Save the squirrels!!! (Fuel smell at idle)

[MrK]

Ever since I've stroked/cammed/compressed my m20, its been giving off this unburned fuel smell at idle that is killing all nearby wildlife when I start it up.

I figured that it was running rich at idle due to the messed up airflow that my race-cam causes at low engine speeds. I got my piggyback, and lowered the fuel input until the engine was on the verge of dying, and the fuel smell still remained. I then played with a few combinations of fuel and spark advance/retard in hopes of reducing this phenomenon somewhat, with no success.

I hooked up my car to a 2-gas exhaust analyser, and it gave me decent CO reading (1.1%) and what can only be described as a raunchy HC reading (2750!) when the norm is supposed to be less than 200.

Where do I go from here?

[Tony]

Are you using the stock or larger AFM? And is the PCV hooked up or are you venting the valve cover to atmosphere? Also which cam
are you running?

[MrK]

Stock AFM, the PCV is hooked up and not venting the valve cover to the atmosphere, and I'm running a schrick 304/304.

[Tony]

OK, mine was doing the same thing with a 284/272 cam. Idle mixture can be adjusted with the idle control screw on the afm look in the Bently Manual for its location, I'm using the big AFM and it is on the bottom right corner of the AFM.
Adjusting this on mine helped.

I also adjusted the AFM spring tension under the black top cover this gave an immediately better idle and cured my rich mixture condition at idle. The Bently manual gives you the details on how to adjust.

With that size cam your idle speed needs to be reset to 900 0r 1000rpm to help with this. Mine is set at 900rpm.

I would also install an E30 m3 air oil seperator into the pcv to prevent oil entering the intake system and causing heavy carbon build up in the combustion chamber.

[MrK]

Alright I got everything you said except this:

I would also install an E30 m3 air oil seperator into the pcv to prevent oil entering the intake system and causing heavy carbon build up in the combustion chamber.

Any chance you'd have a p/n or at least a pic of this seperator?

Thx for all your help so far...:)

[Tony]

http://www.realoem.com/bmw/showparts.do?model=1003&mospid=47312&btnr=11_0550&hg=11&fg=15

try to cut and paste this and see if it works, you will have to modify your hoses to work and if you want to you can modify your oil pan to have the oil feed back into it. mine goes into a holding can for now, I will modify the pan on the next rebuild.

Part #1 is the seperator.

All of you BMW hiperf engines have these on the them to prevent oil from getting into the intake trac, it also helps with emissions.

[MrK]

Perfect. I'll be sure to give the oil separator a shot. If nothing else, it definitely won't hurt to do it. And nothing beats ppl looking at an m20 and scratching their head, "what's THAT piece? I never seen that on an m20" LOL

[Tony]

I can tell you for a fact it won't hurt. My car was pinging and it should have not been, took the head off at 15k miles and the CC were so carboned up it was unreal.
I looked in the throttle body and could see the oil film inside and in the intake runners, very bad. If you look inside most m20 the get like this. I knew BMW had a solution for this and that they used oil/air seperators on the m cars.

Just a little research was all that was needed.

let me know how things go, send a PM if you need further.

Tony
Bimmerworld.com