Arrgghh Impossible Misfire Problem :( Pls Help!

[Konrad]

My car has a mystery misfire that i've been chasing the cause of for a while now.

Done the following;

-new plugs, coilpacks, cleaned afm, throttle body and aac, checked for manifold/vacumn leaks, had timing checked, replaced fuel filter, fuel pump (walbro), ran injector clean through it...

The facts:

It only seems to do it at random times when it is very cold (say early morning/cool nights). The car idles a bit lower but sounds like a wrx, has a bad shake up to 3000rpm or so then it becomes unnoticable, however the car isn't very responsive still (so i assume the higher rpm masks the misfire). On letting the car drop down in revs (say pulling up to the lights) the car runs smooth as- so it seems to be a misfire under load.

It is not related to ENGINE temp it seems - i've just driven around for the best part of an hour and its still doing it even though my water temp is 78-80 degrees, oil pressure is normal etc.... infact for the first 5 min of driving my car tonight it ran perfect, then like flicking a switch it started to misfire.

It hasn't done this for a couple of months so i had thought the problem might have been solved but alas

I will also note that i have a slight pinging just as the car comes on boost, even under 'normal' engine operation without this annoying random misfire! However the car seems to rev well then, and its not a massive ping, i would describe it as a light scratching sound that goes away after a split second... on full throttle, full boost there is no pinging at all.

Possiblities

Could i have a faulty tps?

I've heard the crank angle sensor can fail, i searched but cant find any info on this - what happens when it fails and how does it fail? According to my blitz r-vit my timiing fluctuates between 0 and 5 degrees at idle, shoud it do that?? Is this reading correct?

Could another part of my ignition system be failing- maybe the ignitor? ( i have a series 1 r33 so its external).

I'm trying to think of anything else that might be affected by cold ambient temperature.... would appreciate anyones thoughts on this as i'm stumped

[12DFY]

The timing of my car at idle is more around the 30-35 degrees and drops down to about 15 degrees under load? Weird.

I have had dodgy Ignitor before and it just plain out melted??? Could always try swapping with a mates for a bit and see. Rule it out at least!

Have you conducted a compression test on the motor at all? Even though a problem in this area is most likeky going to be a permanent misfire, however they do weird things. Yet again Rule it out at least. Check timing etc as well

Same with the CAS, swap with mate and find out, cant hurt to cross more things off youre list of problems.

Good luck with it!

[BezerkR32]

Can you narrow the missfire down to one cylinder?

My car has a mystery misfire that i've been chasing the cause of for a while now.

Done the following;

-new plugs, coilpacks, cleaned afm, throttle body and aac, checked for manifold/vacumn leaks, had timing checked, replaced fuel filter, fuel pump (walbro), ran injector clean through it...

The facts:

It only seems to do it at random times when it is very cold (say early morning/cool nights). The car idles a bit lower but sounds like a wrx, has a bad shake up to 3000rpm or so then it becomes unnoticable, however the car isn't very responsive still (so i assume the higher rpm masks the misfire). On letting the car drop down in revs (say pulling up to the lights) the car runs smooth as- so it seems to be a misfire under load.

It is not related to ENGINE temp it seems - i've just driven around for the best part of an hour and its still doing it even though my water temp is 78-80 degrees, oil pressure is normal etc.... infact for the first 5 min of driving my car tonight it ran perfect, then like flicking a switch it started to misfire.

It hasn't done this for a couple of months so i had thought the problem might have been solved but alas

I will also note that i have a slight pinging just as the car comes on boost, even under 'normal' engine operation without this annoying random misfire! However the car seems to rev well then, and its not a massive ping, i would describe it as a light scratching sound that goes away after a split second... on full throttle, full boost there is no pinging at all.

Possiblities

Could i have a faulty tps?

I've heard the crank angle sensor can fail, i searched but cant find any info on this - what happens when it fails and how does it fail? According to my blitz r-vit my timiing fluctuates between 0 and 5 degrees at idle, shoud it do that?? Is this reading correct?

Could another part of my ignition system be failing- maybe the ignitor? ( i have a series 1 r33 so its external).

I'm trying to think of anything else that might be affected by cold ambient temperature.... would appreciate anyones thoughts on this as i'm stumped

[mad082]

it could be the fuel pump.

my mate had a blown coil pack that was due to the ecu being fried. he'd tried hooking up msd coils and fried the ecu. then when he went back to the stock coils it kept frying number 6 coil.

[T04GTR]

ok. refering to a kunt mitsubishi gto i fixed ... unplug the speed sensor on the gearbox and see if that does anything.

is the engine "tickie?" what oil are you using?

[Konrad]

Ok i swapped the ignitor for another one- didn't fix the problem.

I'm starting to think its not related to temperature as the car seems to have a permanent misfire now - all previous times it has 'come good' but now it has not.

I'm in the process of checking the physical condition of my splitfire coils and ngk iriway plugs. Have also changed the oil to motul turblight (it was due for a change anyway).

I dont have a multimeter so i cant check the electrical side of things, however i've used some contact cleaner to clean up some connectors...

It MUST be electrical to just appear like it does, and according to my blitz rvit - igniton timing is definatley 0-5degrees at idle. So this isn't normal?? could a faluty CAS do that? eg: ecu is putting the wrong timing into the car, or something to do with the vvt system on the r33??

bah this sucks..

And no new work has been done on it. The car sat for 3 weeks while i was out of town, and when i came back it drove perfect, only now (after 1 weeks driving) it starts to misfire.. The first thing i did was put a fresh tank of optimax extreme in (100ron) but that hasn't helped much.

[AlexR34]

Um just a suggestion are u putting premimum fuel cause if ur not it will missfire. my mates gtr use to missfire cause he didnt know he was spose to put premium, but u probably do anyway.

[kudos.motorsports]

If you can get your hands on another ECU.

[Konrad]

Ok another thought was 02 sensor..

And yes i *always* run 98 in the car, mostly BP ultimate with the occasinal tank of optimax extreme (100) when i can find some..

good idea andrew, will see if i can track one down

Still, going to have to drive this thing for another week at least like this.. unless it randomly fixes itself like its always done before!

[shanef]

I have a series 1.5 ecu up in the shed u can try (came off a 1996 33)

[T04GTR]

cool. unplug the o2 sensor.

also..

your ignition timing should be 15 degrees at idle.

(check with a timing light) through the little loop of wire near the ugniter

[BezerkR32]

If you can narrow the miss down to one cylinder then you can test the follwing, Injector pulse, ignition, Compression. could have a dickie injector or hydraulic lifter. until you can isolate the cylinder causing the problem, you will be chasing your tail.

The timing of my car at idle is more around the 30-35 degrees and drops down to about 15 degrees under load? Weird.

I have had dodgy Ignitor before and it just plain out melted??? Could always try swapping with a mates for a bit and see. Rule it out at least!

Have you conducted a compression test on the motor at all? Even though a problem in this area is most likeky going to be a permanent misfire, however they do weird things. Yet again Rule it out at least. Check timing etc as well

Same with the CAS, swap with mate and find out, cant hurt to cross more things off youre list of problems.

Good luck with it!

[Konrad]

I have a series 1.5 ecu up in the shed u can try (came off a 1996 33)

awesome you have pm

also, i dont have a timing light lol. My workshop said that the timing was reset to i think about 10 degrees, but my blitz r-vit (plugs into the consult connector) fluctuates between 0 and 5. Still, its always been like that - the values haven't changed so dont think thats the cause.. unless the ecu is thinking its runnning 0 degrees timing when its set at 10, maybe faulty sensor.

Coils and plugs were fine, usual carbon buildup, apart from one that sorta had a really fine waxy coat on it (was shiny, the other 5 werent), wasn't oil, i'm worried it could be cooked on coolant residue or something might have been my greasy hands that touched it before i could have a good look at it tho lol.

New oil is in, was running mobil 10-40, i've now got motul turbolight 10-40. Dont see how it will help my situation but guess it could keep those bearings a bit happier since they are under stress when driving with this misfire!

[R334door]

awesome you have pm

also, i dont have a timing light lol. My workshop said that the timing was reset to i think about 10 degrees, but my blitz r-vit (plugs into the consult connector) fluctuates between 0 and 5. Still, its always been like that - the values haven't changed so dont think thats the cause.. unless the ecu is thinking its runnning 0 degrees timing when its set at 10, maybe faulty sensor.

Coils and plugs were fine, usual carbon buildup, apart from one that sorta had a really fine waxy coat on it (was shiny, the other 5 werent), wasn't oil, i'm worried it could be cooked on coolant residue or something might have been my greasy hands that touched it before i could have a good look at it tho lol.

New oil is in, was running mobil 10-40, i've now got motul turbolight 10-40. Dont see how it will help my situation but guess it could keep those bearings a bit happier since they are under stress when driving with this misfire!

since you have checked your plugs,do a compression test, on that cylinder first with the shiny look on spark plug iand then another cylinder to compare .the compression if it is decent should be around 150-165.you might have a blown head gasket ,sounds like it.

[Konrad]

wont a blown head gasket use coolant, make the car overheat, smoky exhaust etc.. I used to own a cressida and it blew the headgasket twice in 1 year.

Well all my work today did nothing misfire is still there...

shits me that i gotta drive it like this for a week before i can do anything about it.

[Konrad]

pics of sparkplugs..

You can see the one that was 'shiney' (although it looks duller than the other 5 plugs) - it shows up in the pic better than i saw it in real life.

[The Dan]

pics of sparkplugs..

You can see the one that was 'shiney' (although it looks duller than the other 5 plugs) - it shows up in the pic better than i saw it in real life.

To start with you should only be running an iriway 6. The standard listed plug is a 5 so having 7's can be causing you problems. It's too great a jump to a colder plug. Try investing in another set of BCPR6ES-11's, gap 'em to 0.8 if you are running more than 12psi boost and see if it helps. If you are running 12 or less boost then keep them at 1.1. Go to any repco and ring me on the mobile and I'll give them my account number. You can have them for trade. Should only be about $3 each.

[AlexR34]

WOW DOOOOOOOOOOO NOT put optimax EXTREME, i contacted Nissan in japan about it and they said not to put optimax extreme because it contains ethanol and is very bad for the car. This was from NISSAN JAPAN themselves.

Ok another thought was 02 sensor..

And yes i *always* run 98 in the car, mostly BP ultimate with the occasinal tank of optimax extreme (100) when i can find some..

good idea andrew, will see if i can track one down

Still, going to have to drive this thing for another week at least like this.. unless it randomly fixes itself like its always done before!

[Konrad]

Update- checked the 02 sensor today, reads 0.2-0.9v when cruising, which i understand is normal. Disconnected it anyway which sends a constant 0.3v signal to the ecu- no effect.

Coolant level was normal, and the fresh oil i put in the car yesterday is at least still clean.

AlexR34- i know some manufacturers dont recommend ethanol but in my experience (aswell as many others) the car runs happier on it. These cars were designed to run on 100ron fuel after all. Some people have had problems with it though, in any case it would be on average 1 in every 10 tanks of fuel..

[AlexR34]

AlexR34- i know some manufacturers dont recommend ethanol but in my experience (aswell as many others) the car runs happier on it. These cars were designed to run on 100ron fuel after all. Some people have had problems with it though, in any case it would be on average 1 in every 10 tanks of fuel..

Yeah cool, i just thought id let u know what nissan told me.