On my 96 GLE automatic, I just installed new front o2 sensors. After installation,
the idle speed dropped about 200 rpm. Now when cold, the engine is around 500 rpm, which is too low. I tried adjusting the idle stop slightly, but this does not help. Can someone tell me how to adjust the warmup idle cam?

Thanks

 

The procedure to adjust the idle is in the stickies. You have to disconnect the TPS and then adjust the base idle screw on top of the IACV.

 

So you're talking about the "screw on the IACV bypass" mentioned in
the sticky? It is on top of this pump?

 

Yes - its typically a black plastic screw. It's about the size of a pea and it is right on top of the IACV...



You can actually just see the screw in that picture - look right above the wire harness black-tie-wrap to the left of the top red-arrow... the screw is partly covered by the black rubber hose.

 

Thank you.
Now are you supposed to disconnect BOTH connectors on the TPS when you do the first step in the sticky?

--> I looked at the FSM, it indicates that the TPS connector is the left one.
I disconnected it set the idle to approx 650, then shut the engine off, reconnected the TPS, started the car, and saw the O/D light flash several times, then go out.
The idle stayed about 650, but I am having problems when the car is cold, not hot like it is now, so I unscrewed the IACV bypass a few turns to raise the idle slightly. I'll see what happens when I start the car when it is cold.

 

Yes - the left one when looking from the front of the engine bay (radiator side).

If the idle is low when cold, you might have a sticking IACV/dirty TB. It would be worthwhile to clean out both as well.

Here is another older, but perhaps more useful writeup:
http://home.earthlink.net/~maxfaq/maintenance.htm#idle

 

Changing o2's will not have an effect on idle speed, especially cold idle speed.

Don't start playing with the idle adjustments, you might be covering up something else that went wrong. Did you clear any error codes after you changed o2's? If so you may have left the ECU in diagnostic mode, hance your low idle speed. That screw must be put back to the original position, the center, in order for your engine to run correctly.

Go back over your work, check connections, make sure you didn't knock something off when you were routing the o2 wires. Your o2 change should not have effected your idle speed.

 

Good point Tom. I agree that the O2 sensors definitely wouldn't trigger the low-idle.

 

I did clear the codes. I've used the Haynes as a reference and their write-up
leads you to believe the normal operating setting for the ECU screw is completely clockwise. Where is this center position documented?
I will look in the FSM now.

 

The normal operating setting is fully counter-clockwise. Fix the screw, and that should fix the idle problem as Tom indicated.

 

Yes,

I've done the Ecu reset many times before, but I've been too worn out from a week of replacing the alternator and a cv boot on a stuck axle. So this time, I didn't read the Haynes correctly, as it does say to leave the
screw fully counterclockwise as the last step in clearing the codes, then to shut off the ignition.
The FSM says: "Turn back diagnostic test mode selector to the fully counterclockwise
position whenever vehicle is in use."
( Page: EC-55)
The idle is now somewhat high. It is too late at night to mess with it now,
tomorrow I will have to reverse the procedure, screwing in the IACV
bypass screw in till it drops to I think it was around 700 rpm when I changed it today, then I will unplug the TPS and re-check the idle stop screw to make sure it stays around 650-700 rpm.

 

Yes - once you put the idle screw back to where it was, you should be back to normal...