Yet another surge at idle situation

[turbowolf]

I've read the threads on the Vortex without much help.

2001 1.8 BT surges at idle. Smoothes out when AC/Defrost is turned on. Pulling a good bit of vacuum with no AC but vaccum drops to about 20HG with AC on. (see this on boost gauge running off FPR)
I've checked EVERYWHERE for Vaccum leaks, none that I can find.
R&R throttle Body, cleaned it out well.
Raise idle speed with Vag-Com, no change.
I do have a "lazy" O2 sensor, but can't see this causing this situation.

What effect does turning on the AC/Defrost have on the vacuum system to where it might cause an idle surge? Any suggestions are appreciated, this is driving me crazy!  (and to drink!!) 

[turbowolf]

Nobody with any ideas?
Obviously with the AC compressor running there is additional load on the motor, therefore the ECU must compensate for it. But it seems that with the compressor running there is some effect on vacuum somewhere which causes the idle to hunt, surge, etc.

[Bastard]

my unitronic 630 file does the same on my car. i dont think he put enough load in it.

try adding 10 on the idle torque offset with lemmiwinks and bump the idle up 50-100 rpm

[turbowolf]

my unitronic 630 file does the same on my car. i dont think he put enough load in it.

try adding 10 on the idle torque offset with lemmiwinks and bump the idle up 50-100 rpm

OK, I'll try that & post again.

[Bastard]

how did it go?

i needed to add about +12 to my idle torque to smooth it out.

[turbowolf]

how did it go?

i needed to add about +12 to my idle torque to smooth it out.

yup. just did it, +10 idle torque & +100 to idle rpm. did smooth it out......
but I seem to have a skip & keep getting a misfire code #3 at idle. I swapped plug & coil with #2 with no change. Need to look at the injector although they are new. But at least the radical surge seems to be gone. Thanks.

[Bastard]

how many miles on the head? i needed a rebuild on mine, 3 bad hydrolic lifters and 3 bad exhaust valve guides.

[turbowolf]

Well over 100K. But since I upped the idle I'm not seeing the misfire code, but still have a skip at idle. It's amazing how strong these motors are with all of the abuse. I don't beat mine, but all that HP & tourque! 21 PSI Boost! Still keeps going like that fu--ing rabbit!

[Bastard]

soon as the weather turned colder my idle dipping is back.. more drag from the colder trans oil i think as its smooth as soon as you clutch in.

once its warmed up its better too. but it takes a long time to warm up the trans oil when you are not driving hard.

[turbowolf]

soon as the weather turned colder my idle dipping is back.. more drag from the colder trans oil i think as its smooth as soon as you clutch in.

once its warmed up its better too. but it takes a long time to warm up the trans oil when you are not driving hard.

Dis-engaging the clutch effects your idle? That's interesting. Must be a load/drag type thing. Have you ever replaced the gear oil in your gear box? Something I've been contemplating.

[Bastard]

yeah its pretty fresh from a complete rebuild. LW flywheel throws off the baseline idle torque i think.

[turbowolf]

Yea, I would suspect the lighter flywheel would have a definite effect. Do you see any better throttle response with that flywheel?

[Bastard]

i did a lot of work all at the same time. impossible to tell for sure.

car is certainly not sluggish.