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Discussion Starter #1
Hi! Brand new user here, this is my first post!

I've been lurking on the site for a couple years, and I've been watching Kent's YouTube vids, and I finally in November got myself a W140!! This is my first Mercedes, and actually my first German car. I got the car for a song, as it had the entire right bank of idiot lights on, it ran very rough and shifted very hard, one window wouldn't close, and one door wouldn't open. The body is in pretty good shape, but some things just don't work as well as they could.

I got rid of most of the idiot lights with a 10amp fuse, I bought a new regulator to get the window up, and I haven't attempted to fix the door yet.

More pressing is the misfire on cylinder 1. I've done research, and I'm leaning toward the head gasket. And that hard-shifting tranny.

I just got another '96 S320, things work on this one that don't on mine, and vice versa. It's a perfect complement car: The engine and transmission work perfectly, and the body is pretty shite. It seems like someone tried to lower the front end, but it doesn't really look too good. Doesn't affect the ride much, other than making the steering feel looser than the other car.

There are many many posts on here about switching out engines for more powerful ones, but here's what I want to know:

How do-able is it to take the M104 and 772.5 out of one '96 and plop it in another '96 that had an M104 and 772.5?

I am not scared of getting greasy, and have spent many years messing around with American cars. I have rebuilt OHC engines, and fired them up without getting a check engine light.

But I have also had a guy that works on Japanese vehicles tell me that if I switch these engines it'll never run again! He said, "It's a Mercedes, not a Chevy!!"

What do the Mercedes guys have to say?

Thanks in advance,
-sg
 

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I think swapping a motor because of a misfire is a bit extreme. Why not correct the misfire problem? Have you pulled the spark plug on #1? Checked the coil? Have the harnesses and throttle actuator been replaced?

The other answer is swapping a motor from a 96, to a 96 is a straight forward project. Your friends advice about the car never running right is silly.

Fix the misfire.
 

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I had a different engine,from a older e class put in my 99. No problem.The other engine had throttle cable.Changed a bunch of things and sensors. Like this engine better less smog stuff
 

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Discussion Starter #5
I did pull the plug on the first few cylinders, and #1 seemed to be in much the same shape as the others, which lead me to believe it's firing fine.

The one receipt that came with this car was the previous owner having some shop look into it 'idling rough.' They replaced the spark plug wires before a tech noticed that cylinders 2, 3, 5, & 6 had low compression. Then they replaced a headlight bulb.

The way this car drives makes me very doubtful that this shop was telling dude the truth. I haven't checked compression yet, but it does rip roar around pretty damn well. Through my reading on this engine and the mess at the front of the block I am leaning toward the head gasket. But first I'm going to check out the fuel injector, see if it maybe isn't operating exactly as it should. I smell gasoline in the oil, and a friend said he had some other vehicle have that symptom and it was a fuel injector that wouldn't shut off!

Any thoughts on the transmission? Just swap it out, or is there a few things to try to get it shifting smoother?

Thanks again,
-sg
 

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Before I went swapping transmissions I would check a few things first. How is the fluid? Is it dirty or nice and pink? If it's all dirty, maybe a flush and filter change would help. When you have the pan off you could check for chunks in it that might indicate a replacement is in order. Also, what's the mileage on the transmission? If it is over 200k miles then it's probably nearly done. Other thing that can make it shift hard is a mis-adjusted kick down cable. This would make is shift late as well.

If you are getting gas in your oil then indeed it could be a leaky injector. My experience with Bosch injectors is that they are extremely reliable. I have never had to replace one on my Mercedes nor any of the multiple Volvo's I have owned. Also, if an injector was leaking, I would expect to see evidence on the spark plug (black and sooty if it was dumping too much fuel).
 

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Discussion Starter #7
I am bringing this old post back to life, as I have finally tackled the car and resolved the misfire.

(I see it's been two years, where does the time go?)

The misfire was indeed the coil pack. The electrical input side basically disintegrated as I unplugged it. Took me 10 minutes to pick the pieces out of the connector.

The car runs like a top now, especially with new non-gassy oil in it! Still shifts a little rough for what I think a Mercedes should be, and although the fluid itself seems nice and pink, the dipstick itself leaves grey on the rag. Do I flush and filter, or replace the dipstick, or both?

In hindsight, really glad I didn't just swap the drivetrain with the other car, as it decided to leave a giant oily pool of coolant on the back lane one day. I dipped a paper towel into the coolant reservoir and it came out black and sludgy. So the parts car was running better even without a head gasket! (When I bought it, there was a sticker on the back window reading, "It's not leaking oil, it's sweating power!!"
 
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