Diesel Forum Forum for Diesel engine vehicle related discussion
Sponsored by:
Sponsored by:

OM642 reduced performance after WOT

Thread Tools
 
Search this Thread
 
Rate Thread
 
Old Aug 11, 2025 | 08:19 AM
  #1  
charlesb2003's Avatar
Thread Starter
Member
5 Year Member
Photogenic
Liked
Loved
 
Joined: Oct 2018
Posts: 228
Likes: 41
2005 E320, 2008 E320 Bluetec
OM642 reduced performance after WOT

Just had the chance to take a nice long drive for the first time after completing my engine replacement (thread here) and I noticed that after full throttle acceleration for more than a few seconds that I would lose the ability to accelerate. I could still easily maintain speed, but throttle response was almost nonexistent. No check engine light appeared.

This happened twice: first time it happened was accelerating up a fairly steep bridge, second time was overtaking on the highway. Both were around 70-80 mph. Restarting the car after coming to a stop resolved the issue both times.

Any ideas what could cause this?
Reply
Old Aug 11, 2025 | 04:02 PM
  #2  
rapidoxidation's Avatar
MBWorld Fanatic!
 
Joined: Jan 2016
Posts: 2,749
Likes: 880
From: In the Shadow of the Tetons
2013 ML350 Bluetec
fuel filter
Do you have a computer you can connect and graph engine rpm/load and fuel pressure while running?
Reply
Old Aug 11, 2025 | 04:35 PM
  #3  
charlesb2003's Avatar
Thread Starter
Member
5 Year Member
Photogenic
Liked
Loved
 
Joined: Oct 2018
Posts: 228
Likes: 41
2005 E320, 2008 E320 Bluetec
Fuel filter was replaced when I did the engine swap, but I will see if my iCarsoft scan tool can do logging. Haven't tried that yet.
Reply
Old Aug 11, 2025 | 08:41 PM
  #4  
kajtek1's Avatar
MBWorld Fanatic!
15 Year Member
Photogenic
Liked
Loved
 
Joined: Jan 2009
Posts: 9,224
Likes: 1,798
From: V E G A S
1922 Ford Model T / no OBD
Typical symptoms for leak in intercooler system, who might show as oily residue around it.
The code triggers soft limp and if continued, it will trigger CEL.
Either way, coffee grinds are not the best for troubleshooting those vehicles, so better get a scanner.
Reply
Old Aug 11, 2025 | 11:36 PM
  #5  
alive19's Avatar
Member
Liked
 
Joined: Apr 2022
Posts: 136
Likes: 34
GL320 2007
Could be swirl flap valves?

Better to do a scan though.
Reply
Old Aug 12, 2025 | 12:42 PM
  #6  
charlesb2003's Avatar
Thread Starter
Member
5 Year Member
Photogenic
Liked
Loved
 
Joined: Oct 2018
Posts: 228
Likes: 41
2005 E320, 2008 E320 Bluetec
Can't be the swirl flaps, those are long gone.

I've got a brand new intercooler and one new charge air pipe. The other new one kept popping off (it's aftermarket, sadly FCPEuro doesn't have an OEM one for that side) so I went back to using the old one, which seems to have a small crack in it so I bet that's the issue. Hooked up my scan tool earlier to confirm:



Thanks all for your quick replies! I'm going to try fiddling with the clips on that new aftermarket charge air pipe and see if I can get it to stay on, I bet the old one is leaking thru the crack. It's a bit oily in that area.
Reply
Old Aug 26, 2025 | 08:11 PM
  #7  
charlesb2003's Avatar
Thread Starter
Member
5 Year Member
Photogenic
Liked
Loved
 
Joined: Oct 2018
Posts: 228
Likes: 41
2005 E320, 2008 E320 Bluetec
Got my new charge air pipe and it was definitely that. The old one had multiple cracks, I'm surprised I was getting any boost at all. Much less turbo noise (sadly, I like turbo noises) but WAY more power! Almost no hesitation off the line either, very nice!
Reply

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 


You have already rated this thread Rating: Thread Rating: 0 votes,  average.


All times are GMT -4. The time now is 03:47 AM.

story-0
6 Mercedes Models That Did NOT Age Well (But Are Somehow Still Cool)

Slideshow: Not every Mercedes design becomes timeless, some feel stuck in the era they came from.

By Verdad Gallardo | 2026-05-12 18:09:07


VIEW MORE
story-1
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun

Slideshow: Yes, Mercedes built manual cars, and some of them are far more interesting than you'd expect.

By Verdad Gallardo | 2026-05-02 12:36:58


VIEW MORE
story-2
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren

Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.

By Verdad Gallardo | 2026-04-29 11:19:28


VIEW MORE
story-3
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine

Slideshow: Before curves took over, Mercedes mastered the art of the straight line, and some of those shapes still look right today.

By Verdad Gallardo | 2026-04-25 12:05:49


VIEW MORE
story-4
Flawlessly Restored Mercedes 190E Evo II Heads to Auction

Slideshow: The 190E Evolution II shows how a homologation necessity became a six-figure collector icon.

By Verdad Gallardo | 2026-04-22 17:53:47


VIEW MORE
story-5
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know

Slideshow: Mercedes is turning one of its core nameplates electric, and the details show just how serious this shift is.

By Verdad Gallardo | 2026-04-21 13:58:06


VIEW MORE
story-6
Mercedes EQS Gets A Major Update: Everything You Need to Know

Slideshow: Faster charging, longer range, and a controversial steer-by-wire system define the latest evolution of Mercedes-Benz EQS.

By Verdad Gallardo | 2026-04-15 10:35:34


VIEW MORE
story-7
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve

Slideshow: These overlooked Mercedes-Benz models never got the spotlight, but they quietly delivered more than most remember.

By Verdad Gallardo | 2026-04-13 19:35:45


VIEW MORE
story-8
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping

Slideshow: A well-used 1991 Mercedes-Benz 300D with more than one million miles is now looking for a new owner, and it still appears ready for more.

By Verdad Gallardo | 2026-04-10 10:05:15


VIEW MORE
story-9
10 Most Reliable Mercedes-Benz Models You Can Buy Used

Slideshow: From bulletproof sedans to surprisingly tough SUVs, these Mercedes models proved that the three-pointed star can go the distance.

By Verdad Gallardo | 2026-04-08 09:55:49


VIEW MORE