Winter Blues

[LotusGTR]

So, I've got an R32 GTR and it's playing up a little in the colder weather. I thought it was tune related as there was a cold start problem, but Trent has given it more fuel and that problem has gone now. Essentailly the residual problem is now whilst the engine is cold and under light throttle it seems to miss or hestitate a little.....It might be 4th gear 60km/h even throttle. Always sorts its self out once warmed up. No problems under power.

Now it has new plugs, new coilpacks, -7s, Nistune and as Trent had it hooked up to the computer only late last week I'll assume all is well with the tune side of things. The engine is healthy as a recent compression test showed 165 across all cylinders.

Any thoughts as to what may be causing this?

Thanks.

[TiTAN]

could be the ECU pulling fuel out in closed loop and there is a cell thats not quite inline with the others and its a little lean, mine was doing this before, leans out going through/sitting on a particular cell and the ecu isnt fast enough to add fuel back in on closed loop and it splutters a bit as though its missing. once warm and out of warm up enrichment the problem went away.

does it always happen at the same revs with similar load?

[LotusGTR]

could be the ECU pulling fuel out in closed loop and there is a cell thats not quite inline with the others and its a little lean, mine was doing this before, leans out going through/sitting on a particular cell and the ecu isnt fast enough to add fuel back in on closed loop and it splutters a bit as though its missing. once warm and out of warm up enrichment the problem went away.

does it always happen at the same revs with similar load?

It's not that precise in terms of how it happens. Since the cold start issue has been resolved it starts nicely / normally and idles fine. Its after you've pulled away and given it a couple of gears and even out to a cruise that it starts. Yesterday was the worst it's been. I was driving home from work and it was about 10 degrees ambient. I have a short drive from my car spot to a set of lights and at the lights it nearly stalled. Idle was unhappy. Got going and it did it's stuttering thing until the temp gauge started to register. All was good from there.

So you're thinking it's tune related and not mechanical by the sounds of things.

[R31Nismoid]

Definately tune related IMO.

Won't be AFM's or anything by what you've described.

[R.3.2.G.T.R]

interesting, got my car back after a full tune yesterday however today on cold start, car stutters and hesitates until its warmed up

p.s my o2 sensors have been turned off due to incorrect voltage although doubt thats an issue

[Moodles2]

Could be the coolant temperature sensor at fault

[VB-]

^ yeah it will be in the cold start tune. o2 feedback is only used when at running temp

[LotusGTR]

Could be the coolant temperature sensor at fault

Could that be why my heater doesn't run full hot? I think you posted in my thread about that too.....

[Moodles2]

Could that be why my heater doesn't run full hot? I think you posted in my thread about that too.....

Different issue, the coolant temp switch is responsible for reporting the coolant temp to the ECU, if faulty it might be reporting the engine is fully warmed up when it isn't

[R.3.2.G.T.R]

^ yeah it will be in the cold start tune. o2 feedback is only used when at running temp

mine was tuned at UniGroup by Yavuz and he confirmed car is left on dyno overnight so he can tune for cold start the next morning, anyways, he will look at it for me soon and will report back what the issue was

[LotusGTR]

mine was tuned at UniGroup by Yavuz and he confirmed car is left on dyno overnight so he can tune for cold start the next morning, anyways, he will look at it for me soon and will report back what the issue was

Well, mine was left overnight too. Twas 4 degrees and it was looked at stone cold, first thing in the morn.