Intermittent stalling, RPM drop, misfiring...oh boy

So it wasn't the OVP.  I replaced that with a brand new unit and the problem persists.  To refresh, here's what has been plaguing my 300e. 

Very intermittently my car loses RPMs and stalls, but ONLY under load.  This first happened once in a parking lot after warming up, then again in the driveway.  Not too long afterwards, I parked the 300e for a bit since I didn't have a place for it, and it now does it about 40% of starts.  It is fine when cold, but after it warms up, the idle becomes rougher and as soon as you step on the gas a bit (still in park) it misfires and shakes badly up until about 2500 RPMs.  However, shift it into drive or reverse and it does the same misfiring but the RPMs drop until it stalls.  I thought it was the OVP since that is a very common replacement item, but no luck.  Also, during this time I found that my EHA valve (stands for electrohydraulic actuator) began to leak massively.  Again there was a glimmer of hope, but even after replacing it with a known good part, the problem persists.  Actually, I might as well just list all the stuff I've checked

- replaced ovp with new unit
- replaced cap and rotor, just inspected them again today to see if there was anything wacky there...cap had some usual corrosion on contact points but nothing out of the ordinary
- replaced wires, checked again for arcing today and nothing
- replaced EHA (was leaking wildly, had to be done anyways)
- checked engine temp sensor, appears to be fine
- checked the flywheel crank sensor (which goes to EZL), came out to 880 ohms, which is well within spec
- replaced O2 sensor
- fuel pump is always on during this so that rules out FPR
- replaced spark plugs (proper style - ordered from here)
- checked vacuum connections, seems fine
- duty cycle (checked via X11 diagnostic port) remained within 47-51%, which is very good--Lambda tower does not need adjustment.

Really not sure where I am heading from here.  I think I am going to replace all of the vacuum lines that I can find and hopefully fix any leak that might exist.  Stay tuned....

The plot thickens...300E stalling

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).

Introducing myself

Welcome to the ranting of an over-zealous Mercedes owner and DIYer.  Seems like every day is a new adventure with these cars, working on them and driving them.  Many of my posts will DIY related (anticipate much cursing after mishaps) but anything surrounding the automotive world, specifically MBs might appear here.  Just to make it clear I have absolutely no affiliation with Daimler Mercedes Benz, MBUSA, MBNA.  I'm just an owner and fan tryin' to live day by day.