[SPEEDR33PER]

hey ho everyone my problem is car has a missfire at idle on one cylinder,and runs lean all the time,when i put my foot down missfire clears and off it goes but still running lean.it also has slight stutter if not driving on full throttle, most off the componants have been swapped for known good units but cant seem to cure it,plugs are fine and coilpacks are ruled out as under load there is no missfire,tps has been swapped and icv cleaned again,coil amp swapped and other bits too,throttle response has improved dramatically and have had timing checked,fuel pressure checked and injectors cleaned so am i missing something? as i need it 100% for caning it round the ring so any help appreciated

ps its a 94 spec1 gts-t hks induction kit and in house aftermarket exhaust

 

[peterk]

tried swapping the AFM ?

 

[SPEEDR33PER]

been changed already mate and its a weird one as everything seems to be doing as it should just running lean.

 

[peterk]

check all the injectors are firing when engine is running.
(unplug one at a time and see if engine sound at tickover changes)

 

[For-Tune PVE]

Has the fuel filter been replaced, and if so, has the fuel pump been checked out/replaced yet?

 

[vizibledog]

Lambda???? Have you ran a diagnostic check on it yet?

 

[robrs2]

How do you know it running lean?

 

[Stusy]

A skyline running lean is a very bad thing

 

[SPEEDR33PER]

check all the injectors are firing when engine is running.
(unplug one at a time and see if engine sound at tickover changes)

good idea will do that tommorrow mate cheers

fuel filters been changed and i know the pump is ok as fuel pressure is spot on, lamda is switching fine and have had a diagnostic check on it, i have a a/f/r gauge on my car and it indicates running lean and when at dastek for rolling road i was told my car was running little lean.
and yep running lean is bad but got it back for tonight and it drives a helluva lot better and quicker than before it just misses and stutters at idle once above 1500rpm its off like a rocket.

 

[robrs2]

Does the a/f gauge swing from lean to rich or does it just stay on lean?

 

[SPEEDR33PER]

it didnt even register until i got on boost and after 3000rpm and on cruise it would go from lean to not even lighting up, tonite it goes from lean to rich and in between constantly after 1500rpm. so idle is my problem.

 

[For-Tune PVE]

From your description, would I be right in thinking this is a narrowband lambda gauge? What is the leanest value it reads to?

 

[For-Tune PVE]

it didnt even register until i got on boost and after 3000rpm and on cruise it would go from lean to not even lighting up

The reason I asked my question before is that at idle and cruising, engines will often be happy running leaner than 14:1, so if your gauge only reads as far as 12.5:1 for example, it would be worth checking it on a rolling road with an accurate wideband lambda sensor.

 

[cossiedave]

are all your connections nicely soldered, as a bad connection will give a false readind, which a/f device do you have ?

 

[NISFAN]

The reason I asked my question before is that at idle and cruising, engines will often be happy running leaner than 14:1, so if your gauge only reads as far as 12.5:1 for example, it would be worth checking it on a rolling road with an accurate wideband lambda sensor.

That would be rich, lean by definition is anything over 14.7:1 on Petrol.

What device are you using to determine how lean your engine is running. Is it a wideband (5Volts) or narrowband (1Volt) sensor?

What values are you seeing?

 

[For-Tune PVE]

That would be rich, lean by definition is anything over 14.7:1 on Petrol.

I wasn't saying otherwise Leaner than 14:1 = more lean than 14:1, i.e. higher AFR than 14:1. I haven't heard any mention of AFRs in question here, but if he can only "see" as lean as 12:1, it may appear that his engine's running dangerously lean when there is no problem at all.

 

[NISFAN]

No mate 12:1 is 'kin rich not lean, lean would be higher than 14.7:1, so in the 15's or 16's.

 

[For-Tune PVE]

I know that, but I still don't know yet what our troubled Skyline driver is seeing, or even what his gauge will let him see! Am waiting for some numbers

 

[SPEEDR33PER]

unfortunately its an led lit narrow band a/f/r gauge it doesnt say what its at just, red dangerous yellow cruising and green batter hell out of it,i have had it at a rolling road day and if i can read the sheet right, the graphshows 16 under 2000 rpm dropping to above 12 at 7000rpm if that makes sense as it was a dastek r/r. it was commented that the car was running slightly lean then in april and the fault was there as it is now.i have had it at checked again and been told it is running very lean. but it seems to coincide with my idle problem? hope this helps and thanks for your help so far:cheers:

 

[NISFAN]

A narrowband is almost useless, it only reads aprox. +-0.5 range around stoich. But yes 16 is a little lean.

I would think you have an air leak in the manifold, or bov.