Jacob Butler

So i have replaced almost everything i can think of that could be causing this. My next step is probably take off the intake manifold, replace all the gaskets, replace all cracked hoses and what not, and spray all the 200,000 miles worth of carbon buildup out. But before i do that i want to see if anyone has any suggestions of what else it could be. I will also be replacing the ecu after the intake manifold gaskets because the dealer wants 5x what its worth.
What I've replaced:
air filter
maf
i cleaned throttle plate to make sure carbon isn't keeping it from closing all the way
pcv valve
spark plugs
fuel filter
spark plug wires
cap
rotor
distributor
tps
made sure the coolant is bled
checked all fuses and relays
checked/cleaned all grounds
i cleaned the iacv really good. I would replace it but i can't find one for a 1990 ka24e
i sprayed carb cleaner all the hoses and gaskets i could reach without manifold off. no leaks
ign coil
igniter
wiring harness
The ignition timing is slightly off after distributor replacement but it idles the same as when the timing was correct. I can't time it because when i unplug the tps there is no change, idle still fluctuates 700-1000 rpm. Also the idle adjustment screw does absolutely nothing. I have searched for bad idle and thats how i found out all this other stuff to replace. I have also looked through everything the fsm says could be causing this. So basically when cold starting you have to give full throttle after it starts firing to get it around 1400 rpm. It starts up fine after warmed up. It will idle at 1400 when cold but still has small fluctuation. It drops to 700-1000 when warm and still fluctuates. Sometimes it wont idle at all when cold. If you raise to 1500 rpm idle starts surging up and down like crazy. Other times if you slowly raise rpm when it hits 1500 it jumps right to 2000.
Any help is appreciated. thanks

Jacob Butler

oh yeah the cts and the thermostat have also been replaced. The ecu codes only read intake air temp sensor because i have a pod filter.

mr.nismo.

Do you till have the AIV on it (valve that injects fresh air into the exhaust to warm up the CAT quicker). They're know for going bad (my personal E had the same issue). Basically the valve gets stuck open, and allows fresh exhaust gasses to get sucked into the intake stream. Fucks the maf up and the fuel mixture. Otherwise your actual egr may be getting stuck open as well. Youd notice it more towards idle ( egr should be closed at all times)

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Jacob Butler

Thank you for the suggestions. The aiv has been deleted. I also plan to just delete the egr if I end up pulling the manifold that way I can rule out that possibility.

Jacob Butler

Update: I managed to set the timing pretty spot on by messing with the throttle plate. Now the car idles at like 1500 and now I can hear a vacuum leak whistling but I can't find it. Manifold time.

mr.nismo.

What? You set timing moving the distributor, not the tps

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Jacob Butler

I understand, I didn't move the tps. I meant that I had to close the throttle plate a little more to even get close to 750 rpm so I could look at timing. Distributor was to for retarded so I moved it clockwise a bit and know it's spot on 15 btdc. Sorry for misunderstanding.