my BMw 540i M5's engine switches off when idle

[Wraine]

I just started having this problem yesterday, and it happened 5 times. Whenever I stop at a traffic light or park somewhere or whenever I dont push on the acceleration enough, the RPM starts goin up and down and eventually it turns the engine of, and I have to restart the car. And its fine when I accelerate.. but it screws up when Im idle.

Im not sure what the hell is going on, I was hoping someone who knew a lot better than I did to help me out. Today I drove it around at low speed and I hadnt had the problem what so ever... Im just afraid it will happen again.. and whats there I could do to fix it?

[Teh Prof]

Let's start with this: which one do you have, a 540, or an M5? Automatic or manual? What year?

[Wraine]

Ok, it's a 540i automatic transmission, 8 Cylinder Engine, 1997 Model.

[darkhorse737]

check your air filter, clean out your air flow meter, throttle body, and idle control valve with carb or brake cleaner. after cleaning those and your prob is still there, then u have a faulty sensor.

[Wraine]

Ok I'll get on all that tonight, but incase the problem is still there, is the sensor replaceable? And if so, then replacing it is the only way I assume?

[darkhorse737]

before u go suspecting sensors and switches... stay with the most probable with the least expense first.

In fact, maybe my first Q should have been... when was last tune-up and exactly what work was done on the car previous to this prob.

* i also forgot to add, if u hvnt changed fuel filter yet, you should consider doing that too along with what has been mentioned above.

** basics in diagnostics require that you rule out any mechanical problems FIRST, before you move on to the electrical side of of the probs; unless of course, the prob is indeed electrical.

[Wraine]

Ahh ok. Well the last tune up I did was a month ago. Cause I bought the car export from japan. So I had a check up done with it, tires, brakes. And the guys over at the garage said that everything else is in good shape. They did all necessary testing as far as I know.

And a week ago I changed the oil filter and changed the oil, and replaced all the used up fluids. And its been fine.

By the way, im not quite familiar with the BMW's build. as this is my first one. I've been driving a mazda before. And this engine is totaly different, is it possible for you to tell me where the locations of the above mentioned parts are except the air filters.

[Teh Prof]

Wraine, buy yourself a Bentley Service Manual for the E39 5 series, and everything about the car will be explained in detail.

[RoadsterMadness]

The obvious thing Prof failed to directly mention above is that your 1997 540i has the chassis code "E39" - something you will see referenced quote often on this and other BMW sites. The good news is this is one of the best and most beloved models ever made. I still miss my first E39 528i and intend to replace it as soon as possible in my Bimmer stable. Good luck with the new car and welcome to Teh Werkz!

[Wraine]

Thanks alot guys. Really helped, now I have somewhere to start. I'll get on it soon.

[dolam89]

i have the same problem and was wondering if u ever fix it or found a solution? i have a 1998 BMW 540i which is a E39 with a completely stock engine i already changed my speed idle control valve, crank sensor, cam sensor, air flow meter and i still have not fixed the problem! i start up my car and after a little while it turns off and repeats this ever time i start the engine. PLEASE some one help me......

[jonnny b]

im having the same problem aswell!!!!!!!!!! just changed the fuel filter yesterday and it cut out again thismorning as my missus pulled up at the lights was told by the mec who changed the filter that it is probably the idle control valve????????(got 523 e39) however it doesnt do it all the time very intermitant car runs fine otherwise someone somewere must no what this is????????

[yaofeng]

Does the E39 M5 come in auto transmission form?

[r1bby]

I've got an Audi A4 (B5) and it has a similar issue of stalling, it is the throttle body that needs replacing, I know this as I've replaced all the other parts mentioned darkhorse737 already and had a mechanic look at it. As for making it intermittent I know that decent / crap fuel makes a difference as does long / short journeys along with losing performance when pulling off.

I've not got round to replacing the throttle body as I've bought a E39 ) but I gave the Audi to the missus and now she's complaining as she does short journeys and it's more noticeable.

Oh and you can give the spark plugs / ht leads a look this can affect performance at slow speeds when pulling off in 1st gear considerably as well...

[dolam89]

alright guys my fuels pump wiring did not have a good connection.