My 300E has 201K, and I have had it for five years. It has always had a "stutter" at idle.

A couple of weeks ago it began to miss under load at low RPM, and occasionally die at idle and then be difficult to start and refuse to idle. Then it would be fine for an hour or a day. This only occurs with the engine warmed up, usually just after the temp passes the 80 degree mark.

To fix this, I did the following:

- inspected all vacuum connections - no broken, loose, or cracked connectors

- checked vacuum: steady 19-21" at idle

- replaced the spark plugs with Bosch H9DC copper

- replaced the O2 sensor and verified cycling around 50% (needed at tiny amount of richened. Cycling at idle and 2500 RPM is about the same.

- cleaned the rotor and distrirbutor cap contacts

Following this, the car was running better than any time I remember. I drove the car a couple of hundred miles with no problem. Then tonight, I drove about 3 miles and was stopped at a light. Rough idle and died. Started hard. Drove to restaurant, missing badly at low RPM and very rough idle. Ate dinner (about 90 minutes), car was fine on way home.

Cap/rotor, plug wires, fuel and air filters replaced 20K miles ago. Fuel distributor is a rebuild and looks fairly new.

Any ideas?

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

What condition are the idle control valve hoses in? Mine were rock hard, and although they looked fine, were actaully loose on the idle control valve barbs, so that they were sometimes loose and sometimes not.

If bad, replace, and clean the idle control valve when you do -- when the hoses leak, it gets dirty, and will tend to be slow to respond, so that you get a stall when stopping quickly.

I'd also check the current at the EHA just to make sure it's working OK, too.

Problem is, whatever the cause of the stalling and hard start appears to be intermittant, so all the checking in the world won't give the correct answer if it isn't going on when you check....

OVP relay is also a commone cause here -- what happens is that the current flow to the EHA gets controlled by a bad connection in the OVP rather than the computer, so the mixture goes haywire. Quick diagnosis is to tap the relay (behind battery, the one with a fuse on top). If it immedialtly works properly, or gets worse, replace relay.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I had a similar problem with my 300 e turned out to be resister or suppressors on the end of the plugs that caused the problem, i replaced them and the problem now gone. Only one was crook and it would fail occasionaly, causing a miss and then engine fail.

I had a similar problem with my 300 e turned out to be resister or suppressors on the end of the plugs that caused the problem, i replaced them and the problem now gone. Only one was crook and it would fail occasionaly, causing a miss and then engine fail.