70,000 km / 45,000 miles on the clock, service up-to-date. Daily driver and a great ride.

Starting few weeks ago, car would occasionally (about once or twice a week), have difficulty with cold starts:

- engine would not catch on 1st crank, then start up as normal on 2nd crank;

- engine would catch on 1st crank, but stumble then surge for a sec. The surge takes the rpm to about 1,500 mark (normally should be around 1,000 ?), before settling down to the usual idle speed.

No Check Engine Light at all, and the car otherwise runs fine.

Warm/hot starts are always good, one crank.

What may be the problem ?

Throttle Actuator (big $$$) starting to go bad ? Or something minor to leave alone for now, taking it to the shop if it gets more frequent ?

Thanking in advance.

There is a tech service bulletin which may be applicable. Text is as follows:

03/95-2 M104 WITH HFM INJECTION SYSTEM


In case of customer complaints of high idle (approximately >2200 rpm) for a very short period of time (< 1 second) immediately after cold start, an updated EA/Idle control unit is available from our PDCs. The updated control units can be identified by a software production date of "SW 43/94" and higher stamped on the housing in the area of the barcode label. The following control unit part numbers are affected:

Electronic Accelerator Control Units

Part No. 124 545 65 32 - E320
129 545 05 32 - SL320
140 545 49 32 - S320
202 545 01 32 - C280

Idle Control Units

Part No. 124 545 55 32 - E320
129 545 19 32 - SL320
140 545 52 32 - S320
202 545 43 32 - C280

Thanks to J.M. for the detailed response.

The symptoms have changed since my original post, now not quite mapping to the bulletin that J.M. kindly clipped.

Current situation

1. cold starts - normal

2. hot starts - normal

3. warm starts (say more than an hour after shutting down but before engine completely cools) - 1st crank engine spins but does not fire up. 2nd crank engine starts, stumbles, rpm shoots up to about 1000-1500 for a sec, then settles down to the normal 500-600 range.

The car otherwise drives well as always.

Read in the archive that OVP & Throttle Actuator are common failure items on the W124 / M104.

The OVP is easy to replace DIY... but if it is really the culprit will engine crank at all ?

I won't be able to replace the Throttle Actuator myself, but as it is a big $$$ item would like to know if this is something that is possibly at fault here.

Thanks again for all advice.

Sure...OVP has nothing to do with starter circuit.

Any chance you can build the "Radio Shack" code reader tool described on this site? It will be very difficult for anyone to help you without some more diagnostic information. Also, has the engine wiring harness on this vehicle ever been replaced?

Thanks again for the tip J.M. Engine wiring harness replaced in 2003.

I wouldn't be able to build the code reader based on my current knowledge levels (and not much spare time available to train up).

The starting problem has grown more frequent now, happening daily with hot or warm engine. Only cold start is good.

Will be taking the car to the shop & post back on the remedy. Hopefully it's not the throttle actuator. Cruise control works fine all along.