300E with cold-startup problems/low idle - PeachParts Mercedes-Benz Forum

pawoSD · #1 11-22-2008, 10:26 PM

My newly purchased 1990 M103 300E apparently doesn't like to start cold....it takes either one long crank (8-10 seconds or so) then it begins to catch and finally manages a low idle (around 450-500rpm), you have to let it sit doing that for a couple minutes, then you can give it throttle and drive etc....giving it throttle right away results in it just stalling/shutting back off.

Also, about 60% of the time when just using it/driving around it settles in a very low idle, like 500-550, it never stalls out, but it does quiver a little. Obviously this idle is too low....sometimes it will come back up to about 600-700 and stay there, other times it goes lower. Playing with the throttle in park, giving it little nudges up to 1200 or so then letting off, it goes down to 500 then rises back to 600...seems normal, and it idles very smooth and starts ok when warm.

When at idle with no throttle applied shouldn't the economy gauge be all the way pegged to the left? It hovers about 3 needle width's towards the center. This means leaky vacuum tubing under the air cleaner right?

The air cleaner assembly isn't held in place very well, one of the mounts is missing and it moves a little.

What things should I check? Idle control valve? Tubing? The exhaust smells like its running a bit rich/a bit of unburned fuel. Its clean though, no blue or white or anything. Coolant is clean, oil is clean. Pickup is very good once its been running for a few mins, it takes off VERY quick, and pulls very strong/rev's way up just fine. Its just that annoying low idle and cold start!

It will cruise at 75 on the freeway with the cruise control on smooth as silk and steady. So the ignition/injection system must be ok.....

Help?