RBceffy25

[RBceffy25]

Also try cleaning your AFM

[johnny443]

Thanx guys really appreciate the help going to put the stock airbox in today and see over the next few days when it cools down see if it makes a difference.. I've already cleaned the Afm a few weeks ago with circuit cleaner didn't make any diffrence!

[johnny443]

changed it back to the airbox today took it for a spin tonight and ended up being alot worse than it was with the pod!.. i starting to beleve this would be a faulty AFM

can any 1 suggest good skyline mecanic workshops which i could take this problem to... im in the sydney area dont mind traveling a bit

[mjscar]

Try gapping your plugs to 0.7 mm. I had major misfiring problems as well when I put a turbo on my 25DE and I brought the car back to my tuner and he said gap them plugs to 0.7 mm from 0.8 mm and it should be mint. Never had a problem since. Still amazed how much 0.1 mm made a difference because my misfire was reaalllly bad before.

Edited November 14, 2010 by mjscar