High Idle

[robairx]

My 98 Disco 1 idles at 1700 rpm in P/N drops to 1000 in R/D. I have searched the forums and tried Cleaned the idle air control valve. That did not help removed the battery cable overnight Still high idle Got a new idel air control valve from advance auto parts ($37)
and still idle too high have pulled idle air control vale and watched it doesnt seem to be moving Does anyone know how I can Check to see if it is getting a signal I have a scanner it reports no codes Howeer about once a month I will get a misfire code. I have cleaned the MAF with MAF cleaner no change Thanks for all your Help

 

[Disco Mike]

Did you decarbon the IAC and where it mounts to the manifold, how about the t/body, have you cleaned it?

 

[robairx]

I did clean the throttle body and searched for vacuum leaks Not sure what you mean by decarbon But I have replaced tha Idle air control valve Idle has changed but has only gone higher

 

[greg409]

the iac extends within 20sec after key off

on key on it retracts gives you the vrroomm on start.

A new one needs to get friendly with the ECU to work properly.

Try searching the forums for - iac reset- or something like that.
It involves turning on/off key and unplugging iac and holding 2k rpm for 30sec. I think it may work.

I bypassed mine b/4 finding this out & probably will try that when I get to it.

luck,greg

 

[beemer]

the iac extends within 20sec after key off

on key on it retracts gives you the vrroomm on start.

A new one needs to get friendly with the ECU to work properly.

Try searching the forums for - iac reset- or something like that.
It involves turning on/off key and unplugging iac and holding 2k rpm for 30sec. I think it may work.

I bypassed mine b/4 finding this out & probably will try that when I get to it.

luck,greg

I know the 95 and older 3.9 IAC is the same off a GM V6 hell it's a old GM motor. This thru Pick N pulls collection for free or $47 at a parts store. Rover price bend over with lube.
Post 95 I do not know if the IAC fits other vehicles, if so look there at Pick N Pulls or their stealers. Even Rolls Royce must be cheaper than Rover stealers prices. Chech with www.autohausaz.com. They have parts for every make and cheaper with OEM parts.
I would spray with Berryman B12 carb cleaner then apply some liquid lock lube that has graphite which stays behind as a dry lube. This I have used for years with so called junk IAC units that work after cleaning. Also clean out the port inside the plenum as they get nasty on a rat motor with a lot blowby.
No "vrroomm" here, I added an adjustable restrictor inside the idle bypass hose (not seen by smog test inspections to limit my idle by 50 rpms above a hot idle to allow for AC loading plus a slow 550 cold start idle rpm only.
This with a pre-oiler for 26 psi before starting every morning. The factory cold start idle rpm's are way too high to quickly warm up the cats which is 90% or higher of your daily cold engine wear.

 

[Spencer]

I needed to get my adaptive memory reset.