Its been a while since I've updated this because I have been unbelievably busy. School started up again and the 300E began to stall when up to temp. There are so many things that can cause the engine to stall out in this fashion, let me describe my circumstances:
First time it ever did this was in the parking lot of a local supermarket when I was out on a really quick grocery run. I parked the car (only had gone about a mile from my apartment), went inside, got what I needed and came back out in about 5 minutes. Starting up the car, it stumbled just a tad but seemed pretty normal idling. As soon as I put any load on the engine (so basically when I shifted into reverse) it immediately stalled. I was able to push it back into the space, start it up and idle it again. I popped the hood and didn't notice anything out of place...checked the OVP for any visible signs of fuse failure, and nothing out of the ordinary. I got back in and revved the engine a bit and noticed a misfire whenever I had my foot on the gas to rev it (would not misfire coming back down, only under a load). After about 5 minutes it fixed itself and I was able to drive home.
Second time was after I replaced a burst coolant hose. I was terrified that in the process I had blown the head gasket by localized overheating (though the car did not get above 110* on the gauge) and I was suffering from low compression. However I realized it was the same odd issue as I experienced above. I figured in the process of checking everything out under the hood I jostled some vacuum lines...I made sure they were all in their respective places, ordered a new valve cover-to-air cleaner tube and installed it. The problem went away after that so I thought I had fixed it
Now, I have parked my 300E at my parents' for the most part, until I can sort out DMV inspection stuff. I ended up buying a new car about a month ago since I needed something that would not break down at ALL, and would not cost me money to repair if it did (read: warantee). My dad calls me a couple weeks ago and told me how he went out to grab a sandwich from a local deli and the car died after he got back in. Oh great! The mystery lives on!
So far I have replaced the overvoltage protection relay (OVP) which is perhaps the most common failure in these cars at this age...did not fix the problem, but its good to have a spare OVP in the glove box for when it inevitably does fail so no harm no foul. I initially suspected the OVP because it intermittently fails (exhibiting the exact symptoms I had) before an ultimate failure. The signal and power for the engine computer goes through the OVP, which is the reason the car runs like crap upon its failure. My next culprit is the O2 sensor, which is a logical choice seeing as the car only behaves badly after it warms up, then the engine temp sensor. I'm going to have to spend quite a lot of time with my digital multimeter at some point, just have no idea when I am going to find that time, especially considering the fact that the car is a few hours away from me at this point and my semester is in full swing. Oh well, this is the reality of owning old MBs, its a labor of love. My 300SD is still inoperable due to a bad transmission too, so the only thing I have at the moment is my brand new car (which I do love).
