idle quality

[TTT]

I have the following.

Silver top RB20DET

RB25 turbo

TRUST panel filter

New NGK copper plugs (gapped to 0.8mm)

Coils are perfect

3" turbo back exhaust.

100K km service completed with usual changes (belts and water pump etc...)

However, I still have a slight pop at idle.

and the revs will rise and fall up to about 200rpm, like surge between 700-900rpm.

I've been in other RB20DET powered cars and I don't see that with them.

What else can I check.??

The AFM is clean.

There are no leaks or holes in hoses or pipes.

The car revs fine.

Gets to red line and runs 13psi boost no problems, no hick ups, no misses or back fires...

Fuel mixtures are about 12.5:1 under full load at about 4000rpm

Still running standard BOV..

It's nothing major but I'm just curious as to what else would cause a slightly rough idle...

any help would be appreciated..

[Roy]

What is your water/coolant temp, is it possible the thermo fan is switching on/off?

[TTT]

this is at normal operating temps.. the gauge shows right in the middle..

what ever that is..

My thermo does not run.

At the moment, it is connected to run only when the air con is on. ( I will be getting this changed soon)

the radiator is a twin core and is only slightly wider and taller than standard.

The only cooling fan is the Clutch FAN.

I keep hearing about some sensor at the back of the Plenum.

Can't remember the name or what it does or how to adjust or clean it..