Weird Symptom - PeachParts Mercedes-Benz Forum

tobybul · #1 04-06-2011, 10:25 PM

My 85D runs kinda funny.... when I accellerate it 'pulsates' as if I'm pressing down on the gas pedal and letting off and pressing and letting off. It just did it all of a sudden. I thought at first that maybe the tranny is slipping but It shifts fine. Its like it accelerates fine initially then as if theres a lull and picks up again.

Could it be air getting in the fuel line? Dirty fuel filter? Dirty injectors?

I did put a can of Sea Foam recently to try to help clean the injectors cuz its been kinda sputtering after I start. Its always been a smooth starting engine but kinda gradually started sputtering when starting.

I also washed the engine before this started happening. But I've always washed the engine before and never had this.

Maybe a diesel purge is in order? Any thoughts?

leathermang · #2 04-06-2011, 10:28 PM

You should not be using a gas pedal on your diesel....

tobybul · #3 04-06-2011, 10:37 PM

leathermag, I actually replaced the rusted out fuel lines of this car last year all the way from the tank to the engine. Its been running great since. This cars sits around a bit since I drive the 84D and my son who normally drives the 85 is away in school.

79Mercy · #4 04-06-2011, 10:39 PM

I would start with checking for air leaks in the fuel system then i would go to replacing the fuel filters, and then checking the strainer in the bottom of the tank if the problem continues.

scottmcphee · #5 04-06-2011, 10:42 PM

sounds like a miss on a cylinder, for any kind of fuel / delivery problem, or too-tight valve maybe

but are you sure it's engine related? do you have good flex disks, and your drive shaft center support in good shape? wobbly / loose wheel?

leathermang · #6 04-06-2011, 10:50 PM

I do believe in Diesel Purge..
but has this been happening OVER more than one ' place of obtaining fuel' ?
Perhaps you got some bad fuel... can you try someplace else close by before starting on the " fixes "?

barry123400 · #7 04-06-2011, 11:19 PM

Check the transmission fluid level carefully. One of mine surged when a quart low.

Skippy · #8 04-06-2011, 11:28 PM

I had a similar symptom in my '83 last month. The tank was full of fuel from March of '10, and a small percentage was biodiesel left over from the tank of B99 I ran in it a couple tanks before the last fillup prior to going in storage. I changed the fuel filters and the problem disappeared.

tobybul · #9 04-07-2011, 06:18 AM

I don't think it's the flex or drive system but I'll take a look this weekend. The tranny fluid is right on since thats the first thing I looked at. I'm thinking its fuel related like possibly the Sea Foam and Power Diesel I dumped in the tank (but that was days earlier), or possibly air or maybe even water in the fuel. Maybe one of the clamps around one of the fuel lines I put in when I replaced the lines came loose.

I did fill 'er up the other day so the tank is full but i haven't driven it far enough to maybe get rid of the fuel that maybe contaminated close to the engine.

tobybul · #10 04-07-2011, 10:22 AM

oh, the other thing i was wondering about too is if this is turbo related. Could it be that the turbo is kicking in and out?

vstech · #11 04-07-2011, 10:29 AM

Quote:

Originally Posted by tobybul

oh, the other thing i was wondering about too is if this is turbo related. Could it be that the turbo is kicking in and out?

I don't think a turbo can cut in and out like that. it could build and drop pressure, but it takes A LOT of time for this.
it certainly would not be a studder

vstech · #12 04-07-2011, 10:32 AM

... it could be, now that I think on it.
your washing could have damaged the wastegate somehow causing it to bounce open and closed...

Junkman · #13 04-07-2011, 10:37 AM

Probably not turbo but you can temporarily T in a boost gauge - easily. I'd bet fuel which would be the normal things ie filters, screen, look for leaks, notice any changes in the clear filter, perhaps reverse the hoses, Startron - all of the processes listed throughout the forum.

mike240dds · #14 04-07-2011, 10:45 AM

I have been learning for past few weeks that everytime I think i have a major issue with my car it turns out to be something simple. If the engine is surging and it has been getting worse gradually, I would check the fuel system first. Leaks, Dirty filters, dirty tank screen... Car has been sitting right? Eliminate the simple possibilites first.

tobybul · #15 04-09-2011, 09:45 PM

It appears the problem may have been the Sea Foam and/or Power Diesel additive I dumped in the fuel tank. There must have been a high concentration of the additive at the fuel pump at the time I expereinced the problem.

I didn't do anything to the car yet. Just drove it and didn't notice the symptom anymore. Today I went on a 2 hour trip and it ran fine. In fact, it seemed to run even better. Maybe, the additives cleaned up a bit of the fuel lines.

I don't think I'll be using either of those additives anymore.