yes, spark timing set way advancd, is a problem, with too fast idle (in this case small part)
the surging, is the ECU hunting 800 rpm, it does that on all early, ECU, Not today, its very illegal. this bad act. surging.
the only other cause of surging is gross lean AFR, I'm sure you dont have that. if MAP is working.
but its the chicken and egg deal, (spark/RPM) all engines race if advanced too far. (and causes ISC to lose control )
yes, spark must be set , but if RPM is super high, the mechanical advancing weights in the DIZZY base will fly out and make setting it impossible.
800 is spec, RPM for spark setting,
Then , use a timing light (engines not static timed at assembly correctly) I crank engine sparks out.
and use timing light on a dead engine, set spark near 5deg, or so,. BTDC. (bingo, its set, static timed)
then start engine, and fix the air leaks.
you cant set exacting timing on any engine racing.... like that, and leaks.
but can with spark wires removed, cranking, (close but not perfect)
sorry you car don't have timing "freeze jumper" that is 91+ when ECU does all spark and timing advance.
full spec, timing, dizzy, even FSM pages, there,
http://www.fixkick.com/IGN_timing/89-timing.html
clean ISC
new gasket if other is cut wrong, or leaking, it needs 2 holes, not slots. for the air path.
coil 6 ohms.
can be tested with 12vdc battery, 1second on, rest it for 15sec, repeat, dont power it to 12vdc for long it will get hot.
btw the 500 is normal, if the iSC is closed.(or gasket blocked)
all G16s do that, (approx)
2500 is , 2000 rpm worth of air leaks (to the plenum)
the ISC is bad, in some way... you proved it.
here is the scope view
if the signal sticks to 12v full time, it overheats and races.
http://www.fixkick.com/IDLE-AIR/iac-wave1w.jpg
the surging, is the ECU hunting 800 rpm, it does that on all early, ECU, Not today, its very illegal. this bad act. surging.
the only other cause of surging is gross lean AFR, I'm sure you dont have that. if MAP is working.
but its the chicken and egg deal, (spark/RPM) all engines race if advanced too far. (and causes ISC to lose control )
yes, spark must be set , but if RPM is super high, the mechanical advancing weights in the DIZZY base will fly out and make setting it impossible.
800 is spec, RPM for spark setting,
Then , use a timing light (engines not static timed at assembly correctly) I crank engine sparks out.
and use timing light on a dead engine, set spark near 5deg, or so,. BTDC. (bingo, its set, static timed)
then start engine, and fix the air leaks.
you cant set exacting timing on any engine racing.... like that, and leaks.
but can with spark wires removed, cranking, (close but not perfect)
sorry you car don't have timing "freeze jumper" that is 91+ when ECU does all spark and timing advance.
full spec, timing, dizzy, even FSM pages, there,
http://www.fixkick.com/IGN_timing/89-timing.html
clean ISC
new gasket if other is cut wrong, or leaking, it needs 2 holes, not slots. for the air path.
coil 6 ohms.
can be tested with 12vdc battery, 1second on, rest it for 15sec, repeat, dont power it to 12vdc for long it will get hot.
btw the 500 is normal, if the iSC is closed.(or gasket blocked)
all G16s do that, (approx)
2500 is , 2000 rpm worth of air leaks (to the plenum)
the ISC is bad, in some way... you proved it.
here is the scope view
if the signal sticks to 12v full time, it overheats and races.
http://www.fixkick.com/IDLE-AIR/iac-wave1w.jpg
http://www.fixkick.com