A little background / history on my car, and description of the current issue.

I have a '93 190E that has been changed over to a 5-speed OM602 Turbo diesel. I've been driving it for somewhere in the neighborhood of 5 years, mostly trouble free. I "know" the car pretty well, having owned several other W201 Benzes, and I'm the guy who put this one together.

Anyway, lately, I've been having a consistent issue at highway speeds. I can be driving along on the interstate, typically in 5th gear, and as I approach 2500 rpm's, I can feel the turbo start to "kick in", I can hear some turbo whine, and definitely feel that the car wants to accelerate. It will pull pretty hard at this point, and continue to accelerate from 2500 rpm quite readily. This is roughly 70 mph, with 3.07 rearend and 225/50/16 tires on the back.

The issue takes place as I try to gently let off the accelerator pedal. As I lift off the pedal even slightly, it's like the power completely goes away, no matter how gradual or smooth I am with the pedal. It kind of has the feel of a cruise control that only has an "on" and "off", or as if the car has a very sticky accelerator linkage.

This has only recently started happening, but it's pretty much 100% of the time now.

I don't think the problem is in the linkage, as I inspected the linkage, greased everything up, and confirmed that the linkage itself is not sticking. At lower rpms or "around town", I don't notice this issue.

Before I dig in any deeper, I'd appreciate your thoughts on the most likely causes. I don't know whether this is more likely to be an ALDA issue, a wastegate issue, or an internal IP issue (I really hope not).

As always, any suggestions would be appreciated.

Steve

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

Hi Steve,

Personally, I would start with an inline pressure gauge b/w alda and turbo. Highway loading is very different than in town loading (higher boosts etc) which affect the supply to the alda. If something is leaking on that line, now that its colder, you could see a quick drop in fuel supply - my current thoughts just to start.

Has the wastegate been modified?

Hows the plumbing and linkage (on wastegate) etc..?

I will be thinking about this the next few days and add more thoughts.

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