126 odd start

[mbtjc]

My 126 is starting in a manner that it hasn't done before. A little background. Been suffering from the classic rough idle for a while...took it into my tech (been working on MBs for 30 years)...made some adjustments to the CO, and put in a hotter set of plugs...he said that the thing that really needs to happen is a cleaning of the top end, which he says they have an $11,000 machine to do that...I'll do that when I get the time and money. For the time being...the idle is still a bit rough, but not near as much and not near as bad as before. Very livable and satisfied until I get that cleaning done.

Here is the deal though. Here lately (about 1-2 weeks after getting it back) whenever I start it...it "chugs" when I start it and then runs fine. It's kind of like a carbureted engine when idling and you punch it really quick and it bogs down and then comes back. It has never done this before...even before with the worse idle. Any ideas??

[mbtjc]

Anyone?

[mbshop]

what has really been checked? not enough info.

[mbtjc]

Ok, well here is the rundown: Replaced: Oil, filter, plugs, timing chain, guide rails, belts, motor mounts/shocks, coolant (MB)....and I think that is it as far as things pertaining to the engine. Ran great, started like never before after the new chain (good way, didn't hardly crank, just fired up)....ran great for a while, classic rough idle again though, but still started fine. Took it into the tech asking him to "tune" the engine, make sure everything checked out and seeing what he could do about the idle. The CO had already been adjusted up previously and he said that the current plugs were not hot enough to burn the extra fuel. So he adjusted the CO again and then the put in a hotter set of plugs (Bosch copper). Ran awesome when I got it back. Very slight bad idle....very pleased with the improvement. This is where he said again that the only way to really make it run well is to get the top end cleaned out and re-adjust the CO down. But anyway...ran fine....then like a said before a week or two later it's been having this "chug" when starting, which it has never ever done before. The idle is a liiiittle rougher than when I first got it back, but not much. But the idle here is not my concern....it's the start.

[mbshop]

ya need to have your fuel pressures checked cold and hot.
before this, get another mechanic that knows this system.
needing hotter plugs to burn the extra fuel tells me this guy
has no clue. stock plugs are more than adequit. do not use
platinum in this engine.
a c.o. tester can tell you if you have to much gas or are having
a lean miss problem.
are the plug connectors ok?
on and on. get a new mechanic first that knows mercedes.

[mbtjc]

These are not platinum....just Bosch coppers. Apparently this guy has been working on Benzes for 30 years...

Yesterday it seemed to have gotten worse. It also seems to be worse on a cold start than a hot start...or if it has been sitting for more than just a few minutes. Yesterday when I started it cold, it acted like it wasn't going to turn over, then when I let off the key it "chugged" really bad and then came to life so to speak. If it is having problems keeping fuel pressure in the lines, what could be causing this?

[mhingram]

Tell him to test your coil. If he does not want to buy one they are about $100 -150. I had a similar issue bogging down on hard acceleration from start and slightly rough idle but otherwise fine.