Rb20 Annoying Problem

[bretto]

hey guys

got an annoying problem in my car. just wondering if there is anyway to find out whats wrong without replacing everything?

its got the problem like the low engine stalling thing but it has never stalled. ill come to a set of lights and the revs will drop to like 400rpm then go to like 1200rpm then drop again and just keep bouncing up and down untill itll stop and rest at about 900rpm and idle good. if i give the accelerator a slight tap it might help it stabilize quicker but its still annoying. also when i got a dyno done on it the tuner said he couldnt get it to lean out hgh up in the rev range it would have the same fuel mixture at like 6000rpm as it would at idle and was running bullshit rich. which he said was great for drifting but not so good if you want max power out of the setup

any help would be greatly appreciated.

cheers.....brett

[BH_SLO32]

bretto,

I assume its an R32 and it sounds similar to a problem I recently diagnosed on my brother-in-laws 32. He had an aftermarket O2 sensor installed which was the cause of his problems. I initially checked the O2 readings being received by the ecu and appeared to be fine but by disconnecting the O2 sensor when the revs dropped resulted in an almost immediate increase in revs. Plug it back in and the revs dropped. This was an intermittent problem but I'd suggest unplugging the O2 sensor when the car is playing up and monitor the result.

Not sure about the rich readings at 6000rpm as the O2 sensor shouldn't be used in the ecu logic at that rpm if under load from what I understand. I assume the tuner was monitoring the A/Fs with their own wideband O2 sensor and not the one in the car.

Try disconnecting the O2 sensor in the first instance when the car revs drop and see what happens.

Hope this helps

[bretto]

thanks for your reply,

the problem doesnt really hang around for long enough for me to do this. if i pull up at a set of lights the revs will drop right down the back up high then back to say 500rpm then just over a 1000. then maybe drop to 900 and stay there. it fixes itself in abut 20sec but it is just an annoying problem. once its stopped at 900rpm it will idle there all day long.

[Cubes]

The AAC valve is probably a little gummed up.

Idling at 900rpm is fairly high, when all sorted they should be around 650 to 700.

I find 650rpm in really cold weather with a high elec load alt volts drop to high 12's. Bumping idle up to 700rpm stops this.