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Discussion Starter #1
Hello guys!

I know that misfiring problem is a common thing, but i still can't fix it. Car simply won't go higher than 4 - 4.5k rpm and i hear popping sounds from exhaust, just like a bee-r rev limiter lol. It goes higher only with ~25-30% throttle. I tried to isolate coils, to change and regap plugs etc.

And now i have another problem - unstable idling. It's ok while car is cold, but when it's warm idle is waving from 800 to 2 500 rpm (up-down-up-down), sumetimes it's stable, but incredibly high (2500 - 3000). Maybe it's faulty (sticking) iac/aac or some ecu problems?
 

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Everybody knows that the bird is the word
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I tried to isolate coils, to change and regap plugs etc.
....and your findings were ...?
What mods does your car have?
What plugs did you fit and at what gap?
How did you try and isolate the coil packs? It should be very simple to find out what cylinder is missing and confirm a coil pack as a problem.


And now i have another problem - unstable idling. It's ok while car is cold, but when it's warm idle is waving from 800 to 2 500 rpm (up-down-up-down), sumetimes it's stable, but incredibly high (2500 - 3000). Maybe it's faulty (sticking) iac/aac or some ecu problems?
Based on the symptoms, either valve could be playing up (idle and cold start valves). I'm not 100% on this as I've never had to deal with it causing a problem... but also, AFM.
 

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Discussion Starter #3
....and your findings were ...?
What mods does your car have?
What plugs did you fit and at what gap?
How did you try and isolate the coil packs?
I found nothing... old plugs ok, nothing unusual, coils have some little scratches on their sides.
My car is almost stock except pod filter, FMIC, oil cooler and mishimoto radiator with pair of electric fans. Stock ECU, no safc, stock boost with stock 2-step solenoid.
New plugs - BCPR6-ES 0.8mm gap.
That's how coils were isolated:


Based on the symptoms, either valve could be playing up (idle and cold start valves). I'm not 100% on this as I've never had to deal with it causing a problem... but also, AFM.
My MAF is really strange... it's green, but my car is sept.95 and coils have no external ignitor, so i think i have s2 engine and there must be pink MAF. Could be mistake of previous owner? who knows... right now i'm looking for pink maf and wideband O2 sensor to make some tests and to be sure about air-fuel ratio.
 

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Madman Sometimes
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Hi mate i had the same problem on my r34 gtt it turned out to be the nvcs pulley was faulty, Not sure if your car has this though.
I have a pink maff for a r34 gtt will it fit yours again don't no. There is a test you can do again on the 34 get a piece of wire bridge the gap between certain plug points on the diagnostics plug, Can't remember the exact way to do it but it's a self diagnostic on the 34. Dont no if you can do it on a 33 type it into google thats where i found out about it someone on here may have a bit more info on it hope this helps cheers.
 

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I found nothing... old plugs ok, nothing unusual, coils have some little scratches on their sides.
My car is almost stock except pod filter, FMIC, oil cooler and mishimoto radiator with pair of electric fans. Stock ECU, no safc, stock boost with stock 2-step solenoid.
New plugs - BCPR6-ES 0.8mm gap.
Ahh spot on, those are the exact plugs I'd fit with those mods, they definitely shouldn't be the cause of your miss!
Does the engine misfire when you rev it in neutral? If so, it makes finding the cylinder that's missing much easier, otherwise you'll need to take it for a drive each time....
For arguments sake, lets say it misses in neutral - unplug #1 coil pack and rev the engine. If the miss is still the same, it's not that cylinder and plug it back in. Unplug #2 coil pack and rev the engine... (you can see where I'm going with this lol). Once you find one that alters the miss, you've found the faulty cylinder! Say it's #2 cylinder - swap #1 and #2 coil pack around and see if the problem follows the coil pack or stays with the cylinder.
But, there is still no guarantee it's a faulty coil pack but that's where I'd be focusing my attention first

Another option is a loose/dirty injector plug... I had the dreaded 4500rpm miss on my R32 and I instantly assumed coil packs... I did all the test I mentioned above and to my surprise they were all ok. I started looking toward the injectors and after playing with the plugs the miss disappeared. Luckily I didn't take it as far as removing injectors before spotting the problem



My MAF is really strange... it's green, but my car is sept.95 and coils have no external ignitor, so i think i have s2 engine and there must be pink MAF. Could be mistake of previous owner?
That is a bit bizarre! But I wouldn't pay too much attention to that... if the wrong AFM is fitted, the car will not run properly at all. The green and pink label AFMs can be swapped over fairly easily anyway (StuartTheFish has successfully done it) so maybe a previous owner had a faulty AFM and just used the only one he could find - a green one ...?
 

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i had the exact problem when i bought my r33 gtst i have the spec 1.5 it was missfiring very badly so bad it was popping back through the exhaust (standard) it blew the back box off i replace it with a 3" cat back system still the same i replaced the plug with the iridium ngk and replaced the coil packs with the red jacket ones. missfire totaly gone now. the coil packs arnt cheap but well worth the cost in my opinion mate. id start there first im running the pink afm on the 1995
hope this helps
 

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The idle issue could be an airleak or an iacv problem.

Is the misfire definitely a misfire where the car is spluttering, or is it just hesitation? Do you have access to consult? Do you know if your ignition timing is correct?

As for the afm, the green label and pink label afm's are identical in their operating range, so just having the "wrong" afm on your car won't cause any issues. As has been said, I'm using a pink label afm on my spec 1 with no problems, the only difference is the spec 2 afm doesn't need a chassis earth wire, and it has a plastic funnel around the hotwire. Both operate the same, and give the ecu the same readings.
 

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Discussion Starter #8
Does the engine misfire when you rev it in neutral? <...>
unplug #1 coil pack and rev the engine. If the miss is still the same, it's not that cylinder and plug it back in. Unplug #2 coil pack and rev the engine... (you can see where I'm going with this lol). <...>
Another option is a loose/dirty injector plug...
Nope, only misfire while driving, i.e. it misfires only when boost goes positive.
Didn't think about injectors... Thanks, that might help!

the coil packs arnt cheap but well worth the cost in my opinion mate. id start there first im running the pink afm on the 1995
hope this helps
Thanks! I'm thinking about splitfire now... if i wouldn't find any other way to fix misfire - i'll buy them.

The idle issue could be an airleak or an iacv problem.

Is the misfire definitely a misfire where the car is spluttering, or is it just hesitation? Do you have access to consult? Do you know if your ignition timing is correct?

As for the afm, the green label and pink label afm's are identical in their operating range, so just having the "wrong" afm on your car won't cause any issues. As has been said, I'm using a pink label afm on my spec 1 with no problems, the only difference is the spec 2 afm doesn't need a chassis earth wire, and it has a plastic funnel around the hotwire. Both operate the same, and give the ecu the same readings.
It's definitely a misfire - it just don't go higher than 4.5k rpm and black smoke (fuel) with flames goes from exhaust at 4.5k. Ignition is about 15deg, but i'm going to re-check it with strobe.

I heared that pink one is a little bit "wider", so they have a little bit different voltage/quantifier maps, e.g. if you have s1 ECU + pink afm - you'll get lean afr, if you have s2 ECU + green afm - you'll get rich afr, s1+green or s2+pink - ok (stoich afr). But if you say your car is ok then there may be no diference between green/pink afm...
 

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Discussion Starter #10
I guess i found the reason of bad idle...
That's my IAC...

No seal, no o-ring, just silicone sealant everywhere. Previous owner wasn't too kind to this car... :spank:
with increasing temperature sealant becomes softer and interfered with the valve. That's why valve get stuck yesterday...
There is definitely no difference mate, I got the same afr's with each afm.
Thanks mate, now i don't need to look for another afm. :cheers:
 

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Discussion Starter #11
I cleared AAC/IAC, installed it with new gasket and nothing... no stable idle at all... Engine goes from 1000 to 2500rpm. If i'm disconnecting IAC/AAC connector - nothing, still waving 1k-2.5k, but if i'm disconnecting throttle position sensor - idle become stable, but too high (~4000rpm). And another strange thing - my ECU has no diagnostic led on it. Is it ok?
 

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have you changed the coil packs yet?? the pic you showed has the rubber sleeves missing, like i said i had the misfire on positive boost changed my plugs and coil packs no more missfire. they are expensive mate but go for the red jacket ones you can get them off ebay for around £200 if you fish about. they are well worth the extra tho i got mine from japan worth the wait tho
 

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While I was trying different things to cure my misfire I took the idle valve solenoid off and without realising it a tiny spring fell out. When I put it back on, my idle had gone high (2000 rpm) and unstable. Mines a different looking idle valve to yours but might be worth checking. I put in a half a spring from a ball point pen and that fixed it.
 

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just gonna throw this in hear its poss your fuel pump is failing not putting up the fuel pressure i had this problem and a new walbro cured mine check fuel pressure
 

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Discussion Starter #16
While I was trying different things to cure my misfire I took the idle valve solenoid off and without realising it a tiny spring fell out. When I put it back on, my idle had gone high (2000 rpm) and unstable. Mines a different looking idle valve to yours but might be worth checking. I put in a half a spring from a ball point pen and that fixed it.
Nope, i still have spring inside... But thx anyway

just gonna throw this in hear its poss your fuel pump is failing not putting up the fuel pressure i had this problem and a new walbro cured mine check fuel pressure
Thx, i'll check my pump and pressure regulator.
 

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Discussion Starter #18
I fixed it!!!
High idle was because of my tb and tps.
1) TB was opened a little (~1mm)

After adjustment idle is around 900-1000rpm.
2) Looks like my tps is broken. There are 2 connectors on it. Upper is throttle switch (for idle judgement), lower is position sensor. With closed tb lower should give around 0.4~0.5v and ~4.5 on WOT. Upper should be shortened with closed tb (0 ohm resistance). I tried to align my sensor, but i can't get 0.4 with closed throttle. If i'm ajusting it to 0.4 then upper switch is opened (no idle). Max i can get for lower connector is 0.25-0.3v with upper connector closed (car on idle).
 

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i have a simular problem withe the tps on my r33. but mine wont idle. only four a few sec. then dies. kan you conferm if your tps is broken?
 
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