HOT ENGINE? CEL glows keyon, then goes out running? 1st........
ok , there are 2 issues, with idle.
900 is failed.
that means idle controls are out of control, does Head lamps on plus heater fan on and if defrost on , cause RPM to drop, that means no regulation, ECU can't control it.
The ecu does drop idle controls in failsafe mode or backup mode. (can)
http://www.fixkick.com/ECU/LimpHome/failsafe.html
16v is the harder one (air density system is...), and non OBD2 , x2 harder, no scan tools.
The 16v runs closed loop at idle, hot, all 16v do,
but how to tell that is very hard, near impossible. with no scan tool.
This ecu ,im told can even swing the 02 sensor, not in closed loop or even in fail safe mode, making this harder to diagnose.
on a newer car, im all over the scan tool looking at all live PID's (eg;oh look here, LTFT is dead its as is the 02 sensor)
For sure finding a dead 02, that is , it's stuck and not SWINGING, must be fixed first.
4 ways to tell that are. (any scope, DSO, fast smart DMM, or the very fine hacking tool
http://www.rhinopower.org/)
OBD1: horrors.
BLIND:101; (coolant is first)
Hot engine, must be 180F, or more or all tests useless. and holding.
one tests is to pinch the ISC air line (ISC is the electric idle control valve) it has 3 lines, 2 are hot water the cold line is AIR.
pinch the air line, what is RPM now. (400 and near stalling?) or stalls?
i always clean the ISC with the EGR, so the ISC is free,
see iSC video here,
http://www.fixkick.com/videos/FLV-all/showtime.html
it too must seal at least 90:% all old ISC leak a tiny bit, (rubber seal is beat up) but is not a problem if it mostly closes and opens fully.
what do is try to find out:
1: is ISC dead? or stuck open. coil check and cycle checked.
2: is ECU attempting to operate the ISC, if not its in failsafe mode,
to find that after pinching the ISC air hose, is to unplug the connector, this must give you 400rpm or very low, 600 ok too, but the pinched or unplugged, ISC must be way below 800 or the ECU can not gain control of it ever. see?
there are air leak issues,
if the metered air lines leak, idle speed rises (with prefect AFR ratios) (you)
if the un-metered air is leaked, idle drops, AFR goes lean, idle drops.
metered air leaks can be:
1: throttle plate blocked open with gunk there, or cables set tight, (3 cables with cruise, or 1 with 5sp and no cruise)
2: ISC leaks (needs to be recalibrate ask)
3: IAC leaks (its bad.) below throttle body, is this valve. closes at 150F.
4: some one fiddle the idle bleed screw and ISC lost control. this screw really is duty cycle calibrate. if really lazy (no scope or duty meter) some just screw it in to see if the ISC wakes
up and the ECU will then go to 800 all by its self.
if you had a scope or duty meter
you will see the ECU pulse modulate go to max , that is max time at 0v. 0v = closed ISC.
the ISC flutters 200 times second, and the time closes sets RPM right.
metered air means, MAF measure air.
good luck to you..
