'97 SL320 stalling when coming to a stop issue
 

Tried a good fuel pump relay and it did not make any difference. Otherwise the car starts, drives and runs out fine. It will starts immediately after shutting down like this. There is never any issue if it is up in revs. Is there any particular area on this chassis (129) that the wiring sometimes has an issue in regards to shorting/grounding out? I did note that the battery is undersized for this application. The battery terminals/connectors look good and are tight.

I'll get the diagnostic hooked up to it over the next day or so and see what I come up with.

How about cleaning (scrubbing) the throttle housing & butterfly?
Many times that will cure that type of problem.

thanks
 

I took a quick look at it yesterday and thought it looked pretty clean but will go ahead and clean it properly. It looks like the car was taken very good care of at one time and then someone kinda let it go downhill. Now the current owner is "bringing it back to good nick".

It is very important that the correct portion of the throttle body is cleaned. The edge of the throttle blade and the bore where the blade is at idle is critical.

just throwing this out there, might not apply: does that model have a lock-up torque converter? i had a similar problem with a nissan once; it wouldn't unlock the torque converter and stalled the engine at a stop. it was something electrical though causing it ( can't remember what it was, sorry)

Take a good look at the throtle linkage. Inspect rollers and pivot shafts. Check to see if you have a throtle closed position micro-switch on the linkage. If you have the switch, check it for good electrical contact.

Just for accuracy, the 97 has drive by wire throttle. The throttle cable goes to a pot box on the left fender and the throttle is controled by a servo motor. ( Near as I can tell it does not have a clutch like the older mechanical / electrical throttle blade. )

Installed a new MAF sensor and it seems to have resolved the stalling. I guess stalling when coming to a stop is a symptom of a failing MAF sensor? I'll probably still go ahead and clean the throttle butterfly.

Did you do a diagnostic test or CEL reading? Was it throwing a CEL?

Interested because my earlier 300E has similar issue, obviously a different injection and OBD system but can't hurt to know the root cause of the issue.

I did perform diagnostics on it and performed a few test. Most notable was the slowness in the reaction time of the O2 sensor. I had already changed it out. I did not see any indication that the MAF sensor was amiss during diagnostics but maybe I was not focusing on it very closely. There were numerous fault codes when I initially scanned the car.

It looks like, at one time, this car was well maintained but over the past few years it has gone downhill in that regard (see it all the time). Someone has removed the bulb from the CEL indicator so the only way you know you have a code is to hook up the diagnostics.

I'll be changing the brake fluid on it tomorrow along with checking out the refrigerant side of the a/c. After that I'll try to get the diagnostics back on it to see what is showing up now.

For cars in general, some systems substitute synthetic values for failed components however, when the data is viewed on the scan tool it looks believable.

Using a late 80's Chrysler mini van as an example: The coolant temp reading through the scan tool looked OK, but if the temp sensor voltage was read through the scan tool, it would drop out for minutes at a time. Same drop out occurred when read directly with a volt meter.

This is turning into one sweet running car. In addition to the stalling there was substantial lifter ticking noise. Did an oil change using synthetic and running it harder than usual and it is starting to quieten right down. About all that is left is to install the new compressor/dryer and the front main seal and this car is ready to use as a daily driver. It is a good running car and I don't think the guy paid much more than around $4 or $5k for it:).