Rough Idle When Cold

[kezza_005]

Hi everyone.

I have a R33 GTST basically stock.

It does have a z32 AFM though.

PROBLEM:

Every morning when it's cold i start the car, it idles very rough and I even need to tap the accelerator so that it doesn't stall. When the oil pressure gauge starts to move the idle then stabilizes but it will missfire if I try to drive it. But when the water temp starts to rise it is ok to drive taking it very easy because it does missfire or something like that a little. When the water temp and the oil pressure get to opperating temps the car then drives like a dream perfect idle no problem with boost and does not missfire at all. It has been doing it for a couple of weeks now.

POSSIBLE SOLUTIONS I THOUGHT:

I have changed the plugs and the coils

Replaced the fuel filter

The AFM is brand new only a month old so I think thats fine

I cleaned the AAC about two months ago is shouldn't need cleaning again.

If anyone has any thoughts as to what else I need to check please let me know I can't seem to find anything else on this site as they are all about rough idle or missfire when the car is hot while mine only does it when it's cold.

Thanks Kezza

[GTR-N1]

The gap on your plugs is?

No unusual smoke or splutter coming out of the exhaust?

No sound of hose leaks?

[DVS JEZ]

so it has a Z32 AFM installed, is the ecu tuned to suit the Z32? what ecu are you running?

[kezza_005]

The plugs are gapped to 8mm.

There is no unusual smoke coming out the back.

I have had a listen for hose leaks and can't find any.

It has a stock ECU and the Z32 AFM hasn't been tuned,

as I was told by my mechanic that the stock ECU doesn't need to be tuned it just automatically learns that it has it installed.

When the AFM was first installed the car ran fine.

[DVS JEZ]

The Z32 tune will be off. It will run the car for a little while but the mixtures will be off. They have a totally different Voltage Quantifier map compared to the stock afm.

U need to either get a NIStune board and tune it

To suit z32 afm or get a stock afm and put it back in.

How long has it been running for with Z32?

[kezza_005]

It has had the Z32 for about a month.

My car wouldn't start this morning, dead battery getting a new one tomorrow and will see how it goes after that.

But does running a Z32 with the stock ECU do much damage to the car and can the ECU be tuned to suit the AFM.

[DVS JEZ]

It will run as u know." Shouldnt" hurt anything but the AFR's and timing look up tables in the maps will be different to a stock afm, as the afm is what the ecu uses to calculate load on the engine.

To tune for the Z32 afm u will need a tuneable ecu such as a NIStune or power FC.

[kezza_005]

I think there might be a little coolant getting into the block somewhere as I am loosing a little and there is white smoke

coming out of the exhaust.

Does anyone know if that would have anything to do with it.

[wedge_r34gtr]

I think there might be a little coolant getting into the block somewhere as I am loosing a little and there is white smoke

coming out of the exhaust.

Does anyone know if that would have anything to do with it.

Could be contributing to the problem.

But jez pointed out the main factor that needs to get fixed.

[DVS JEZ]

It may be a head gasket issue aswell.

How hard have u been driving while u have had the z32 afm fitted? Hopefully it hasnt been detonating

[kezza_005]

I don't drive it too hard at all maybe sometimes to 6000 RPM but thats not very often. But I will look into that.

[Moodles2]

Re-read what DEV JEZ has written, then read it again. Solution, sell the Z32 AFM, you DON'T need it. Replace stock AFM with the money. Or else you could keep going as you are now and blow up your motor (which I guarantee WILL happen).

A wrecker-spec RB25DET will cost approx 3k (at a rough guess), then there's the labour of putting it in.

But please when you do blow up that motor, please post the result in: http://www.skylinesaustralia.com/forums/topic/46581-report-that-engine-failure/