s13 idle problem, already tried everything

[91hatch240]

I have a 91 240 that I bought with an idle problem, assuming it would be an easy fix. The idle fluctuates between 1200 and 4000rpm and when I unplug the tps to adjust the idle, it stays right at 4000rpm. Adjusting the idle adjustment screw doesn't do anything. Previous owner converted from auto to stick, if that makes any difference.

here's a list of everything I have tried so far:
-disassembled and cleaned iacv
-replaced and adjusted tps sensor
-replaced almost every vacuum line, except for the ones for the pcv valve
-added an extra ground
-unplugged the maf sensor to see if that was the problem, idle still surged
-pinched the hose going from the iacv to the air regulator, to test air reg., no change
-ran ecu codes, came up with a 12- air flow meter circuit and 13- engine temperature sensor circuit

I'm out of ideas and can't seem to find anything else on any of the forums, so any advice would be greatly appreciated.

[nismotuner1]

Fix your maf and coolant temp sensor. Not the sending unit for the gage but the sensor for the ecu. And it sounds like you have a massive vacuum leak.

[91hatch240]

I was working on the car today and it seems like there was a bad connection with the tps sensor. I fixed that and now the idle is bouncing between 1500 and 2000, and when I unplug the tps its still staying right at 4000 rpm.

[moso]

Fix your maf and coolant temp sensor. Not the sending unit for the gage but the sensor for the ecu. And it sounds like you have a massive vacuum leak.

he is right on, check out the maf, and the 2 wire temp sensor. either that or your wiring harness has a short.

[Shadow Drifter]

The plugs on both conectors should be sprayed out with MAF cleaner then add a little circut gress to it and you should be fine

[MR.chris]

I am having the exact problem that you are having, but I could not fix it so my car is at a local shop right now. LOL

[91hatch240]

Cleaned the maf and replaced the coolant temp sensor. Didn't change how its running, but now I'm not getting any ecu codes. I did check the timing, which was WAY off and now my car has some new problems.

- hard to start when and a bad miss (had those problems before)
- w/ the tps disconnected, can't adjust the idle rpm lower than 3000rpm and when I plug the tps back up it idles at 750rpm until it warms up then it idles between 1100 and 1600 rpm.
- until the car warms up it has almost no power below 2500 rpm, probably because the engine's missing so bad
- when i go drive up hill, it won't rev past 1500rpm and won't go any faster than 10mph
- also sometimes while driving the car won't rev any higher (had it happen at different rpms) and if I floor it the rpm very slowly creeps up

If anyone has any more tips I'd really appreciate 'em.

[91hatch240]

I was wondering if the distributor could be installed incorrectly. It has paint marks on it like it came from a junk yard and whoever installed it didn't bother to check the timing afterwords, so its hard to say if they knew what they were doing.

[turbonxsx]

When i have these problems I always resort to my Consult port connector and laptop to figure out whats what...