Check Engine Light at Idle

[Wschnitz]

My 1989 325i is running rich when cold and check engine light now comes on at idle. It is also running very rich with a low idle of 400-700 and it often bounces from 300-1700 when cold.

Before I check the usual ICV, TPS, AFM, and vacuum leak stuff (the usuals), anyone have some insight?

[brutus87]

I had a car do that once, if I remember correctly, the check engine light went away when I replaced the 02 sensor. Have you checked that?

[Danny]

What's a stomp test reveal?

[Wschnitz]

Stomp test isn't working believe it or not, but the o2 sensors is brand new.

[Wschnitz]

Edit: got it to work, it's throwing 1222 aka lambda #1

[nando]

well, there you go. new O2 sensor - might be worth replacing the relay too.

[Wschnitz]

Ill check the o2, but couldn't it also be the AFM or a vacuum leak.

[jlevie]

Edit: got it to work, it's throwing 1222 aka lambda #1

While that code can be caused by a bad O2 sensor, in most cases the cause will be intake leaks. Since it is probably past it's service life (100k), replace the O2 sensor and have a shop run a smoke test to locate the leaks. Note that if there is a significant leak that shows up immediately the leak(s) will have to be fixed and the test repeated until a smoke pressure of 2-4 psi can be maintained for more than five minutes.

[Wschnitz]

02 sensor is brand new, intake boot is brand new. I'm leaning towards AFM or engine tempt sensor.

[jlevie]

The AFM is a possibility, the ECT sensor probably isn't. There are plenty of places other than the intake boot to have intake leaks. It makes no sense to look for other causes until intake leaks can be conclusively ruled out.

[Wschnitz]

Update, hesitation in throttle when accelerating and cold, just little blips of throttle loss.

[dnguyen1963]

Common buddy, almost 3600 posts and you have not done a smoke test?

[Scallywagon]

Update, hesitation in throttle when accelerating and cold, just little blips of throttle loss.

Have you checked for intake leaks yet?

[Wschnitz]

Its not a fucking intake leak god damnit... Ive dealt with Intake leaks this isnt the issue, Ive replaced most of the hoses, boots, and gaskets, and tested the seals on the braking system.