QuestionHello, my name is Debbie.
I am with the US Military living in Italy. We have a 1984 BMW 320 IS with European specs. It was given to us by a friend who was moving- He owned it for 3 years and in that time never changed the oil or maintained it in any way. He said it had never given him any major problems but only used it as a second car. It has been involved in at least 2 fender benders.
It idols strange sometimes- after it has run for about 1 to 2 minutes, the idol begins to fluctuate. It idols above and below 2000 rpm, rising and falling as if I were tapping on the gas
at a steady beat. (about 1 or 2 seconds from peak to peak) When put into gear, the engine sounds normal again and won't start fluctuating until in neutral again. It will do this until the engine temp reaches about the halfway mark, and then the idol becomes normal. What I find strange, is that even after I have shut off the car for a couple of hours and the engine cools off, if I start it up again in the same day, it will not idol strange, only if it sits overnight- or more likely cools down long enough.
We have had it about 6 months, and took it with this problem. When we got it, we changed the oil, oil filter, air filter, fuel filter and checked the spark plugs. The engine sounds like it's been abused, it knocks. Almost sounds like a problem with a piston or something. Oil has leaked at one point into 3 of the spark plugs, but we haven't checked them again to see if more oil has gotten in after cleaning. A couple of hoses had splits in them, I think it was a vacuum hose- which I repaired with electrical tape for now. This didn't seem to change anything. I don't know if it's normal or not, (been a while since I've driven a stick) but it sounds like the engine runs at a higher rpm in neutral than in first gear, and about the same in neutral and second.
Yesterday it wouldn't start. The battery seems fine, and the starter motor works. However, the engine doesn't even try to engage. It was almost out of gas, so I put in 2 gallons to be sure it wasn't because I'd run out. Still nothing. I drive it twice a week, and last time I drove it, it behaved the same as always. The weather has been rainy and humid, (don't know if this can effect it) but I've not had previous problems starting it in rain, humid or cold weather.
Because we will be giving it to someone else when we leave in 3 years, I'm having trouble convincing my husband to put much money into fixing it beyond safety repairs. I can work on it myself, as long as I am able to locate and identify the problem parts. (I'd prefer this, it's good practice) We were told by a co worker that the idol is due to a electronic part having to do with the fuel injection, but this guy is no mechanic. (Although it sounds right to me)
I have access to local junk yards and am willing to scour for parts. I also have access to the Auto Hobby Shop on base, where I can use their tools, lifts, and rent space to work for dirt cheap. They also have a mechanic on hand to supervise and answer questions, so I feel good about trying most repairs myself.
I very much appreciate any information you can give me to help me get started, and thank you for volunteering your time!
Debbie Hallahan
AnswerHey,
Unfortunately i have never worked on this model car since it's only sold in Europe, but i should be able to give you a general idea how the car stabilizes the idle.
The fact that the car does not start up in adverse weather tells me their is a good chance the problem is electrical.
Check all the grounds (one from the engine to the body in the engine bay, the main ground for the battery in the trunk (unless your battery is under the hood). This is what i think is happening:
You start up the car and the computer goes to a preset mixture and timing, as the car warms up (approximately 2 minutes) it goes into whats called closed loop where it gets information from all the sensors and determines the best and most efficient air fuel mixture and timing. What i find puzzling is the fact that it goes normal after a while, this tells me perhaps the idle control computer is getting a bad ground or is faulty (it's mainly located on the firewall in front of the driver or in the cowling for the windshield wipers)
I know that on my USA model 320i the idle would fluctuate when the oil is low, vacuum leaks and when the valves needed to be adjusted.
You can check for vacuum leaks with a propane tank by letting the car idle and blowing the propane over where you suspect a vacuum leak. it would be helpful if you can find a exaust gas analyzer to see what the mixture is doing. their are a lot of possibilities but my main suspect would be the idle stabilizer.
best of luck!
Thanks for the effort you put forth to support our country!
