1991 325i m20 help, madison

[cpandrewschmidt]

Ugh, frustrated.  Changed out the wires (thanks JC) and put in some NKG plugs just in case.  Still getting the same problem.  

Out of ideas

[B C]

Afm

[jc43089]

Snap, what happens with the afm unplugged?  Does it use default safe tables?  That could be a way to test by trying to run it with the afm unplugged.

[Jdesign]

I am in Madison and am more than willing to take a look at your car. I am sure we could get to the bottom of this in a few hours. You should compose a list of everything you swapped out or replaced in attempt to diagnose the problem. Shoot me a text and when you have time, swing by my shop and I can help you get this sorted, like you said, I am sure its something simple.

414.eight52.five943

[cpandrewschmidt]

Thanks guys, you all rock for offering to help like this.  

I've tried unplugging the AFM and the car just stalled and died so I'm not sure it can run without that plugged in, i don't think so.  

I'm going to try cleaning the AFM tonight and moving the track slightly on the electronic sensor like this guy does.  I opened it up and I definitely have two distinguishable spots of wear along the track.   

http://www.r3vlimited.com/board/showthread.php?t=247831

I don't totally understand how the AFM works but this might be it.  The thing I don't understand is does that arm constantly move along the senor pad, or does it only adjust while pressing the throttle?  If it's the later I don't think that'd be my issue because the car sputters even when in idle.  However, if that arm is constantly moving based the other sensor in the air box it'd make sense for the car to sputter when it hits the dead spots along the track.  

Either way, I'll report back tonight!

[jc43089]

When there is more air moving through the afm it opens then flap which is linked to the wiper.  The cross section inside of the afm increases as it opens so it will open in a somewhat linear way through the range of airflow.  The air is based on how far the throttle is open.

[cpandrewschmidt]

Hi all, quick update.  Snap looked and tested my AFM.  did show signs of dead spots.  So, since i didn't have a new one I just put it back in and also re-swapped out the OEM wires and plugs back to the newer performance ones / bosch plugs.  So, all the same stuff. 

I was going to meet John Thursday in Cottage Grove to look things over.  I wanted to make sure I could make it that whole way from the westside so I took the car out Wednesday night to my wife's Happy hour just to make sure it woudn't die.  It sputtered for about 2 mins then settled down.  I hit a detour on my way which made me have to go 70mph on 151.  Took me about 30 mins to get around town.  Car ran great, no issues.  Let it cool down while we ate for several hours.  Fired it back up on the way home.  No sputtering at all.  

So, Thursday I decide to try taking it to work along the Beltline.  Fired it up, no issues.  Drove around all day Thursday and took to work again today.  I'll probably jynx myself for typing this, knock on wood, but no issues.  Nothing different that i did.  So, no idea but I'll take it for now!  I'm not touching anything  Actually have a few drips i have to stop, but at least I feel I hopefully wont break down.  

Just wanted to say thanks again for everyone's help.  I definitely learned a lot about this engine through all this.  

Andrew

[Earl]

You learned that m20's can't be trusted and it needs an m50 swap right?

[cpandrewschmidt]

Earl said:

You learned that m20's can't be trusted and it needs an m50 swap right? 

Ha, yes.  Maybe when this one dies.

[straight6pwr]

Glad you got it solved.