I have recently purchased a 94 R33 GTST, Manual. Has a blow off valve fitted, stock ECU, turbo upgrade (I Believe). I have had it for two weeks however I noticed that after driving it for a while, the RPM at idle would start dropping from 800 slowly overtime down to 500 where it would start hunting between 500-700. So this Saturday just for a laugh I decided to disconnect the TPS when the car was idling.
After I disconnected it, the engine became a little upset and started hunting wildly, so i thought I had found the problem and as such i cleaned the AAC valve (before i found out there was a tutorial on here, although i did it in much the same way). That seemed to fix the oproblem a little bit, however it still hunts occasionally, and when you turn the Aircon on, it destabilises, behaves almost like a critically under damped sinusiod, i.e. it takes it a long time to settle, sometimes it doesn't.
Also found that the AFM has been changed on this moddel as the connecter seems to have been spliced baddly (I am a particular fan of poor workmanship) into the loom. I found that out when I pinched the connection the engine stalled, so i have re-spliced the connections to the AFM and it seems to be fine now. Though it still hunts when it feels like it.
Also when I played around with the AAC valve and readjusted the idle, there seemed to be little change in RPM, except that one position made it more stable than any other (between 750-780RPM). So is the idle screw an Idle adjust or are you adjusting the gain in a Proportional-Integral loop for idle control?
I will clean the AFM in the comming week, could it be the TPS, if so what is the quickest way to adjust the TPS?
Any help and comments would be greatly appreciated, thank you.
P.S. On a side note, does anyone have any experience in dealing with Osborne Motors in Perth? I am looking for a good mechanic in that area. I have had a look, not the most glamorous of places however they are a Nissan Certified Mechanic (can do Nissan log book services), are members of MTAWA and are autherised serv group members. When I talked to them they claim to be quiet comfortable in servicing Skylines (of course they would claim that). However I did see them reconditioning two RB25DETs. Any comments would be greatly welcomed.
Thank You all.