toddk911

Symptom:

A few times over the last couple of months when letting the car go into neutral and just coasting after higher revs/boost, the idle will drop pretty low sometimes will stall.

This is more promenent after a boost/high rev accell. Then the next day or say it is fine.

I can aid by tapping the throttle on the way down so it stays in the 900+ range and then will hold idle.

Could this be bad/going bad ISV, other vac issue or just a distruption of air into/through the MAF?

TIA

minho78

Todd911k, I fixed the same problem by adjusting the TPS, and the Idle adjusting screw. I adjusted it to idle at 950rpm. Hope this helps.

choinga

I ran into this as well and it seemed to intensify after I installed a MAF. I called it an 'idle bomb'.

I dinked around with some stuff thinking it was a vacuum leak...I did find that one of the small silicone hoses that was under the intake (the one that goes to the bottom of the throttle body) had a small rip and I replaced that but doubt seriously that was the primary issue. While the intake was off I put in a brand new ICV and TPS and my problem went away. I did all of those at the same time so not sure if it was a single one of those that fixed it or a lucky combo of all three.

toddk911

Excellent.

I did adjust the idle before and it helped but not the TPS.

How did you adjust the TPS?

toddk911

Ok, Choinga, thanks.

So that is two for TPS, so i will def check that.

JohnKoaWood

From Clarks Garage, Throttle Position Sensor...

http://www.clarks-garage.com/shop-manual/fuel-06.htm

"Replacement and Adjustment

Normally Aspirated cars:

Remove the throttle body from the car.
Remove the two Phillips head screws that attach the TPS to the throttle body.
Install the new TPS and insert the mounting screws. Do not tighten the screws until the adjustment is complete.
Hold the throttle in the closed position and turn the TPS until the internal stop is felt and tighten the mounting screws.
Check the adjustment by turning the throttle toward the open position. An audible click should be hear as soon as the throttle starts to open. Slowly close the throttle until it is fully closed. Do not force the throttle closed. Allow it to close under spring pressure only. Just prior to going fully closed, an audible click should again be heard. If the click is not heard, readjust the switch.
Install the throttle body.
Turbocharged cars:

NOTE
On turbocharged cars, the throttle body does not have to be removed from the car. However, the bottom mounting screw for the TPS is extremely difficult to remove and install. So, I always replace the Phillips head screws the 4 mm Allen head bolts. They are much easier to remove and install than the Phillips screws - especially if you have a long ball head Allen tool.


Remove the two Phillips head screws that attach the TPS to the throttle body.
Install the new TPS and insert the mounting screws. Do not tighten the screws until the adjustment is complete.
Hold the throttle in the closed position and turn the TPS until the internal stop is felt and tighten the mounting screws.
Check the adjustment by turning the throttle toward the open position. An audible click should be hear as soon as the throttle starts to open. Slowly close the throttle until it is fully closed. Do not force the throttle closed. Allow it to close under spring pressure only. Just prior to going fully closed, an audible click should again be heard. If the click is not heard, readjust the switch.

Clark's Garage © 1998"

minho78

The first time I did it according to clarks garage, and It didn't work that well. The I adjusted it right by the click sound. No more problems, and the idle doesn't go below ~900 rpm.

choinga

You can't reliably adjust by just the clicking sound. Honestly, I think mine was probably working OK but I was just tired of dealing with it and wanted to elimate all possibilities and while I was in there (I had the TB off and rebuilt it using the Arnworx kit) I just figured I'd go ahead and replace it. The Arnworx kit is nice because you can then replace your phillips screws on the TPS with hex bolts which makes that back one a helluva lot easier to get to if you have to make any adjustments after you bolt the TB back on.

I ran through the tests on Clark's and mine checked out OK, so it was probably fine and it was pretty clean inside. I'm guessing my issue probably had more to do with the ICV, that vacuum leak and some ground gremlins that haunted me for awhile after installing the MAF than anything else. Oh, I also replaced the O2 sensor while I was doing all this as well.

Now, of course after you do all of that you'll have to reset idle. One thing I didn't know until recently that someone told me (and not sure how true this is or if it has any effect)...you should jumper the DME before you start the car and let it get warm and then set idle with the screw. I had been driving it around or whatever...pull back into the garage, jumper it and then set it. My idle seems OK though...so if it ain't broke...don't fix it...it goes a little high when it's cold but never over 1k RPM.