OK. I searched for a bit and didn't find anything similar to my problem, not saying it doesn't exist but i didn't see it.

A couple of days ago I ran some stuff through my intake to clear out all the buildup it had on it. It seemed to work really well. I let my car sit overnight and drove over 100miles the next day. The problem I had was the idle. If i was cruising for a while and take it out of gear the idle will stay at 2k rpms for a while. After sitting at a light or something for a while, the idle will slowly, very slowly, return to around 1000RPMs. I have seen that the most common cause for a fast idle is a vacuum leak. I can't find one so is there anything else that would cause this idle problem?

As I said, before I cleaned the intake the idle was fine at 1000-1200. I ran 2 cans of B-12 chemtool through the intake just to make sure that it was nice and clean as I noticed a lot of buildup. I sprayed most of it right through the throttlebodies but for some of it i took the vacuum line off of the FPR and sprayed it into the vacuum port.

Thanks for the help.

 

Without a "signature" (year, model, engine, trans, major mods) it really makes it hard to help you. For a stock engine 1,000-1,200 RPM is too high - 550RPM in gear/650RPM in neutral for an A4, 800RPM for an M6. The stock tach error might make an M6 appear to idle at 1,000RPM, but 1,200RPM is definitely too high. Appears you had a problem even before you poured "some stuff" into your intake. Now if your engine is modified, PCM has been reprogrammed, etc. it might have been idling right where the programmer set it.

See why its so hard for anyone to help you when you don't provide that basic info in your "signature"?

Which "vacuum line" did you take off, and did you verify you didn't crack it or not put it back on all the way?

Have you verified that the throttle blades are closing fully against the throttle stop screw?

 

I'm sorry for not saying earlier. I didn't mean to upset you.
My car is a 93 z28 M6 with LT4 conversion. It was "professionally" tuned on a dyno some time ago. The vacuum line that i took of was the line that goes to the FPR, the bottom one on the passenger side of the intake. I know i plugged it back in correctly because i can see the fuel pressure change on my fuel pressure gauge on my hood.

The product that I used was the first on this page: http://www.berrymanproducts.com/Default.aspx?tabid=138
Aerosol carb and choke cleaner.

The throttle mechanism does rest on the throttle stop screw on the BBK 58MM TB.

I do recall that right after we got the LT4 kit on, we had to adjust the position of the throttle stop screw because it wouldn't idle.

Should I get the car idling at 2k then start backing the throttle stop screw out? I would assume that if the throttle stop screw was in the wrong position that the idle wouldn't return to around 1k.

When I start it cold it revs up to around 1400 rpms and then drops to 1000-1100 after a while. I think this is normal.

Sorry if I've frustrated you. Let me know if you need any other information.

 

Its not "upsetting".... its "frustrating", because you are making it harder for people to help you. I want to help you, but I had to ask a lot of questions, and babble on about the differences between A4 and M6 idle, etc.

Use the "signature" field, and it all becomes a non-issue.

Just a suggestion, to help you get good answers. I know even suggesting this upsets some people - last guy I told to add the tranny to his signature (he asked if a "gu5 was the same as an m6"?) ripped me a complete new a..hole for going "off topic".

Its getting to the point where its more effort to try and help than its worth. The other site I hang out on is looking better every day.

 

I backed out the throttle stop screw about 5 or 6 turns tonight and got the TPS voltage down to about .56 volts, i read the sweet spot was around there. There might be a little vacuum stick problem but it was still idling well. I will see what happens when i drive it to work tomorrow.

This may be the reason that the tuner was complaining about vacuum levels at idle....