89 525irunning too lean,skips and stumbles in idle & drive

[tintrx]

Hey guys, let's see who can solve this mystery. My 89 525i is running way too lean. I stomp tested to get an afm code.No change after three different meters were installed. I checked for vacuum leaks and found one at the intake. After fixing that the car ran better but the sinario of stumbling and too lean fuel mix still pursists. I was told that I might have and ecu malfunction, so I changed brains to see if that would work. Nope, still the same; however, I now can get a reading change on the exhaust analyzer now, but it's still running the same. Some days it runs halfway decent, but lately its been running really choppy and cut off while driving. I'm not sure if it's a fuel or ignition problem. There are not enough signs for me to tell either way which one it is. Anyone who has any suggestions, I would certainly appreciate any help I can get. Thanks in advance

I think I solved one problem to create something else. When I changed my coolant temp sensor the problem immediately went from occassionally stumbling to won't run at all unless I give it gas. I pulled plugs to find fluid on cylinders 1,3,5 and carbon on 2,4,6. I had my valves adjusted and did a pressure check on the coolant system and I found no leaks and it held pressure all night and into the next day. I haven't done a leak down check yet but I don't think that I'm having a cracked head problem. I'm sure I've overlooked something, but I'm not sure what it could be. There's a guy in my area (Greensboro, NC)who I'm told is an expert on e34's but it's probably going to take 2 weeks before he can even look at my car. If someone has any advice in this matter it would surely be appreciated. My wife and I are down to 1 car now and it's getting really aggrivating trying to juggle two schedules with 1 vehicle. Pleassse Heellppp!!!!

[bsell]

Hey guys, let's see who can solve this mystery. My 89 525i is running way too lean. I stomp tested to get an afm code.No change after three different meters were installed. I checked for vacuum leaks and found one at the intake. After fixing that the car ran better but the sinario of stumbling and too lean fuel mix still pursists. I was told that I might have and ecu malfunction, so I changed brains to see if that would work. Nope, still the same; however, I now can get a reading change on the exhaust analyzer now, but it's still running the same. Some days it runs halfway decent, but lately its been running really choppy and cut off while driving. I'm not sure if it's a fuel or ignition problem. There are not enough signs for me to tell either way which one it is. Anyone who has any suggestions, I would certainly appreciate any help I can get. Thanks in advance

Have you verified fuel pressure to be a non-problem? Low fuel pressure can cause a lean condition at idle.

You have, of course, done the basic tune-up checks, right?;)

Either you got three bad AFMs in a row or the problem lies elsewhere.

Didn't somebody post on here that his coolant temp sensor gave him driveability problems? For something under $20 (US) he put in a new one and his problems where solved after many hours/dollars spent chasing fuel injection system gremlins to no avail.

Brian

[tintrx]

Have you verified fuel pressure to be a non-problem? Low fuel pressure can cause a lean condition at idle.

You have, of course, done the basic tune-up checks, right?;)

Either you got three bad AFMs in a row or the problem lies elsewhere.

Didn't somebody post on here that his coolant temp sensor gave him driveability problems? For something under $20 (US) he put in a new one and his problems where solved after many hours/dollars spent chasing fuel injection system gremlins to no avail.

Brian

Initially I thought that I was having a tune-up issue when this thing first started, so I changed plugs, changed wires, fuel filter, etc... The guy that I finally took my car to found the vac leak and checked for other problem areas like the fuel pressure, O2 sensor, afm adjustment, and a few other things that I can't remember right now, but after a few days of poking around he couldn't find the main problem at hand. I guess that I have to take the blame for thinking that a porche guy could handle my beemer problem. Anyway, thanks for the tip about the coolant temp sensor, I'll check into it right away. I'll let you know how it turns out.
Thanks for your input.
Jeff

[bsell]

Initially I thought that I was having a tune-up issue when this thing first started, so I changed plugs, changed wires, fuel filter, etc... The guy that I finally took my car to found the vac leak and checked for other problem areas like the fuel pressure, O2 sensor, afm adjustment, and a few other things that I can't remember right now, but after a few days of poking around he couldn't find the main problem at hand. I guess that I have to take the blame for thinking that a porche guy could handle my beemer problem. Anyway, thanks for the tip about the coolant temp sensor, I'll check into it right away. I'll let you know how it turns out.
Thanks for your input.
Jeff

I'll say your welcome if my guesstimate works out.:D

Porsche used to use a very similar style fuel injection system back in the day (late '80s) so depending how long he's been working on them, you didn't do too wrong going with him.

Brian

[tintrx]

Hey brian,
I changed that coolant temp sensor. Slight improvement was noticed. My car no longer stumbles in idle, but still the same in drive when I put a load on the motor. Also, the stumble is a little less consistant than before. I going to try to make and adjusment on my afm to see if I can get rid of stumble. Any more I ideas that you may have would be appreciated.
thanks,
jeff

[tintrx]

I think I am start to narrow things down. It seems as though the stumbling problem triggered or made worse by a change in climate. Cooler temps helps the car to run better w/o stumbling. Temps above about 55 degrees cause the stumbling. The stumbling doesn't happen at idle, only when motor is under a load. Is there a sensor or something that could malfunction and create this situation?

[tim eh?]

maybe you checked the distributor cap and rotor already but if you haven't i think it would be a good thing to look at.

[tintrx]

Thanks, I'll check it out and get back to you. I did however change the coolant temp sensor, Nojoy.