AAV Question

[76was124]

I also took the temporary measure of increasing the throttle plate set point to artificially raise the idle, then shut down the idle screw completely,

Yeah seems like idle just over a 1000RPM works for me. I need to get a tach, so I know what it really is verses the tach in the instrument panel.

Weird because I know I had it working perfect until I messed with the throttle stop and idle screw and subsequently the TPS. So I am going go try more tweaking. The idle screw o-ring is on my list too if you find one.

BTW, you probably know you don't need to pull the head to do the injector on-rings, but just in case, I thought I would mention it.

[RRoller123]

If you find the proper size for the o-ring, let us all know, please. Understood about pulling the intake, I want to put a new gasket on just to be sure. The injector seals can be done w/o pulling it, yes. S

Sounds like you have the exact same problem as I do. I am going to start digging into the AFM again and see if there is anything obvious going on there. I long ago moved the arms to fresh TFM and that solved a lot of stumbling and flat spot issues, but made no difference with this particular problem.

So my current candidates to investigate are:

low regulated fuel pressure?
AFM spring too loose, allowing flap to oscillate?
AFM bypass wildly mis-set?
leaking injector seal/s?
leaking idle o-ring?
leaking intake gasket?

[76was124]

1. low regulated fuel pressure?
2. AFM spring too loose, allowing flap to oscillate?
3. AFM bypass wildly mis-set?
4. leaking injector seal/s?
5. leaking idle o-ring?
6. leaking intake gasket?

Okay for comparison purposes...Here's where I am at.
1. Regulator tested okay, but I am creating a vacuum in my tank...I leave the gas cap loose, or the cap off the canister (which doesn't have the proper cap(with a metered vent hole), just a plug.
2. Unkown
3. AAV?mine fully closes, AFM,, mine is used, flap fine, but plug is missing over mix screw.
4. I have brand new injectors and seals
5. Unknown
6. New head gasket, full engine rebuild, including valve adjustment.
7. New vacuum advance diaphragm on order, hose plugged for now.
8. Need to test brake booster for vacuum leak

[RRoller123]

The cap over the AFM adjustment screw opening is just to keep owners like us from fiddling with it.

[RRoller123]

There is a wealth of info on YouTube, just need to prioritize what to investigate first.

This sort of thing is what I am talking about checking for under the cap:

http://www.youtube.com/watch?v=n3TTVbos7uY

This is a good one too:

http://www.youtube.com/watch?v=yQukm7lNux4

[76was124]

Hi Pete,

I just found something on my car that could be a contributing factor to the idle drop issue during a fast stop. I have a single frayed strand on my accelerator cable. It was at the edge (where it comes out of the cable jacket) when I get near the idle stop position. I am hoping that may have occasionally slowed the throttle plate return and TPS switch point. I need to order a new cable.

You may want to inspect yours closely if you haven't, but that would be a heck of a coincidence if you had the same problem.

[RRoller123]

Thanks for the tip, I will check that out!

[RRoller123]

Follow up: Not a fuel pressure problem. 35 at the pump, 27 regulated. Tested with a gauge t-ed off the CSI.

Did find a very interesting issue to share with the forum however: When setting the idle per factory manual method, I discovered that the Throttle Position Switch, where it was set at the time, was just slightly restricting the full closing of the throttle plate as I backed off the screw.

So my new procedure is to completely loosen the TPS, set the screw, then the idle bypass, as per shop manual, THEN set the TPS to click at closed throttle.

This eliminated almost entirely the issue I had where the RPMs would drop very low when coming to a stop, then slowly come back up over a few seconds, building to normal. Sometimes it is the smallest, most subtle and simplest things that evade discovery and cause long bouts of tremendous irritation. But they always lose in the end.

[bradartigue]

Hi Pete,

I just found something on my car that could be a contributing factor to the idle drop issue during a fast stop. I have a single frayed strand on my accelerator cable. It was at the edge (where it comes out of the cable jacket) when I get near the idle stop position. I am hoping that may have occasionally slowed the throttle plate return and TPS switch point. I need to order a new cable.

You may want to inspect yours closely if you haven't, but that would be a heck of a coincidence if you had the same problem.

A frayed cable is also a stretched cable. Stretched cables limit the throttle movement.

[76was124]

When setting the idle per factory manual method, I discovered that the Throttle Position Switch, where it was set at the time, was just slightly restricting the full closing of the throttle plate as I backed off the screw.

I thought I would reset my idle and found I had exactly the same issue as you. TPS switch was preventing the throttle plate from fully closing. It made a big difference and explains why previously a fully closed down idle screw didn't lower the idle to near stall. It does now! Nice find Pete!

[RRoller123]

Bingo, that's why we are here, to share our discoveries on this stuff. We will all be experts eventually. I am almost scary myself at the Cruise Nights when I start explaining to visitors how all the FI plumbing under the hood works. Thanks Brad and Mirafiori!