Hi all, i have been having a problem with my 92 300d 2.5 since i have had it (jan 2014) and it has gotten progressively worse since. The engine starts, misses for a bit then once it gets going stops missing but still has the loud diesel clatter until it gets to temperature. with it 90 degrees here today the preglow light stayed on for about 10 seconds.

Things i have done:
replaced glow plugs (today) and reamed the holes with the kit from mercedes source.

a few months ago replaced nozzles and pop tested to within 20ish psi

all new vacuum hoses, fuel lines, return lines, and fuel filters, except the clear fuel lines. they are on the to do list.

verified 12.3 volts at the preglow relay on each of the 5 pins.

what's next?

__________________
'92 300D 2.5
'99 E300TD

I'm not familiar with the 90's cars but with my old W123 240Ds, doing a valve adjustment worked wonders for getting them to run smoother when cold. When i first bought my '77 240D it needed constant pressure on the gas pedal after starting for about 3-5min or it would kill and it shook like it was gonna blow! after a valve adjustment is starts right up and doesn't need any throttle to keep it going. runs waaay smoother

I'm not sure if valve adjustments are applicable to your car, but if they are then maybe give that a go.- I'm sure someone who knows more will chime in here in a minute...

__________________
1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k