Idle on 3.2

[Nick Triesch]

The idle on the 3.2 is maintained by Motronic. What then are the idle adjustments for in shop Manuel? Thanks. Nick

[911obgyn]

Base idle needs to be set with CO meter or wide band oxy sensor.
Manual explains how. I fixed a hunting idle using that procedure.

[Nick Triesch]

Thanks

[FA-18C]

Nick, as obgyn stated, when jumping the O2 sensor input, you set your base idle. Over time with various wear and leaks, you can get lean or rich. Too rich can give you a "lumpy" or hunting idle. Other contributors are potential bleeding of fuel into intakes from your damper and fuel pressure regulator, and a clogged up or faulty idle control valve.

[ischmitz]

There are actually two adjustments for a 3.2.

One is the idle mixture where a certain amount of unmetered air is passed into the engine through the bypass screw on the AFM and the rest of the air goes through the AFM flapper. This sets the mixture at idle is checked with a CO meter pre-cat.

The other adjustment is the stop position of the throttle plate. This adjusts how much air gets through the throttle plate during idle. The rest comes through the ICV. For this adjustment the ICV gets centered (paper clip or diagnostic plug into 3-pin female connector in engine bay). This adjustment pretty much sets the base position of the ICV to where it then can act to increase or decrease air flow to maintain idle.

[mysocal911]

Originally Posted by FA-18C

Nick, as obgyn stated, when jumping the O2 sensor input, you set your base idle.

You mean disconnecting it, right? "Jumping" will cause a very rich mixture.

Originally Posted by FA-18C

Over time with various wear and leaks, you can get lean or rich. Too rich can give you a "lumpy" or hunting idle. Other contributors are potential bleeding of fuel into intakes from your damper and fuel pressure regulator, and a clogged up or faulty idle control valve.

Small changes of the mixture are typically compensated for when in a closed-loop mode, i.e. the O2 sensor being connected to DME ECM.

[FA-18C]

Let me restate, follow Bentleys for adjusting idle.

[Nick Triesch]

When I start my 3.2 it warms up perfectly the way it’s supposed to then settles to a nice 8 on the tachometer. But then when I drive it sometimes I come to a light and the idle goes down to about 7 or 7.5. Then pops right back to 8 thousand . Not a big deal. Car runs great and not hunting all over the place. I tightened all the hoses near motronic and ICV is good. I was sick for several months in 21 did not drive for months. Cancer broke my shifter arm . I’ll drive it more now . Thanks.

[mysocal911]

Originally Posted by Nick Triesch

When I start my 3.2 it warms up perfectly the way it’s supposed to then settles to a nice 8 on the tachometer. But then when I drive it sometimes I come to a light and the idle goes down to about 7 or 7.5. Then pops right back to 8 thousand . Not a big deal. Car runs great and not hunting all over the place. I tightened all the hoses near motronic and ICV is good. I was sick for several months in 21 did not drive for months. Cancer broke my shifter arm . I’ll drive it more now . Thanks.

Then it under-shoots! This can be corrected by turning the throttle bypass screw a quarter turn counterclockwise, i.e. a little more idle air.

[FA-18C]

Dave, so running rich then, correct? I chased this for a couple weeks and then discovered my fuel damper was leaking fuel into the vacuum hose into the intakes. Changed that and the start and warmup and idle is rock solid. That was the basis of the point above - at least what I was trying to make, it is not always an easy adjustment to the throttle bypass, until you sort out other potential issues you can be adjusting that back and forth alot.

Nick, if you have been running rich for awhile, this could be as simple as cleaning up some partially fouled plugs.

[mysocal911]

Originally Posted by FA-18C

Dave, so running rich then, correct? I chased this for a couple weeks and then discovered my fuel damper was leaking fuel into the vacuum hose into the intakes. Changed that and the start and warmup and idle is rock solid. That was the basis of the point above - at least what I was trying to make, it is not always an easy adjustment to the throttle bypass, until you sort out other potential issues you can be adjusting that back and forth alot.

Nick, if you have been running rich for awhile, this could be as simple as cleaning up some partially fouled plugs.

No, just that the idle valve can't respond that quickly, and the idle RPM under-shoots the desired RPM.
The valve, though, can eventually compensate for the additional air by closing the valve just a little when the RPM stabilizes.