1972/3 450SEL sputtering on acceleration

[smoothbnzf4n4tc]

Okay guys, I have a green 450SEL and it's my baby. A month ago, the car started giving me a lot of problems specifically under acceleration. The car seemed to sputter around 2000-3000rpm and at gear changes. I took it to the dealer and they suggested that the throttle switch is the problem. They replaced the throttle switch and for a while it seemed to get better. however, the problem returned a week later and now the car is almost undriveable, with almost no power and sputtering sounds coming from the engine that weren't there before. Also the power if very irregular. I'll press depress the accelerator and the car doesn't respond at all. I'm not a mechanic so I don't want to interfere with what the dealer says, but they still don't know what the hell is wrong with the car. I'm getting quite angry that my baby hasn't been fixed yet. Do you have any suggestions as to what could be causing the problems?

[Big_Richard]

being D jet, the first thing i would check is the manifold pressure sensor. These are the kinds of symptoms the engine has when its diaphragm fails. These items are ludicrously expensive, so try out a good second hand one first before buying one. Someone will supply you with a picture if you ask nicely

[oscar]

Hi. I find it hard to believe that the TPS (throttle postion sensor) could cause the car to become undriveable but its amazing that you say the problem went away when it was replaced initially.  There may be more than one problem occuring here. So two things to do.

1)  You can disconnect the TPS by pulling its lead and if its faulty, the car will run very smooth in comparison.  Even though you got a "new" one, it still might be defective.  The TPS is like an accelerator pump and whilst you'll loose some take off power it should accelerate smoothly.

2)  My first thought regarding the spluttering and then getting worse is exactly what Pat says, that your MPS (manifold pressure sensor) has failed.  Once that copper diaphragm inside cracks the car will run like a dog.  Look here

3)  I'll throw in a 3rd suggestion.   Do you trust the mechanic?  You say "dealer" I reckon you should seek out an independant MB mechanic.  I know there's the odd dealer around that might be passionate about the classics and if you find one, good, but you're more likely to find someone fluent in d-jetronic at an independant.

Where abouts in the world are you?

[smoothbnzf4n4tc]

Thanks for the replies guys. I will let my dealer know. Right now it's still in the shop. I live in the USA, California specifically.

[smoothbnzf4n4tc]

As to whether I trust the mechanic/dealer. I have always brought my cars to them, but unfortunately I must say that the same old people haven't stayed. As the newer cars come out, most of the older generation who knew my car, have moved away or retired, even though I've stuck with the dealer.

[oscar]

There's a few guys on here from Ca, I'd see if there's other recommendations.  Without knocking your dealer, that's the prob with some of them that the guys that cut their teeth on 60's and 70's mercs are retiring and the mechs that work on the cars are more familiar with more recent models. 

Anyhow, at the very least, ask the dealer to check the MPS to see if it holds a vacuum for starters.  Try and source a used one if it doesn't hold a vac, since they're up towards $1000US plus for new.  $100 or less 2nd hand. 

[jbrasile]

smoothbnzf4n4tc

If you are in Southern California and want to try another shop, go to Pete's Autohaus in Torrance, they have very good experience with these older cars 310-320-3033 I have been taking my 1980 450SEL to them for some time with great results.

There is also the Mercedes-Benz Classic Center in Irvine, but I am not sure how busy they are right now, certainly worth a call to 949-598-4842, speak with Tom Hanson and tell him Joe Brasileiro suggested you called.

Don't take your car to a main dealer unless maybe to Silver Star in Westlake Village who used to have a very good tech named Steve (not sure if he is still there)  who knew these older vehicles quite well.

I would agree that that MPS seem to be the culprit.

Regards,

Joe