Hi guys.. thanks for reading this post.

While getting ready for a long drive on Tuesday my car suddnely started loosing power. It did not just cut out but seemed to be losing running out of fuel (but the tank shows plenty of gas - I was on the way to the station to fill up though).

I managed to keep it running and got it turned around and headed back home. Trying to *test* the thing I applied more or less throttle, even shut it off once and restarted to see if it would reset. No joy.

I limped back at about 10mph. It was popping on throttle TB, like it was leaning out, not getting much fuel. Then after some time it started running near-normally again.. smooth, making power but still not 100%, then right before getting home it started acting up again.. but it did make it up the steep hill to the house.

At no time did any warning lights come on.. so I'm thinking it's not control/sensor related. Maybe when a sensor like the crank possition or something like that fails there is no light.. I just don't know.. :p

What I'm wondering (this car has 190k miles on it -- basically unknown history) is if this is a typical failure mode for a dying fuel pump or maybe a near tottaly clogged fuel filter.

One thing I did do was wash the car about 1 week before this (I'd not driving it since the washing) and wonding if this could be something as stupid as water in the fuel system...

Color me perplexed. Any input, trouble-shooting suggestions etc. etc. are appreciated!

__________________
-----------------------------------------------------

Car starts up fine and seems to idle OK.. but won't take thottle. I still don't get an ECU light. Only trouble indicator is the fact I can't drive it..

I'd hate to just start tossing parts at it without some logical diagnostic plan. Anyone have thoughts on some possible / likely culprits?

I would think the crank sensor failure would be complete. Or is that a dumb assumption to be making?

__________________
-----------------------------------------------------

im having stumble/ misfire problems of my own that i think are related to the oil- in- coolant- tank- syndrome thats known to plauge these cars. i think one of my plugs is fouled. i have run a bottle of fuel injector cleaner through (current tankful) to eliminate dirty injectors and the problems still persists.
car has less power than usual, and accelerates in a jerky manner, not in a consistent smooth manner like it used to.

im gonna see about changing the plugs, hopefully that will cure it as i cant afford major work right now. it probably needs a tuneup too.

anyway, i encourage you start with simple things like that,; fuel injector cleaner, spark plugs and so on before you throw parts at the problem.

there are lots of posts here about OVP sensors and MAP sensors and so on that also cause wierd running symptoms. do a search.
good luck. i will be watching this thread intently.

__________________
'O=00=O'
bmw 2002.
long live the legend

First place I'd look is the fuel filter. Even if you've replaced it recently. There has been a plague of bad gas running around.

__________________
'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.

I have not done the filters since we bought the car. I certainly should do that. Besides it is time for an oil change & analysis. Looks like a fun weekend ahead for me.. woo hoo!! :p

It would not be a heart-breaker if I had to toss a couple hundred at it to get it all up to snuff again. So far it's only needed rotors and a ball-joint since we picked it up.

__________________
-----------------------------------------------------

I recently had the same problem. I have a 91 300 4matic. It has 255,000 klm and I just had the engine re-built. To my surprise, the same thing happened. It felt like I was running out of gas. There was no power. I made it home and made some calls. After checking it over I checked the distributor because plugs, wires everything else was new. Took the Distributor cap off, unplulgged the wires and the rotor had fallen out. The three screws holding the rotor in place had come undone. If it was a couple of days or even weeks I would think maybe they were not put on properly when the engine was rebuilt but a couple of months....

It's very simple and not time consuming. It may take you a half hour. Just make sure the screws are secure.

Dist cap/rotor is on my list of things to check today... that's encouraging.. it would be nice if it was somthing that easy to address. I miss driving my *classic* W124..

__________________
-----------------------------------------------------

I am going to chip in, since I just experienced the same problem (it just came back, it happened before in January and "disappeared" by itself).

Driving along I-95 @ 85MPH, all of a sudden the car starts DECREASING speed even though the gas pedal is pressed. It catches on all by itself and takes off.
Sometimes I let it roll to a stop and it idles a little rough, or like crap.
Never had the opportunity to plug in the Duty Cycle meter until today, at exactly the time it happened. Fixed 92.3%

Since 90% is not assigned, the nearest fault is 95% DECELERATION FUEL SHUTOFF SWITCH (MICROSWITCH) which makes sense due to the symptoms experienced.

It feels like a rev limiter does not allow the car to rev up.
Does that sound familiar?

Anyway, I have not had time to check the switch yet, but I am quite confident that is MY problem. And it could be yours too.
I will update when the testing is done.

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

Awesome.. that sounds just like the symptoms I'm having. It's not 100% failure (although it almost died once). It was just putting 5-10 mph limping home and suddenly.. whamo... start running normally again! WTF?? Almost get home and it acts up.. putting/sputtering up the hill.. grr.

Today I went in and checked the cap/rotor. All nice and tight. Which does not surpise me because.. it looks like they are the 15 year old 200k mile old original parts! (see pictures).

So I ordered a new cap, rotor, cap cover and fuel filter from Fastlane. Looks like some fun next week. At least it was much easier than I recall to get the cover, cap and rotor inspected.

I don't know that the cap/rotor are my issue but regardless they are in DESPERATE need of replacement!

I'm wondering.. where is that decel switch and how difficult might it be to replace? Sounds all too plausible.....

Attached Thumbnails

 

__________________
-----------------------------------------------------

I just checked the microswitch, it is operating fine. DARN!!
It idles fine, but the Duty Cycle starts creeping up until it hits 92.3% and sticks there.
I disconnected the potentiometer, it started to idle high, but the duty cycle oscillated between 45-50% which is OK
I wonder, if the potentiometer is bad, how come I am not getting a fixed 40% even after disconnecting it?
When I test the pot, it tests OK too. What the hell?

Stevebfl, if you get to read this post, could you please share your thoughts?

I am not 100% sure the microswitch = decel fuel switch, but here is the picture. It is easy to find, it rides on the throttle lever.

Attached Thumbnails

 

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

WOW! That was FAST F-A-S-T FAST!

I ordered the parts on Sunday and they just arrived here today and I requested standard delivery service.

This is the second time I've ordered though the website here and I'm TOTALLY happy and impressed!! I wish all my internet purchase were this fast and smooth!

And I was planning to just side outside in the sun and smoke a stogie.. now I can do that AND fix my car!!!!

More info to follow...

__________________
-----------------------------------------------------

UPDATE

Well, that appears to have done the trick so the fuel filter goes on the self for another time.

Test drive was amazing. Car always had a slightly rought idle.. not that I expected more out of a vehicle pushing 200k on the clock but the cap-rotor disolved that and some other issues!

* tranny has always shifted very firmly (very) -- now it shifts like butter!
* would not downshift unless I really mashed on it -- now it downshifts with precision right at the moments I'd like it too
* felts a little sliggish of you apply full-throttle -- now takes off like a scaleded cat and revs right to redline if I'm really pushing on it.

All this just changing a cap and rotor!??! I guess the engine is firing better, running as well but requiring less vaccum and that might be causing the altered characterisits?

Hm.. really I don't understand it but on yesterday's test thrash (living out in sticks has it's advantages) it ran awesome.

MBZ, thanks for making a car that still drives like a champ so many miles later and thanks Fastlane/Mercedesshop.com for the FAST (quality) parts delivery! Now. if only you guys sold parts for my Ducati.....

__________________
-----------------------------------------------------

UPDATE

Been some time now.. car is still running strong. Occastional idle issue (I think there is a vaccum accy sticking somewhere time to time). 99% of the time it idles so smooth now that I have to check the tack to make sure the thing is still running.. Ah.. now that's the W124 character I remember!

__________________
-----------------------------------------------------