knfeparty

Recently started not dropping all the way down to idle. Really annoying when I try to slow the car with engine braking my lifting on the gas because it just maintains speed or sort of bucks as it slows down. Had this symptom before and after a recent O2 sensor install. I really need to get this fixed before the next AutoX on the first of April so advice is greatly appreciated.

Jon Moeller

Sticky throttle body? Or throttle cable?

genikz

Did your throttle return spring fall off?

BTW, you'll probably fail Auto-X tech inspection if your throttle doesn't return quickly when you lift. I just attended a PCA Auto-X and they specifically tested for that.

knfeparty

Yeah I know I autoX'd it this past weekend and the tech gave it a pluck to make sure it works! Maybe he broke it....

JustinL

Check to see if the throttle position switch is clicking. The throttle plate can close, but if it isn't detected, then the fuel isn't cut at higher rpms and it will idle at part throttle maps.

rberry951

+1 this is your problem

knfeparty

I can definitely hear it clicking. I've got a lot of experiences with microswitches gone bad from paintball, and it sounds like it is operating normally. Where is it exactly so I can check the connections?

sethclayton

It's located directly under the throttle body...you won't be able to hear it click from inside the car. You'll have to turn the throttle cam from under the hood and listen carefully. Not a loud click at all. Clark's Garage has a good write-up on how to test it... http://www.clarks-garage.com/shop-manual/fuel-06.htm

rberry951

It is inside the tps, I'm trying to find a wiring diagram, I forget which pins. Somebody will probably post one before I find one...

Clicking doesn't mean it is good, but that's a telltale behavior. But that behavior could be a couple of other things too now that I think of it, like the ICV can cause weird idle down issues like this. Will it ever idle down? Have you ever adjusted the physical throttle body stop?

knfeparty

Yeah, yeah I was moving the cam with my hand when I was listening for it. I'll go try and take a look right now...the area around the cam was pretty grimy too and I cleaned it up a bit, but the switch malfunction seems to be a likely culprit as well from what you guys have said and from what I'm experiencing when I drive.

knfeparty

I haven't touched the throttle stop although it was tempting to back it out when this thing started happening. It idles down just fine about 80% of the time, and when it doesn't a little blip on the gas usually brings it back down.

Rock

My 951 did this. Twas the ISV

knfeparty

I assume you guys are talking about the idle air control valve? I've seen pictures but I don't know where it is on the car. I'm going to check out that TPS before anything else though. I love how the explanations for the problem get more complicated / expensive as the thread moves on.

rberry951

If it is intermittent I suspect the idle switch even more, it's just not closing every time. You can loosen the two screws on the TPS and rotate it counter-clockwise just a hair and see if that makes it stop. In adjustment, it should click just as the throttle body reaches the close stop. But don't mess with that stop screw.

rberry951

Your tranny is bad, rip it out and buy a new one...