crazy idle
 

ok, first of all I know I have posted about this problem before and I have tried different suggestions all to no avail. So please help me out again. I have an 87 SE, manual,with 255k and the idle is going anywhere from 400 to 1200...when it gets close to 400 it starts running really rough...as if it is trying to cut off but it never has. Also I should mention that this problem is more prevelant when the car is up to temp. I have had the car for about 3 months or so and this is still the one thing I cannot figure out. This is what I have done since I have owned the car: plugs, wires, coil, vacuum lines, cone air filter with adaptor plate, thermostat, radiator, AAV. This is a problem that has been getting worse...thats what leads me to believe that its some sort of sensor going bad....please someone help me out...I am going to race next weekend and I would like to look like a properly functioning slow car :)

you may want to check your connection to the head temperature sensor mine was causing me problems and the connection was only corroded. i was told it it not likely for the sensor itself to go bad but it can happen. try unpluging the sensor from the secondary harnass and see if the idle quits hunting.

can you give me an idea of where that sensor is? I dont have my manual with me today....thanks for the feedback I will try that....any more ideas?

Try changing your PCV valve. It is supposed to improve your idle. I helped mine a little.

Another shot in the dark might be that the catalytic converter is partially clogged. I'm thinking of changing mine just to see if my '88 picks up any pickup.

I already changed my PCV valve about a month ago with one from advanced auto...I have also done the alternator....and would a screwed up cat do that?....I was thinking about gutting my y pipe anyway....and I am not getting any rotten egg smell like my cat is screwed...you could be onto something, I dont know...thanks for the advice...keep it coming

I'm not sure that a new cat conv, or gutting your pipe would fix your problem, but I do know from past experience (on an old toyota) that a clogged CC can choke a motor and that it does get worse as it heats up.

G'luck...

ok thanks for the advice...I was talking to one of my friends that really knows subarus and he was saying possibly the TPS...what do you guys think would this cause this problem? Also if the cat is not rattling or smelly can it still be bad/clogged? Thanks.
Carson