FQ:

I have a 93 300e 2.8 and have had a similar problem with starting when temp is below 20 F (it would take 2 or 3 tries to get it going). Also experienced every so often when the engine is still warming up, a lag in acceleration when gradually depressing the pedal at lower RPMs. Aside from that it runs like a charm. I've been living with this for the past couple years because it was just a minor inconvience. But this past weekend with the record cold was the first time that I wasn't able to start the car. Would crank the engine but it was just not catching.

Had it towed to my regular independent MBZ mechanic and he said that the engine was flooded and thought that the injectors may be leaking. He didn't think it was an OVP, fuel pump relay, throttle actuator, or fuel pressure regulator problem. Harness has been already upgraded. He suggested using some injector cleaner to see if it helps, but the next cold morning, he also couldn't get it started. He found a tech bulletin for this year/model that describes hard starts below 5 degress C with no fault codes. The bulletin recommends replacing the HFM-SFI module ($$$) with one with upgraded software. He said that the plugs looked like the engine has been running rich which also is described in the bulletin. Its a shame there isn't a more conclusive diagnostic available for this expensive part. I'll keep you posted if this solves the problem.

Steve