[dragonsteel12]

Haven't posted for a while but I'm having issues with my idle.
The car is a 91 dohc (non turbo)

Some of the symptoms its having include,
-car is running rich,
-car backfires/pops a decent amount when you blip it very lightly on decel, it doesn't sound bad at all and at first it seems like a burnt valve or something, however my car has been surprisingly loud recently and I wouldn't doubt its an exhaust leak before the cat.
-car runs completely fine, revs to 6500 pinning it no problem, when you blip the throttle very lightly at idle the car will drop to 2-300rpm then bounce back up. When its cold it will stall. it also does this when you floor the clutch while driving, although it has never stalled while driving.
-the car also jerks when you take your foot off the pedal in first, not sure if this is related.

I have recently changed my isc to eliminate this problem but it did not fix it.
my spark plugs look fine. electronics replaced includes; spark plug wires, ptu, isc, coil packs, ecu was rebuilt about a year ago.
the car raises idle for ac, power steering, headlights etc like its supposed to but the drop in idle becomes much more apparent when these systems are being used.

My next steps are replacing the o2 sensors, rebuilding injectors, checking for leaks in the intake system, possibly rebuilding throttle body.
Anything else I should check for and any ideas as to what this could be?

 

[mini_cal]

Didn't see it on the list of what you've inspected, but have you taken off the IAC by the intake to inspect for buildup of grime? Use some carb cleaner while the IAC is facing downwards to give it a clean if it's dirty. Mine was as black as my car's paint when I first pulled it 😆

 

[dragonsteel12]

Didn't see it on the list of what you've inspected, but have you taken off the IAC by the intake to inspect for buildup of grime? Use some carb cleaner while the IAC is facing downwards to give it a clean if it's dirty. Mine was as black as my car's paint when I first pulled it 😆

I cleaned the old iac pretty well before I decided to replace it, however I didn’t clean the inside of the throttle body cavity for the isc, I’ll try that tonight then see if it helps.

 

[PuckVader]

You might also check your MAF, swap in a proper one for your specific car and see if that helps, did with mine. You said you cleaned your iac, if you have a spare known good one, I'd try that as well as could be more than just dirty. Good luck !