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mafiose 11-27-2003 01:45 AM

SOS...SOS!!!help!!Please read..advice needed ASAP!
Hi there I have done some search, they were very informational but not case specific. PLEASE READ......this a really good and very well explained case....

I have a 1996 C220 with 74K miles, 3 days ago while on the freeway at regular steady speed, the car experienced a drop in RPM, and came back on in a matter of 1-2 seconds (did not shut just a loss of RPM), then it happened again but this time 3 -4 times in a row and stopped. (mind you that so far I have no service lights or check engine flashing). The next day,when I was a surface streets, I would notice sudden drop in RPM about 1500 then back on, and it wiggles on and off....power ..loss....power loss....then runs good for 10 minutes ..then it happens a couple of time...until on a light it happened anf the car shot off.....turned it back on ...and arrived home.

That night ...I changed the spark plugs (just because I had extra ones) and was checking the wires anyways.....wires are fine...everything connected and in place. Finished my work and inspection....turn the car on ....went for a short test drive ..and called it a night!!

Next morning before going to work I turn it on to warm it up....first thing i felt is that it did not idle up to 1000rpm ike it normally does and stayed at about 500..and therefore the car was a bit vibrating (just a bit).....20 seconds shuts off......Turned it on .shut off right away in 3 seconds..when i turn it on and rev stays on but as soon as i take my foot off the pedal...2-3 seconds it's off.

By the way it turns on in a snap, the problem is keeping it on.

First. Do I need to clean my Idle ? where is it? pics or diagrams would help.

two. 3 days prior to this occuring I had a tensioner shock come i had crazy vibration of the engine and tensioner...for some while until I got it to a shop and fixed it that day....possibly related, could the vibration have damage anything in there????

I checked all the records on the car...there is no evidence in the paper that fuel filter change was ever done.....and it has been always serviced at the dealer by the previous it possible that they have missed it during regular service.....visual inspection of the filter ...reveals a dusty, greasy indication it has been changed anytime least it seems??? I am changing the filter tomorrow....does anyone think that it is a good candidate for the problem.

I hear no buzzing or humming from the fuel pumps.....

It might be the fuel relay...but who knows...IS THERE a way to check it or test ...and what is it?

I doubt it is an electrical problem does not feel like it is....because the symptoms are not sudden....OVP is ruled out....and I believe wiring is in excellent shape on the car.

I did have a code 441 a while back ...which is realted to purge flow, which has not come back for 2000 miles after resetting the computer ( I think it was due to an untight fuel cap).

Oh one more thing.....any advice on how to change the fuel filter far as techniques and steps...???

I really would welcome some educated and well established analysis on this issue. And advice is great

If you have any questions please ask.

vinamg 11-27-2003 08:27 AM

Sounds like a bad cruise/throttle actuator.


stevebfl 11-27-2003 09:45 AM

sounds like a single cyl misfire maybe increasing to multiple.

Unfortunately, nothing is easy to test without a competant scanner. with a scanner you could verify which cylinder was working either through misfire counts or through injector activations. In injector activations the injection is cut one cylinder at a time to see the resulting roughness occuring. With a 4cyl its is significant on each cylinder except the one that was misfiring.

Once the light is on then the cyclinder will be IDed by an OBDII scanner. The above functions won't be available with only an OBDII scanner.

abe g 11-27-2003 12:53 PM

hesitation when engine running, surge, then drop rrpm
First thing to look at is fuel filter. This sounds classic, if fuel pump runs, filter clogging will give you these symphs. Good luck Abe G Before changing filter run some techron through this wi;;stir up addittinal gunk thta filter may trap. Then replace filter.

Dan Smith 02-13-2005 10:56 AM

This is not as easy as it sounds. This is a computer controlled Benz, correct? While I am not fond of such, we are forced to deal with them. Our ML 430 did a similar thing. Turned out the computer reading machine indicated a "fault". I think our mechanic called it that. The fault was caused by me. I once opened the gas cap while the ML was running. How stupid is that??? You wouldn't believe the problems we had untill I brought it to my own tech that does the vast majority of the repairs on a real auto, the 6.3. The dealer couldn't find it when it was towed in the first time. How's that? Nor the second time , when driven in. My mechanic asked a huge number of questions. When he asked about the gas cap he just smiled.

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