Killed my AFM?

[Marauder42]

Definitely no suction on mine. Here's a photo I just took of the cap plugging the hole. This is underneath the intake boot, closest to the throttle body.

[bmwman91]

There are two holes in the bottom of the boot. One, as you know, feeds the hose to the ICV. The other one is supposed to have a plastic plug in it. IIRC, new intake boots don't come with that plug. Anywhere that you feel air being sucked into the intake, AFTER the AFM, is a source of unmetered air. If you have the old boot, pop the plug out of that one & put it into the new one. Hopefully that's all it is.

Technically, it isn't a "vacuum leak" since it is on the outside of the throttle body.

The other small hose you mentioned sounds like the one that provides vacuum to the fuel pressure regulator. If it is cracked, then it is a vacuum leak, AND your fuel pressure regulator will be keeping the fuel pressure too high at idle & part-throttle. That sounds like another source of the poor running symptoms! Just go to a local store & find some vacuum hose of the same diameter. It is sort of a pain in the ass to replace with the intake manifold on the car, but it isn't impossible.

Let us know what happens!

[Threehz]

Thank you, definitely was missing the plug, grabbed the one out of my old boot, put it in the new, it still idles alright, but it's really high like 1100-1300 and if I give it some gas it'll come down to an even higher idle like 1400-1500....

I unplugged the battery, going to let it reset everything then give it another go.

Hopefully tonight I can clean out the ICV and see if that does the trick.

[roguetoaster]

Sounds like good progress! Did you actually take the upper intake manifold off? If so double check the nuts and the connection for the brake booster.

[Threehz]

YEEHAW! So after unplugging the battery for a good hour, I just plugged it back in and started her up.

Runs perfectly! No CEL, nothing but a smooth idle, and she actually feels smoother than ever. All because a darn plug!

I owe it to you guys! Thank you all for the input and help!

[bmwman91]

Awesome, glad to hear that it was something cheap & simple! The ECU does adapt to things like vacuum leaks & stuff via oxygen sensor (to a limited extent). Unplugging it cleared out all of the bad stuff it learned with that plug missing.

If the fuel pressure regulator hose is cracked, replace it soon!

[Threehz]

Is that what that little hose is?

[bmwman91]

Yup. If it is busted, your fuel pressure will be too high at idle & part-throttle. The O2 sensor can compensate, but the car would run even better with that fixed.

[Threehz]

Maybe that's why I've been running rich?

Do you know the hose size for that hose?

[roguetoaster]

The FPR vac hose is listed as p/n:11 72 7 545 323 size 3.5X1.8, so I think that's 3.5mm OD, 1.8mm ID.

Glad to hear you fixed it!