weird Jerking problem... Help???

[SubyFusion]

i have a 1992 legacy ss 5mt N/A and i have a weird problem! when im driving freeway speeds its fine but when i hit stop and go traffic my car jerks when i let off the gas and when i go to accelerate it jerks again like the clutch isn't grabbing but it feels like the engine. so im confused any help would be vary appreciated thanks

[Mattheww044]

the SS is the turbo version of the legacy... is yours the turbo or N/A?

[SubyFusion]

sorry i meant S as in sedan its an N/A thanks for the reply i am new here so any info on the problem would be greatly appreciated =)

[SubiePrice88]

hmmm...you wouldnt happen to have a Check Engine light on?

[Mattheww044]

oh ok, just wanted to get that cleared up. Yea as SubiePrice88 said, do you know how to check your codes?

[86ruguy]

mine's doin the same thing. and i have no CEL on.

[SubyFusion]

yes the check engine light comes on but its weird because it only comes on when i hit stop and go traffic and then when i get back up to freeway speeds it goes away.... and i tried to test 4 it but i cant because it disappears. When i am speeding up and slowing down a lot the light will come on and then the car seems to jerk like its engaging the clutch when i hit the gas or something witch doesn't make sense because thats not possible but thats what it feels like it also happens when i slow down its like a bucking kind motion. so i hope that helps any info??? thanks= )

[SubiePrice88]

Here is how to check the codes and clear them: http://www.surrealmirage.com/subaru/engine.html

[SubyFusion]

well that would help if the code stays but it goes away= ( it sucks i was driving today and i hit traffic and bam the CEL goes and when i slow down and speed up it jerks like crazy! i was having some problems with the Knock censer a while back but i put a new one in and cleared the ECU! i was thinking it could be the KS again but its not throwing the code and i don't think it would cause that kind problem it seems like it has something to do with the throttle maby??? not sure so i am still stuck any any more info on the problem...thanks

[SubiePrice88]

what do you mean by the code goes away?

[SubyFusion]

ok so originally it wasn't showing any codes when i checked the memory so i thought it wasn't storing it in the memory but now its showing a code 42 witch is the Idle Switch! thanks 4 the link SubiePrice88 = ) so now that i finally know what it is can any one give me some info on the problem???? dose this happen often? Thanks

[SubyFusion]

Is the IAC valve the same thing as the Idle switch???

[Legacy777]

No, the idle switch is built into the throttle position sensor.

[SubyFusion]

well the ECU is throwing a code 42 witch is the Idle switch, is there any way to fix it? i am not sure what to look for..

[Legacy777]

Test/adjust the Idle switch using these instructions.
http://www.main.experiencetherave.com/s ... sting3.jpg

If you still have the code, you may need to replace the throttle position sensor.