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My car is a 1992 Benz 300SE W140 Automatic Transmission, whenever i start the car and put it on D, when i step on the throttle nothing happens (the engine rpm does not increase) then after 1 second it suddenly accelerates normally until you have to stop at another intersection and the Engine RPM drops to idle, trying to accelerate, nothing happens again then suddenly accelerates.

This occurs until i get the car up to proper engine temp (around 90c) then the problem doesnt happen anymore, until i shut off the engine and restart again...

Could it be a transmission issue? (but when i step on the throttle nothing happens, not even the engine rpm increases then after a second the engine rpms go up and the car accelerates)

or could it be a fuel delivery issue? fuel pump? clogged lines? or could it be the MAF?

thanks in advance

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  • I recently had some work done on the car, the fuel hose from the tank had cracks and was leaking gasoline so i had that hose replaced then this started to happen.
    – bose
    Mar 13, 2019 at 6:14
  • Also, i checked the transmission dipstick and the ATF looked pristine and did not have a burnt smell/appearance and was exactly on the max line.
    – bose
    Mar 13, 2019 at 6:16
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    Welcome to Motor Vehicle Maintenance & Repair! To my thinking, this would not be an issue with the transmission, but rather something on the engine side. If it were the transmission, your engine would still respond when you press the pedal. It may have to do with the throttle position sensor (if it has one), but no real way to tell at this point. Mar 13, 2019 at 10:34
  • Possibly an air leak somewhere.
    – HandyHowie
    Mar 13, 2019 at 10:41
  • @Pᴀᴜʟsᴛᴇʀ2 I was under the same impression, the transmission pulls hard and checking the ATF, looks brand new and no burnt smell/appearance. If it were slipping tranny, when i step on the pedal the engine rpm should instantly rise and no acceleration. in my case, stepping on the pedal, no engine rpm and no acceleration
    – bose
    Mar 13, 2019 at 13:25

2 Answers 2

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I am happy to report that I've found the solution! (although with a caveat)

There was a malfunction in the MAF, there were no faults being reported thru Mercedes Star diagnostics to indicate that there was an issue.

It's very difficult to purchase even a reconditioned MAF for the W140, I tried several used MAFs and all of them were causing severe hesitation when accelerating after a cold start.

But I did stumble upon a quick hack, leave the broken/intermittent MAF installed (due to the distance between the air filter box and the intake) but unplug the wires connected to it. The car ran like a CHAMP!!

Although Star Diagnostics was reporting the missing MAF in its test results.

I've had the MAF unplugged for more than 8 months now and there was no change in fuel consumption, there was no change in the way the engine operates, in fact, it actually sounds really good (as compared to running with the broken MAF, the car drove and sounded lethargic and wanted to just quit at times)

So there you go, I'm answering this just so that future W140 owners might find this information useful.

Even though the W140 is a very old car (30+ years), it still looks and runs great.

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  • Great. Why didn't you try aftermarket MAF. There are plenty available from China and United States. Unplugging will work, but it will hurt engine dynamics. Have you owned the sedan since 1992? Your fix is not a fix, but rather a hack, which will put more load on the engine. Fuel efficiency would be hurt minorly so you won't sense much here. I've had 15 years of ownership experience on Honda, Mercedes-Benz, Audi and Jeep. And frankly this will ruin the fuel mixture and put more strain on the fuel delivery system in the long run. Be prepared for a new bill. Mar 2 at 5:06
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    for this particular model, not even pelican parts have it available. I have tried sourcing out refurbished and used ones... all of the ones I tried caused severe hesitation... tried cleaning the MAF sensor, still doesn't work. I'd rather have the car running than it sitting in a garage.
    – bose
    Mar 2 at 11:12
  • trofom, has quality maf available over ebay for w140. We had this imported from usa, and it worked for our uncle's w140, owned since day 1 of production. Mar 7 at 9:13
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Buy a new Mass Air Flow sensor from China or United States. Your answer is not correct to unplug the MAF sensor power/data line. Anyone out there should source the correct MAF new aftermarket. Removing the MAF will have consequences on the emissions and pollute the environment.

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