928 at last

I've been messing with the cables since the top end refresh, and thought things were pretty good, but today after a 35 mile highway run, once I entered city traffic the car was idling high in gear (1,000 rpm or so), and once I got it into a parking spot, and in park, the idle was "bouncing" off 1,400. I say bouncing because there was obviously a cut off switch operating that cut off the engine at that point and allowed restart below about 900. (After all the work and time over the last two years, it was a little unnerving).
I have just recently read a thread here about a similar problem and can't find it now.
Anyway, I opened the hood and manually blipped the throttle and made sure it was fully back to closed. And the idle seemed to stabilize. High, at 1,000 but stable. I should note that usually, it idles warm at about 775 in neutral, and about 675 in gear.
After some time at the office, car cooled down, and I fired it up and drove 30 miles home tonight with no issues except the somewhat high idle.
Any thoughts, comments or callous remarks about my mechanical abilities would be appreciated.

Calgary Ole

I am still new to these cars but might it be that the throttle body cable and/or the go pedal cable are too tight ? You should be able to here a click when manually moving the throttle body.... Someone help me with the name of the switch under the manifold
It tells the car to idle...

Calgary Ole

I know that if you stand on the driver side and operate the throttle with the car off, when you release you should here a slight click. I had my cables too tight and the idle switch would not kick in.
Hope this helps

Maleficio

Vacuum leak.

928 at last

Sorry, should have mentioned....The TPS is functioning as it should according to the digital readout test, going to 90 MPG on the screen in "Instant Fuel" mode after taking your foot off the pedal @ 2,000 rpm or more......so I doubt that's the problem. I originally thought it might be, (New dosen't necessarily mean good) but it seems to be working properly.

Maleficio

Vacuum leaks occur without our assistance.

Calgary Ole

I was thinking that a hot engine might not release the switch if the cables are right on the edge of too tight.
Again limited exp. here

928 at last

But suddenly after running pretty well after a major refresh job including Vac lines, elbows and testing?

I'll recheck the system this weekend though, just in case.

928 at last

Maybe a good point Ole. I'll have to recheck the tension and throttle plate positions. I'm kind of surprised it wouldn't have done it before today though. I tensioned the cables a couple of weeks ago......

Maleficio

Is it running rich?

Disconnect your lambda sensor. See what happens.

928 at last

I have absolutely no idea what a lamda sensor is or does.

Maleficio

Old school name for O2 sensor.

WallyP

As has already been said on here, the fact that the engine cuts off at 1400-1500 RPM indicates that the idle switch is closed and working, so it would not seem that sticking throttles, tight cables, etc. are the problem.

Sounds like false air (vacuum leak) or a sticking ISV are the two usual suspects. Those would seem to be the most likely source for air getting around a closed throttle plate.

Of course, if the idle switch is maladjusted, so that the throttle can be open with the switch still closed...

Maleficio

Replacing my main engine ground strap cured many problems. This strap wraps around the exhaust down tube and absorbs tons of heat at rest. Replace as soon as possible, and move forward.

John Speake

Put a vacuum gauge on the front fuel damper vaccum pipe. At idle it should read about 21in Hg. If substantially lower, it cofirms the most likely cause of the problem - a manifold leak, with false air bypassing the throttle plate/ISV.