R34 Gt - Splutter/missfire On Light Throttle?

[Silver_GT]

I've got a problem with my GT which ive had since i bought it, but it was never on the top of my list of things to do, but now it is lol.

under light throttle every now again I get what feels like a heavy missfire, not constantly, just a jolt every now and again sometimes it worse than others but its definantly always there, When i first got it i checked the ecu codes, it showed up 02 sensor code, so obviously i thought this was problem, i reset the codes, took it for a drive and then the 02 code came back, so i replaced the sensor, but i still have this problem, but the 02 sensor code hasnt come back, so it must have been completely unrelated althought i sometimes got the CEL coming on at the same time as the miss? Definantly didnt get any other codes besides 02 sensor (Double Confirmed with Consult) and im Definantly No Longer getting it.

Car Runs and idles fine, acceleration is fine and appears to rev to redline freely (maybe a bit slower than it should but thats coz its missing a turbo lol)

So throw some ideas at me? Doesnt seem like an afm problem does it? Maybe has the Dry Solder Joints problem? Or am i going to have to buy some coils? Its just when i changed my plugs the coils looked brand new, but i suppose not alot of dirt would get down there?

Edited February 8, 2009 by Silver_GT

[cosmic starz]

I've got a problem with my GT which ive had since i bought it, but it was never on the top of my list of things to do, but now it is lol.

under light throttle every now again I get what feels like a heavy missfire, not constantly, just a jolt every now and again sometimes it worse than others but its definantly always there, When i first got it i checked the ecu codes, it showed up 02 sensor code, so obviously i thought this was problem, i reset the codes, took it for a drive and then the 02 code came back, so i replaced the sensor, but i still have this problem, but the 02 sensor code hasnt come back, so it must have been completely unrelated althought i sometimes got the CEL coming on at the same time as the miss? Definantly didnt get any other codes besides 02 sensor (Double Confirmed with Consult) and im Definantly No Longer getting it.

Car Runs and idles fine, acceleration is fine and appears to rev to redline freely (maybe a bit slower than it should but thats coz its missing a turbo lol)

So throw some ideas at me? Doesnt seem like an afm problem does it? Maybe has the Dry Solder Joints problem? Or am i going to have to buy some coils? Its just when i changed my plugs the coils looked brand new, but i suppose not alot of dirt would get down there?

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Unless you have Code 21 do not waste any time thinking about the coils - they must be OK - maybe you need to replace the fuel pump or fuel filter is clogged - look at the R34 Engine Service manual for clues to fix your specific symptoms - they are all listed there.

[Silver_GT]

finally got off my ass and ran a few tests, first thing i check was the tps adjustment, it was out by 0.2 volts (was at 0.2, supposed to be at 0.4 with closed throttle) and its now PERFECT that i have adjusted it, it was something i originally thought "wouldnt have been touched so i wont bother checking" silly me! Throttle response is now completely smooth with no "jerkiness"

[Silver_GT]

ok so after driving to and from work today, the problem is still there, but only very slightly and its nowhere near as violent, all signs point to me not adjusting the tps accurately enough, does anyone know if its supposed to be done with the engine cold (as heat generally creates more resistance, and the tps being a varistor, heat may alter its readings?)

[vinnie32GTS4]

have you checked your AFM....this was happening with me and i changed mine and now the problem is gone.

[Silver_GT]

That was my next port of call, was yours only giving you issues at very light throttle? My TPS is adjusted 100% to where it should be, and it still doing it, but only very very slightly, and i can more hear it than feel it.

[hotchoc]

wat's tps if you dun mind me asking ?

sds a bit like my case: http://www.skylinesaustralia.com/forums/Ca...ti-t255975.html

[Silver_GT]

tps = throttle position sensor, its on the side of your throttle body, sticking the multimeter probes in the back of the plug on the top and middle pins, you should get 0.4 volts with the throttle closed.

[Wacky Dee]

http://www.skylinesaustralia.com/forums/Ca...tt-t256128.html

my car was missing on idle and light throttle when new sparkplugs gapped to 0.7mm were put in .. regapped to 1.0mm and problem was solved.

[vinnie32GTS4]

That was my next port of call, was yours only giving you issues at very light throttle? My TPS is adjusted 100% to where it should be, and it still doing it, but only very very slightly, and i can more hear it than feel it.

yep thats right...changing it fixed it...however it then sorta came back and i disconected my O2 sensor and now it runs a dream..just gota get a new O2 sensor now.

[Silver_GT]

Just to end this guys for somebodys future reference, it was the AFM (Will be confirmed monday when mine comes in the mail) But i disconnected it and started the car up, usually if i hold the revs at 1500 it would splutter every few seconds, with the afm disconnected it does not, seems to be it!

[gotRICE?]

Just to end this guys for somebodys future reference, it was the AFM (Will be confirmed monday when mine comes in the mail) But i disconnected it and started the car up, usually if i hold the revs at 1500 it would splutter every few seconds, with the afm disconnected it does not, seems to be it!

Only problem with that is, the car will idle mint without an AFM, but as soon as you gve it any more revs it will cough and splutter even worse Not an ideal way to test it. lol.

You'd be better off borrowing someones AFM that you know works first. A friend of mine bought two second hand ones, and then a brand new one, a good $800 all up. Ended up being a faulty earth in the ECU Sucks to be him.

[Wacky Dee]

how the hell did he find out about the earth? Seriously sometimes the weirdness of skylines issues is a real worry and so depressing. How much does an OEM (don't have PFC so cant use z32) replacement AFM for an R34 GTT cost approx. ?

[Silver_GT]

It'll rev up to around 2200rpm fine without the afm generally, good enough test for me bought a 2nd handy anyway, we'll see how it goes, pretty confident tho. No idea what a new one is worth, problem like $500

[gotRICE?]

how the hell did he find out about the earth? Seriously sometimes the weirdness of skylines issues is a real worry and so depressing. How much does an OEM (don't have PFC so cant use z32) replacement AFM for an R34 GTT cost approx. ?

lol. I think it was around $600 NZD from RHD Japan. Expensive paper weight huh. Wont be able to recoop that cost easy.

In the end it was getting so frustrating he took it to an auto sparky who found the bad earth in an hour or so. He had just returned his car to stock from an HKS turbo kit/z32/pfc etc.

Im guessing it may have gotten damaged in storage. Bummer