Air Flow Meter

[Paaancho]

Anybody have one. Mine went bad. I installed a new muffler yesterday so i was excited to hear what it sounded like so i turned on the car without the air box and intake hooked up and it sounded good. A bit of a rough idle i figured because not everything was hooked up.

i hooked up the intake and all that nonsense the car would start and die in about 4 seconds. So i left the airbox but started disconnecting the wires attached to the sensors on the box one at a time and when i disconnected the mass airflow meter it fixed the problem...not a perfect idle but it idled.

Is there a remedy to this...other possible scenario or does it seem like a good diagnosis?

Anybody have a spare they would be willing to part with for a good price?

let me know thanks

[thejlevie]

Before you replace the AFM, check for intake leaks. Especially the intake boot. An intake leak can cause the engine to run ruogh or die with the AFM connected and run okay with it disconnected.

[EthirtyIS]

i have the same problem on my 91 318i... it runs but once i plug in the air afm the engine dies.. if i stay above 3k the engine runs fine. but the strange thing is that even if the afm is not part of the system, not hooked up to anything, and i plug it in it dies...
my plan of atack was to take it apart and clean it out.. then try again.. any other ideas?

[Paaancho]

I found some leaking fuel hoses so i plan on replacing all of them this weekend...do you think this may also help rectify the situation

[kharv]

if fuel delivery is a problem then it is possible that it would die.

[ericgoum]

I recently had a problem like this after finally fixing the idle control valve circuit. Before it was fixed, un-metered air would get into the engine through the ICV making the engine run poorly(idle that varied between 800rpm to 2000rpm). When I fixed the problem, which happened to be a blown fuse #9 (among other things), it would start up then immediately shut down. I ran through my Bentley manual fuel system test procedure and finally isolated it to the Fuel Pump Relay. It is located in the little auxiliary relay box kinda between the AFM and the side of the car.

You can test to see if the relay is faulty by setting up a fused switch to test for fuel pump operation. If the pump works with the switch setup, then the relay is bad. I can't remember exactly which pins to connect the switch to, and which to just tie together. If you have a Bentley manual it can tell you what you need to know. If you don't have a Bentley manual I could send you some better instructions if you PM me.

I hope this helps and wasn't too long winded, I just thought it sounded similar to my problem.

Eric

[Paaancho]

sounds good. I just got the bentley manual and started skimming through some of the troubleshooting sections...it looks like i have a nice checklist to go through.

[Paaancho]

I finally got around to checking out whatever problem i've been having with this thing...still nothing.

I've checked my injectors: good,

Replaced all fuel lines because they were pretty cracked up

.

Put in new spark plugs and cables (oem recommended)

I knew my O2 sensor was going from a while back so I replaced it with a new one

Still having the same problem.

AFM plugged in=car turns revs to about 2000rpms and dies pretty much instantly

AFM unplugged=Car idles roughly but consistently at about 800rpms. When it is like this the exhaust fumes smell rich.

Fuel pump is good...i just changed it about a month or two ago.

At this point I'm stuck dont know what to do. Removed my airbox one day...came back a week later and now this problem.
Would a bad valve lash cause this?
My cars valves are pretty off.

If anyone has anymore suggestions that would be awesome as I would love to start driving my car again. and i only have weekends to work on it so today and tomorrow are the days until next week.

Thanks

P.S. long post sorry

[thejlevie]

The first thing to do would be to check the fuel pressure in the rail. If within spec, the odds are that you have an intake leak.

[ericgoum]

Did you get around to checking the operation of the fuel relay? It sounds like when everything is hooked up you get full fuel pressure when key is in the start position, which I think overrides the fuel relay, but when you take it off the start position it then checks a crank sensor which sends the (car is running) signal to the relay. If the relay or sensor are bad then your engine will die. I think weird things happen within the computer when the whole system is not running properly. As I said in my earlier post, the fuel system acted weird and would run poorly when the ICV wasn't working. When I replaced that I suddenly had the same issue as you and only when the fuel relay was replaced did it work.

Sorry for yet another long post.

Eric

[Paaancho]

Originally Posted by thejlevie

The first thing to do would be to check the fuel pressure in the rail. If within spec, the odds are that you have an intake leak.

Does this have to actually be pressure or can the rate be checked...30oz in 30seconds. I only ask this because i dont have a pressure guage.

Originally Posted by ericgoum

Did you get around to checking the operation of the fuel relay? It sounds like when everything is hooked up you get full fuel pressure when key is in the start position, which I think overrides the fuel relay, but when you take it off the start position it then checks a crank sensor which sends the (car is running) signal to the relay. If the relay or sensor are bad then your engine will die. I think weird things happen within the computer when the whole system is not running properly. As I said in my earlier post, the fuel system acted weird and would run poorly when the ICV wasn't working. When I replaced that I suddenly had the same issue as you and only when the fuel relay was replaced did it work.

Sorry for yet another long post.

Eric

its cool usually the longer the post becuase more reason leads to better understanding i guess...dont have any jumpers but i'm probably going to hit the pick a part tomorrow so if i see any relays ill probably snag a few...and some vacuum advance ones while i'm at it since theyre right next to em haha

[thejlevie]

Does this have to actually be pressure or can the rate be checked...30oz in 30seconds. I only ask this because i dont have a pressure guage.

Ideally you test both, but between the pressure and flow test the pressure test is more important in this particular case.

[Paaancho]

K. I got close to the 30 in 30 ratio but still can't measure pressure. I also went ahead and changed out some vacuum lines (some of the old ones were so bad that if i stretched them a little they would break). I'm guessing there are still some leaks somewhere in the system so i have to continue the search. The ones i did change did make a noticeable difference though (distributer-tps, tps-throttle body, fpr-TB, and one more i forget which).

It is still idling pretty rough but will stay on for about 5 seconds and bog out unless i feather the gas to keep her alive. Once it warms up though it will idle at a pretty consistent 1100rpms with surges to about 12-1300 or bogs to about 900. my dad suggested that it may be a bad temp sensor. Does that sound plausible?

This Saturday I'm planning on doing the valve adjustment just to get that out of the way and know thats good (and it neeeds it) unless my pops decides to do something to the gazellebeige 4dr he got this week.

PS i wish i could rename this thread
PSS thanks to the guys that have helped me in my quest to find a steady idle and to those that will help me later haha