RB20det Tune Issues

[nj1]

Hi All,

 

Apologies for the long post.

 

Ever since having cams installed on my rb20det r32 skyline I have had consistent idle issues.

 

Car was initially built and tuned by Tuner 2 but I went to Tuner 1 as I changed address.

 

TUNER 1:

 

Did all the head work includings cams, camshafts, springs and tuned the car with new setup.

 

Initially the car's idle would hunt on cold start. The idle would bounce from basically stalling to 1300 rpm and stall. It would take 4 to 5 attempts to start the car.

 

After advice from this forum I took it to my usual Tuner (Tuner 2) to check the tune.

 

TUNER 2:

 

Reviewed the tune (done by Tuner 1) and said it was rubbish (car was essentially block tuned) and dyno tuned the car and fixed cold start and found more mid range power.

 

On cold start the car still hunts between 700 to 1200 rpm for about 15 seconds then settles down to approx 900 rpm. I can live with this as atleast the car starts now.

 

This all well and good except now when I drive and come to a complete stop with the clutch in the car idle hunts again and 90% of the time stalls.

 

So far 2 seperate tuners are having trouble getting the car to idle.

 

I am not sure what is causing the problem specifically. Any advice on what I should be telling the tuner or questions I should be asking to get the problem fixed?

 

For my info what causes the idle to hunt? Is the ecu controlling/cutting fuel on/off?

 

Any advice would be much appreciated.

 

 

[R_34]

Clean the idle valve at first. It's located at the rear of the intake manifold. Once cleaned you may need to set the idle again but it should solve your problem.

[zoomzoom]

What ECU, do you have a wideband etc? Do you have the ability to access and change the timing and fuel maps yourself?

A couple of things spring to mind with a tune: 1) inconsistent and overly retarded timing in the idle load cells. 2) inconsistent and/or oscillating afrs in the idle load cells. Lean spots and retarded timing will prevent the engine from settling into a steady idle. The auxiliary air controller can start oscillating to prevent a stall, which then interacts with the above issues. Without measurements, its only a guess.

[nj1]

Link g4 ecu.

I will get it back in the shop and they can have a look at idle control valve and clean it out.

[Wheezy]

Are both the AAC and IAC still in use?

My 20 hunted on cold start until I refitted the cold start valve.

I thought it was the aftermarket plenum, but once I had all the factory sensors back and wired it was like factory.

[Dose Pipe Sutututu]

Add more timing on idle, and richen those load points. Also PID and the base duty table for idle may require more work.

Should take a competent tuner all of 15 minutes.