Feels Like Misfire But I Think Its Fuel Shortage At High Revs. Help Please.

[nosking_178]

hey guys.. i used to have a misfire problem with my car r32 skyline gts (non turbo) about 4 months ago. but i fixed it and now it feels like it is misfiring at higher revs again (full throttle).. but i dont think it is misfiring.. i think it has something to do with fuel shortage. it has happened about 1 or 2 months ago and i changed the fuel filter and it went away but now its back ..... :S

wen its at high revs and at 90% or full throttle.. it makes a put put put sound...

low throttle runs fine and this problem occurs on some days usually the days when i run it hard... :S:S:S::S::S

any help is much appreciated!

[Birds]

Have you investigated the spark plugs at all? How recently were they changed? Were they appropriate heat range? What gap were they?

Might pay to test your fuel pressure. Injectors may be leaning out too.

I have a similar problem that occurred just lastnight after lots of driving, but was gone this morning. This suggests it was heat related so I'm putting it down to my spark plug heat range.

[nosking_178]

hey thanks for the input. much appreciated...

when my car was misfiring 4 months ago.. i changed the spark plugs, coil packs, coil pack ignitor module. and i have done approx 3000 since then. im not sure what gap they are but my mechanic changed them.. think he used high performance ones.. cant remmeber what their called exactly tho.. mayb iridium but they should be suited for my car since he knows what he is doing.

oh and 1 or 2 months ago.. it used to do it when my engine was cold temp like morning starts etc..... i realised after i had to give it full throttle and to overtake sum 1 and it made a put put noise :| and now since then i changed the fuel filter and now its back after a month or 2.

how do i test fuel pressure that sounds a good source to my problem.? and could it have something to do with fuel pump? or nar.. \

and would u reconmend me using fuel injector cleaner (those additive in a bottle)

cheers for ur help mate. =]

[Birds]

It might pay to check the gap they were at or the heat range of them. I have Iridiums in my car but they are only heat range 5 which is probably too low, yet they were recommended for my car by the NGK catalogue. Normally they do fine but I did alot of high RPM driving lastnight which may have overheated them, lagging their performance in the mid-high RPM range. This would be akin to an intermittent problem.

Fuel pressure can and should be tested at the rail...I'm not that familiar with these engines yet but there should be a fuel purge valve on the rail somewhere that you can attach a pressure gauge to for a reading. It can certainly be a fuel pump problem, as a faulty pump will not be supplying the required pressure to deliver enough fuel at high RPM. This would be akin to a constant problem, not something intermittent.

Injector cleaners in a bottle...meh...they aren't fantastic at cleaning and some of them even leave deposits in your injectors that worsen the problem down the track. The only way to properly clean injectors is to take them out and have them serviced/reconditioned.

[nosking_178]

a couple of days been driving.. my problem has been gone. But im sure it will come back again..

ill change the fuel pump and use injector cleaner sumtime this weekend when i get a chance and let ya know how i go... and if it still misfiring... ill change my spark plugs. cheers for all your help mate.. ill update ya on how i go. =]

[nosking_178]

hey sorry about the delay on this post i havent bad a chance to change the fuel pump until today.. but unfortunately this did not solve my problem.. it runs alot better but the problem still exist..

ill have a loook at my spark plug..

and do u think the air/ fuel sensor has sumthing to do with this problem?

[Moodles2]

The "Air/fuel sensor", do you mean the Oxygen Sensor? Nope shouldn't have any effect on misfiring. Give your AFM (Air flow meter) a clean.

[CARSICK]

The coilpacks you changed...

Were they new or second-hand?

[nosking_178]

hey the coil packs were new. so i dont think it would be that causing the problem....

ill clean my AFM with carby cleaner??? would u suggest using that or would that damage..

oh and umm yerh i mean the oxygen sensor, my bad. the auto baurn staff told me that it might be that causing my problem.

i found it onli like misfires wen 90% or full throttle... and onli on days when idrive it hard.. it will start mis firing at full throttle..

low/mid throttle is perfectly fine.. :S im confused

any advice is much appreciated!

[nosking_178]

oh and when i get a chance ill check what spark plug my mechanic used... from memory they are denso brand but i got no idea what gap or heat rating they are.. ill have a look on tues since i got a day off.. and let youse know.

[PIOTREK]

mate sounds like it would be cheaper (50-100 bucks) and get it checked on the dyno! sounds like u are pouring money into your car without finding the problem.

On the forumns you can get pretty good opinions, and some pretty bad ones (NOT POINTING AT ANYONE DIRECTLY). Good that you are changing all these things- but its over kill.

I would be one to say thats its the coil pack- but since you changed it dw!

Good luck and hope that u fix your problem!

[nosking_178]

thanks for your advice... any place suggested to go for a dyno tune????????? im from geelong and not many place i can go to that know about skylines..... melbourne is prob the next closest resort to go for a decent dyno tune place but my car prob wont make it up there

i thought dyno tune wud have been alot more.. thats why i been trying to avoid it............

but im quite certain that it is the ignitor module playing up because as i move the wire it will run smooth and when i take my hand off it will misfire and shake lik crazy...

my mate's friend knows some1 who has a r32 as well so his gnna see if i can swap the module with his to see if it fixes it up.... then ill buy a ignitor module

[Benzino33]

thanks for your advice... any place suggested to go for a dyno tune????????? im from geelong and not many place i can go to that know about skylines..... melbourne is prob the next closest resort to go for a decent dyno tune place but my car prob wont make it up there

i thought dyno tune wud have been alot more.. thats why i been trying to avoid it............

but im quite certain that it is the ignitor module playing up because as i move the wire it will run smooth and when i take my hand off it will misfire and shake lik crazy...

my mate's friend knows some1 who has a r32 as well so his gnna see if i can swap the module with his to see if it fixes it up.... then ill buy a ignitor module

Isnt there anything around Geelong thats got a dyno? If u wanna go to Melb, theres a thread somewhere if u do a search, shows all the tuner shops and jap wreckers around there,..you could check out status tuning, m-spec, race pace or something. Ive heard good things about them

[mad082]

they don't have to know about skylines to be able to tell you if it is running lean. all they have to do is put it on the dyno, stick their wideband o2 sensor up the exhaust and then do a few runs.

[nosking_178]

oh okay.. that helps heaps...

ill swap the ignitor module with a mate 1st to see if its the problem if not ill give the dyno a go... on my next day off.. and ill let ya'll how go

[nosking_178]

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