Surging idle with WAR chip

[lifespeed81]

I've recently installed a WAR chip, MAF conversion, and full Borla exhaust with high-flow cat and headers on my '89 325i. Idle was great before the upgrade, but now I get a surging idle when cold (or even after a short stop when warm) that will run from 700rpm to 1000-1100rpm. I'm also running a tune sent from Brody at Miller.

I've triple checked all potential intake leaks, my ICV is spinning and good, and I've tried adjusting the idle fuel and idle speed up and down. Any other ideas?

[lifespeed81]

Anybody? I leaned out the idle fuel and it seemed to help to a point, but it still surges about 200rpm up and down.

[mavrikno13764]

Not sure if this happens on the M20, but have you checked your TPS?
When I found my idle was "surging" it was due to the ECU not knowing it was on the idle circuit. I cleaned and re positioned my TPS and Viola! clean idle.

Note: This was on a stock chip on my M3.

[lifespeed81]

Yeah, I've checked my TPS and found the correct readings at idle, part throttle, and WOT. I can also hear the unit engage just after idle, so no issues there.

In the past month I've tried quite a few tunes, some with high idles that are livable and others that barely idle at all. I've somewhat settled on accepting the surge as the fuel settings are otherwise perfect. So strange I can't tune it out however...