I have a 95 c280 that's been having some weird issues. We recently replaced the throttle body with a newer updated one. The plate on the original one wasn't shutting properly, and would stick open. After the change the car seems to be idling high. When in it's park it will sit around 1200 RPM, then drop once put in drive. Next, when you start to accelerate it's sluggish until it hits 2000 RPM, then it pulls harder. It's pretty much exactly at 2000 RPM every time. Another thing to note is that it tends to shift hard going up in gears, mainly from 1st to 2nd.

We've tried doing the throttle reset procedure, and resetting the ECU by disconnecting the battery. I also tried something I saw on a video where the person just turned the key to the on position for around 3 minutes and it's supposed to relearn the idle. Nothing seems to be helping. So far, prior to the throttle body, I've replaced the fuel filter, fuel pump relay, air filter, and spark plugs.

We aren't sure what's going on with it. Has anybody ever heard of it being sluggish until 2000 RPM, and does anybody have suggestions on what to check next?

Why did you replace it with a "newer updated one" (throttle body)?
Whose "we"?
Please elaborate.

After driving it for around 30 minutes, it would basically refuse to accelerate unless you floored it.

I don't think the "we" part is important to providing input, but the "we" was my dad and I.

ok. understood.
but you still did not answer the first Q.

and what is this "updated throttle body"?
just from the read, it seems you replaced it, but not with a stock oem part replacement.

The reason we replaced it is because of it not accelerating unless you floor it. We started checking things on the top half of the engine, and found that the throttle body plate wasn't shutting close.

That part, I'm not exactly sure about. My dad purchased it, but i believe it was just one from a newer M104 engine that had been updated after the issues they had with the ones before them.

Post #4 - https://www.benzworld.org/forums/w20...hink-99-a.html
Try this as suggested.

Okay I'll do that in the morning before I head to work and report back

So I tried this, didn't hear any clicks like one of other post mentioned, and it seems to be the same. Still doesn't really accelerate until after 2000 RPM. I tried flooring it at around 30 MPH today to see what it would do, and it didn't seem to downshift into the correct gear. For example, it should have went from 4th to 2nd, but it went to 3rd instead. Also, once it got up to 4000 RPM, it basically wouldn't accelerate anymore after that.

Scan and see what saved error codes, if any are stored. Post here.

Okay so it looks like P0505, P0141, P0327, P0411 are stored

P0411 - Air injection pump - need to test this air pump to see if it's doing its job of pumping air.
P0327 - knock sensor - it could also be the econo crap wiring harness that's the culprit.
P0141 - 02 sensor - could need replacing
P0505 - This usually relates to a throttle body issue and could be tied into the dreaded econo crap harness issue on these w202s in that era.