I have having problems with a looping idle in my 90 legacy. This just started last weekend and I don't even know where to start. The first video is of the car cold and me not giving any gas at all.

 

cold idle

 

The second video is after it is warmed up, still a little loop, but not as bad.

 

warm idle

 

It came up after a rally cross last weekend. It had never done it before.

 

Any help would be great.

 

thanks

oh i should add too that it drives normal

I have having problems with a looping idle in my 90 legacy. This just started last weekend and I don't even know where to start. The first video[...]It came up after a rally cross last weekend.[...]

Sorry, old/slow computer, dial-up ISP, etc., so I haven't seen your video. However, idle lope (not "loop") can have a few causes, from the simple to the annoying/frustrating. I'd start by checking for loose vacuum hoses, then consider IAC and TPS. Loping can also be a characteristic of too much intake/exhaust valve overlap, so unfortunately a valve sticking is another possibility. (On a DOHC, a jumped belt can be the cause of excessive overlap.)

Vacuum or IAC it seems. Probably IAC because it's not so pronounced when the car is warm.

i don't think a vacuum leak, i did the old spray carb cleaner around under the hood to see if the idle goes up.

 

i think i got a IAC around i will see if i can swap it out in the next day or so.

What I fing interesting and very much surprising - but cannot make anything of - is seeing the tach needle fall to zero without the engine stopping.

What I fing interesting and very much surprising - but cannot make anything of - is seeing the tach needle fall to zero without the engine stopping.

It's mechanical - so the gauge may have been showing 0, but the engine was probably still going.