w124 '87 300D lumpy idle and stutter
 

Hello all!

I haven't posted in a long time because my '87 300D has been really great and reliable. Maintenance so far for the last 4 years has been really easy. Shocks and things.

I've noticed in the last few weeks that the idle in the car is behaving somewhat strangely. It could be called lumpy or very slightly surge-y. Additionally - especially when the engine is cold - when I take my foot off the gas too quickly the engine stutters and then bounces back to idle. It can stall easily in this state if I'm not careful.

Once warmed up, these symptoms are still present but less extreme.

Power on the highway seems to be down, and I don't know if I sense the turbo spinning up and the power that used to come with that. Since my odometer is busted I can't check on the mileage very accurately, though it seems normal after a long drive. I wouldn't know how to test the turbo.

I can think of a bunch of things to check on, but I'm hoping for some Occam's Razor advice here in what to check or fix first that is easiest / cheapest / likeliest. Having some difficulty searching the forum for this sort of thing - though it seems common.

I'm going to swap the fuel filters and check the vaccum lines. Other than that I'm not sure where to go next. Hoping I don't have to rebuild the injectors or something complicated.

Thanks! I'm so glad this forum is still around after all these years.

Ben.

Fuel filters and vacuum lines first, as you point out. The potential for condensation in the fuel tank, especially in a cold climate, means frequent filter changes.