My suby is a 91 Legacy L Wagon and the past couple weeks its been having a lot of problems.
Runs fine when first started/cold but when the engine gets to operating temp it starts having trouble and throwing codes.

Problems are:
Idles at 400 (idles at a normal 900ish when cold)
Idle will randomly surge from 200-1000 over and over and will want to die
Very sluggish under 3k rpm

The codes thrown are:
11 crank angle sensor

22 Abnormal voltage produced in knock sensor monitor circuit

24 Air control valve inoperative (Abnormal signal produced in monitor circuit)

31 Abnormal voltage input entered from throttle sensor

32 Oxygen sensor inoperative

35 Solenoid valve inoperative

Any idea what the problem could be? Possible fixes?

definitely check the timing belt.

 

check battery/cables/ground connections and charging circuit.

 

check for vacuum leaks

 

(start with the above - if no improvement try the next items)

 

consider cleaning the IAC valve.

 

consider a new knock sensor.

That's a lot of codes, first 3 steps are:
 

1. clear codes and see which one comes back first - read it immediately when the check engine light comes on.

2. check and clean/tighten battery terminals/clamps - low voltage may be making dirty signals.

3. check voltage at the battery with engine running. the codes may be an artifact of the low rpms/low alternator output

 

clean idle air controller.  best to remove it and clean it, but sometimes you can blow cleaner into them insitu.

 

knock sensors often crack at the base.  replace them with a $14 ebay knock sensor.

 

questions:

how long have you owned the car?

was it working perfectly find before this - amazing performance, gas mileage, and history?

how many miles are on it?

Edited July 9, 201411 yr by grossgary

were you doing any work under the dash just before this started giving you trouble?

did you or someone else connect the green test connectors under the dash?

Cleared the codes and drove around for a while. CEL didnt come on, but still had the same problems. Ive had the car about 8 months and its been running great up until now. It has 170,000 on it

how long was the CEL on before you checked the codes?

 

I would start with a new knock sensor, and possibly the O2 sensor, and see what happens, what codes come back...

 

Knock sensor will cause the ECU to alter fuel & timing advance, which could be the cause of some of those other codes.

O2 sensor will also cause driveability issues.

not too long, i drove around again today and the only code that showed up again was 35. I am going to clean the iac and report back