s13 idle problem, already tried everything

[TLlew]

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 3500rpm 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.

[TLlew]

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.

[KiLLeR2001]

Replace coolant temperature sensor, then see how she idles.

Coolant Temperature Sensor | 1993 Nissan/Datsun 240SX 4 Cylinders M 2.4L SFI DOHC | AutoZone.com (http://www.autozone.com/autozone/parts/1993-Nissan-Datsun-240SX/Coolant-Temperature-Sensor/_/N-j22j9Z9gslt)

[TLlew]

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.

[rb240sxt]

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.

Mine with a rb20 is doing about the same thing besides the idle prob. My ecu says code 12. Check voltage from signal wire at the maf plug. Should be .5v with ignition on and 5 v idling. If not 5v replace the maf. Also when adjusting the tps were u doing it by sound or voltage?

[TLlew]

Mine with a rb20 is doing about the same thing besides the idle prob. My ecu says code 12. Check voltage from signal wire at the maf plug. Should be .5v with ignition on and 5 v idling. If not 5v replace the maf. Also when adjusting the tps were u doing it by sound or voltage?

I was adjusting my tps by voltage

[TLlew]

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.

[562s13]

also check your pcv valve and plug wires. and might want to replace pcv hose.

[fukusdm01]

Hey TL, did you ever resolve your problem? I have the exact thing going on in my car except no ecu codes.

[TLlew]

All that I've been able to fix was the engine being hard to start and missing really badly. I had a clogged fuel filter and a bad fuel line in the gas tank, so I was only getting 20 psi of fuel pressure. Still having all the other problems. Let me know if you have any luck fixing your car.

[Redmonkey]

Try checking fuel injector o-rings.