got a 90 vert, since i got it the idle seems high. it does the 3000 start idle and then drops like it should, but once it warms up it should drop again. it does not. it idles like it is cold all of the time, on a few occasions it has dropped to around 800rpm, but is definitely not the norm. now to add to this, and the reason i decidedc to post up about it, it is fluctuating at idle once it warms up. not a fast drop rebound, but a slow one. it spans from about 1300 to 1600 rpm.

i figure this to be a vacuum problem, but have not looked into it really. the only thing i have done to it lately is to take off the intake piping and clean the throttlebody. but this was a few weeks ago, and it was not very dirty to begin with. i am certain that i got all the hoses back the way i found them.

any help would be greatly appreciated.

 

Try that.

Also read this.

Good luck, I've always just let my cars idle at 1100-1300 and taken all of the excess systems out.

 

interesting read, but do n/a motors have the same valving systems on them??

 

Pretty sure all those systems are common to both models. The FSM should confirm one way or the other, as well as any location differences between the two.

 

My experience leans toward vacuum leak. I had idle pblms with my 87TII; couldn't idle below 2500. i replaced all the small rubber hoses on top of the engine and immediately got it down to 1500.
Further exploration found a split in the plenum hose between the AFM and the turbo intake. I fixed it with high-temp RTV and a better clamp.
Now i have rock solid idle at 750.

- k -

 

Aside from trying out what everyone has mentioned above.. make sure you tightened down your UIM correctly. i've bolted mines down incorrectly and the car ran like ****. so give that a shot

 

thank you guys for the input... i did not remove the intake, just all of the piping to the throttle body. si i will recheck that and replace vacuum lines. it drives fine, and everything is fine with load, it is just the idle prob...

where can i find info on adjusting the idle, if i can get it to smooth back out and it is still high?

 

okay i just did an inspection on the vacuum lines, they seem to have been replaced. no signs of cracking or rotting... not sure what is going on with it. where are these idle/air control devices located, what do they look like??

 

i think this is right, but its possible i have the names messed up
oh, and this is for a S4 NA, i dunno if there different for S5, but this should give you an idea of what they look like.


AIR BYPASS SOLENOID VALVE




BYPASS AIR CONTROL VALVE