W202 Not starting

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A little update. Although after replacing the spark plugs, the car started from time to time I would get the rough idle just as before.

I tried cleaning the throttle body and replacing the fuel pressure regulator. No dice. Eventually, I replaced the MAF sensor. And all of a sudden - and much to my surprise, if not John Jones Jr's - it was purring away beautifully.

Many thanks to Jack at PCS for pointing me in the right direction.
Oh dear, back to square one.

To re-capitulate: it frequently idles rough and sometimes doesn't start at all. After it has started and the rough idle has died down all is fine.

I have changed spark plugs, HT leads, coil packs, the MAF, the fuel pressure regulator and cleaned the throttle body.

Things seem to be worse when it is damp.

What, if anything, can save this car from the scrapyard?

Weirdly, the thing that bugs me is not that it might be curtains for the car but that I don't know what the problem is.
What, if anything, can save this car from the scrapyard?

Weirdly, the thing that bugs me is not that it might be curtains for the car but that I don't know what the problem is.

What can save this car from the scrapyard is you admitting that you don't know what you're doing and leaving it for 2 hours to a reputable independent mechanic (dealerships mostly deal with new cars), pay the man a hundred bucks for some exotic sensor that looks like a butt plug, throw in a couple more for his cool beverage of choice, and drive away happily. Most of the threads I read on engine problems (and I read all of them here and on mbworld.ord) end up being either MAF or some other sensor. I don't recall a spark plug or a coil sorting itself out after warm up.

The thing that bugs me is that you consider taking it to a garage "risky", but you are perfectly fine spending a crap load of money beating the problem by replacing parts that are perfectly fine to begin with. At the same time - you said your head gasket went, but didn't mention anything about replacing it. You said your crank case cover is cracked, yet no word on getting that sorted. You top up half a litre of coolant regularly, and so no and so forth... You see the pattern?

And please don't feel like I'm attacking you. I think you've invested way too much in this already and don't want to just suck it up now. I've done this before and I know I needed a good slap in the face to stop being a moron.

Tackle problems one by one, starting with the known issues and eventually the culprit will reveal itself.
Took it to PCS. They believe that almost all my problems are caused by the head gasket. I had thought that they could happily leak away for years. But no.

The cost of having them doing the repair is to my mind prohibitive so that leaves a choice between scrapping the car or attempting the repair myself.
Symptoms are classic head gasket. In addition to head removal it will need skimming even possibly welding/pressure testing if corrosion/erosion has occurred. Doing anything less is throwing money away as your problem is likely to recur fairly quickly. Time to do your sums on the cars total value/ a recon or salvage engine/ head gasket repair.
Another point to consider is a "leak back" test on the injectors - it could be that one or more are dribbling into the chamber and flooding it.. hence rough idle on start up (eventually) .. can you get her to start with a squirt of damp start??
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Thanks for the suggestion. I had considered it but for everyone swearing by it there was another claiming it was the work of the Devil. And anyway, a lot of this is about the joy of ripping an engine apart.

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