Another thing that I didn't mention in my last post was the method I use to adjust the throttle stop screw.
Firstly, because the idle motor is of the stepper variety, so the idle speed won't alter if you just unplug it. The only way to eliminate the motor's effect is to plug the airflow thru it.
I run the engine until it fully warmed up (at 90 degree plus) & then remove the air cleaner tube & plug the idle air channel with my finger. This is in neutral with everything else switched off.
The idle speed should drop around 100 rpm. If it drops too much or just stalls the idle stop screw should be adjusted up until you get that 100 rpm drop.
Obviously if it doesn't drop the idle stop screw is set too high. Adjust it downwards.
If you have access to a scanner the idle motor "steps setting" should be around 20 to 30, Ideally 25.
Dr Terry
Thanks guys,
played around with a lot of this over the last couple weeks. Terry, first things first, I replaced the IAC. Then did the idle reset (disconnect battery for a min, reconnect then warm up and hold revs at >2500RPM). Worked like a dream! Idle sat dead on 500-450RPM in whatever gear. Still a little bit of lurching but no biggie, can barely hear the IAC.
Went inside smiling. Came out and started it the next day, back to square one! (even after warming up). So I did the IAC block with my finger and set the idle screw, sounds just perfect with no IAC. Then in this process, I had my thumb on it for a good minute, the car dropped the idle down to the previously described RPM and all was well. Turn off, start again, back to bloody 900+RPM! the IAC is deafening and with my foot on the brakes, it literally does a little wheelspin as it drops into gear.
To answer your question, the engine does have a 'baby' camshaft (can't currently find specs) and supposedly a chip to suit (was told it was an 'SV500' chip), I have had all the best intentions on getting it tuned but was hoping to get it nice and driveable, club regoed and some headers before I dropped money on that.
I don't know a lot about htese AC Delco units but I wonder how hard it would be to reduce this idle stepper setting as it seems to be purely a computer problem, atm it's tempting just to plug the IAC port, seeing as I have literally no accessories.
Thanks again!