no power at full throttle

99 E240 60K: Recently the cars performance has decreased drastically. It goes better at part throttle than at full throttle! I tested it today. If i floor it and it
kicks down into second the engine stops to pull and refuses to go past 5.5K and it doesnt upshift. This was on perfectly flat road with only me inside. I also tried it in 3rd and same thing happens. Above 5k it hits a wall and refuses to go faster than 5.4-5.5K, and i doesn't upshift until you let go of the gas. The engine doesn't seem to struggle, but it just does'nt want to go faster. At about halv throttle it's seems there a "sweet spot" and if i keep the pedal there it will pull smoothly to 6.3K before upshifthing. But when it upshifts it "takes a break" for 0.5 seconds before the next gear goes in with a bang and push in the back. Clearly something is not right. I'm thinking some electronic stuff that manages engine/transmission, or a transmission that is about to blow?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
First look at the simple and cheap things, the complicated and expensive things can wait.
When was the fuel filter changed? If too long ago, replace it
Can you get any fault codes from the engine?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sounds like a vacuum leak, particularly concerning the upshifting when you "let go of the gas" which is when the manifold vacuum is probably at its highest. I know next to nothing about this car, but I would look for a vacuum line somewhere that has become brittle or otherwise unservicable.
I second the notion of changing the fuel filter. A loss of power at speed is the first symptom. Depending on the capacity of the filter, the engine will eventually refuse to run at all.
Regards,
Ken

it
5.5K
inside.
to
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My 98 e320 w/ 65,000 was behaving the same way.
A new Mass Air Flow meter and, for good measure, new 02 sensors has it roaring like a tiger.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.