Engine hesitation under light throttle
 

I have a '97 E300D and yesterday on the Interstate I was cruising at 55 MPH when the car started to buck. However, if I was coasting or the engine was under a load the bucking would stop.

I thought maybe there was some water in the tank so I put in some Diesel 911 but the problem persists.

Any thoughts?

Thanks,
Andy

I would suggest, that if it continues, you might want to check both fuel filters. If they show up as o.k., you might want to check the resonance flaps to insure that they are free to operate as designed. They can get gunked up with carbon which will stop them from opening and closing. The first resonance valve is supposed to open at about 2300-2500 rpms, and the second one is supposed to open at a higher rpm which escapes me right now. Good luck

On the 98/99 turbo models I would first check for air in the fuel lines. The surging/bucking is a symptom of deteriorating o-rings allowing air to be drawn in. This is a very common, almost universal, problem on the turbo cars. I've not heard of this problem on the non-turbo, but it's very easy to check. Start the engine, open the hood, and look at the clear fuel lines. Lack of bubbles running through the lines would be a good thing...

- JimY