Engine completely die when come to a stop
 

Lately my 89 300e completely died when it come to a stop sign or red light. This happened to me on Wednesday and happen again today when my wife drives it. In both cases, we just restart the engine without any problem. I just spend $700 last weekend to have the transmission resealed, are these somehow related? Or what could be wrong? It never had this problem before. The car is almost reaching 130,000 miles. Any idea?

You may need to clean the trottle body bore. With time deposits build up in the bore right at the butterfly valve choking air flow during idle.

It happens again when I come in to work on the freeway this morning. At stop and go traffic, at sudden all lights on the dash come on without any warning, the engine is not even shaking at all before it die. If I did not pay attention to the dash, I do not even notice that engine is not running. Is this something to do with the electrical system, could it be possible that when this guy remove the transmission doing his work, somehow something got loose/damaged by accident? It is a terrible feeling that you don't know when your car is going to stop running. Help!

Okay, with all the dash lights coming on it's not the throttle body bore. It sounds like all power goes out momentarily before the engine dies. The dash lights come on for the same reason they come on when you turn the key in the ignition. Check electrical connections under the hood. It may be as simple as dirty battery post connections that need cleaning. Check the grounding strap for the engine. Sometimes mechanics forget to reattach the strap. Check all other grounding wires.

Thanks for the input. By talking to my mechanic, he was saying this might be something to do with the idle control system, any thoughts? If that is the case, what consists of the idle control system and what could go wrong?

I was experiencing the exact same problems.
I took out the idle control valve. Cleaned it thoroughly with brake cleaner. Spray the inside (thru holes), let it sit for a while, shake it and repeat the procedure until the liquid comes out clean. Then I sprayed some WD-40 to lubricate the moving valve inside, shake it well.
I also cleaned the trottle body bore, as Kestas suggests here.
I have not had any stallings since then.
This worked for me.
Just my 2 cents.

Did you tell your mechanic about all the lights flashing on the dash before the car shuts down? I believe this clue is key to your problem.

Sounds like low voltage problems to me.
Check charge rate from alternator and battery condition.
Other than that, it could be one or more of many things but i would suspect the speed sensor in the instrument cluster if you perform all the other tests (air-flow etc) and find nothing.
Oh, you might like to keep your duty cycle meter on all the time and see if a constant voltage fault code comes up when the engine stalls.

Overvoltage protection relay can be bad too, this causes an intermittant loss of current to the idle control valve, and it closes too far. Worse if it is also dirty from leaking hoses.

Check vac lines and idle control valve hoses for leaks. Clean idle control valve and throttle mass air flow sensor venturi.

Have mechanic check the OVP relay -- if it is the original one with one fuse on top, it is likely bad, and will cause the ABS light to come on randomly, too.

Peter

Thanks all for the reply. But where are all these things you guy mentioned? And what to start first?

The OVP is behind the battery. It's a tall square unit. If the last four digits of the part number are 52 45 and it says "Made in Austria" replace it. The 52 45's are known trouble-makers and I suggest replacing them even if all is well with the vehicle. It's only a matter of time before they go bad. It's easy to replace for a DIYer. If the last four digits of the part number are 67 45, you have the updated OVP and just check the fuses.

If you need to find the throttle body, then perhaps you should get yourself a publication like Haynes that has a lot of good information with illustrations.

My question would be was it doing this BEFORE the $700 repair? If not, I'd be suspicous of something that took place while it was being serviced.

I never had this problem before the transmission service at all. I am still thinking something got loose or damaged while they are dong the repair work. But what could it be?

Intermitant stalling can also be a fuel pump relay -- you don't notice it when driving because you only get a very short loss of power before the fuel pressure comes back up, but at idle the engine stalls.

Most likely a big vac leak and a bad OVP relay.

Peter

Battery/alternator/ground connections are the easiest to eliminate as the cause. Simply remove connection and clean contacts with a stiff brush dipped in baking soda/water paste. Rinse the terminal and replace.