89 525i m20 too lean,misses 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

[sidewinder69]

This has been asked so many times that I just post the link now:

http://www.bmwe34.net/e34main/trouble/hunting_idle.htm

Mine does it too ('92 535i), constantly when at operating temp. It'll start to chug, almost like it's missing in one of the cylinders.

I put spark plugs, high performance wires (www.bavauto.com), new intake (old hose was cracked at elbow) and filter, fuel injector cleaner, new battery and I was going to clean out the ICV but I would have to buy a new air filter so I didn't.

So try the tips on the website and see if that helps. It's prolly a 02 sensor on mine, or the old rotor and cap, I'm just too damn lazy to find out.

[ShadeTreeBill]

didn't get mine to straighen out until I coughed up the $350 for a new air mass meter..... did all the other cheaper stuff first, vacuum leaks, 02, ICV, etc. good luck.

[tintrx]

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!!!!

[daddyo8]

My Bentley book says a faulty o2 sensor can cause a too lean mixture as well as too rich depending on the problem. if you have 2 sensors you might as well replace them both as bmw recommends changing them at 60K anyway.