104.992 Partial Load, loss of power at OT - PeachParts Mercedes-Benz Forum

oldtrucker · #1 05-03-2014, 06:56 PM

This has been bugging me for a while.

The car runs fine until it reaches OT (Operating Temperature).
Not really true, the idle when below OT, is a little rough but gets better as temp increases.

At OT it loses power under partial load.
I have taken out the switch over valve and ran it on the bench.
Although, it doesn't sound as good as the EGR valve, it still closes the vacuum path.
On the other hand, the pump is off, via clutch, at OT anyway. I am thinking that the shut off valve or the air check valve may not work properly.
Is there anyone that may have heard of something with the described symptom and either valve involved in it?

I checked the vacuum and read a decent number, haven't gotten around to check when at OT, since it should be off, I think.

On a second note, I get Throttle body Flap position value too high.
This would lead me to think that the used one I bought has a defective flap position sensor e.g. potentiometer that may lift off at OT (when hot expands slightly) and mid to low range position (most stressed in city traffic), causing the power loss.
Anyone heard of something like that?

Any input is appreciated...

oldtrucker · #2 05-23-2014, 07:44 PM

Just a follow up....

Many times I see post's that end up in nowhere. There is no conclusion. I understand that sometimes people are happy to have their problem fixed and go on with their life's, but I think it is also nice to see the conclusion of a problem and what fixed it.

It seems that my problem was related to multiple sources.

1. Checked for vacuum leaks, (this is the most difficult one) found a rubber coupler leaking, replaced it with a new one on.
2. Checked fuel pressure. Was good. I had replaced the Fuel Pressure Regulator just 3 weeks ago!
3. Checked the Purge Valve. Was at first stuck open, then after the WD40 treatment, was stuck closed (engine ran already better). Had to replace it with one from the junk yard. Works now.
4. Starter Motor burned up. Replaced the starter motor, although unrelated to this post.
5. Checked the EGR pipe. Was blocked! Cleaned that one out. MIL went almost instantly off. Engine has power in the mid to high load range. Idle is still a little tiny bit rough.
6. Reset the ECU to mean values.

I am confident that it will now run as it should.
Arthur Dalton, was a great help in troubleshooting, many thanks to him.

Cheers

liquiddog · #3 05-23-2014, 08:33 PM

Thanks for posting this. I need to check my switchover valves at the egr vacuum lines.

My first ever post was answered by Arthur Dalton in a PM after the trolls already dropped troll bombs on me. We need to make some sort of Arthur Dalton shrine. I'm thinking something along the lines of a Buddha statue and waterfall. Maybe with one ounce gold coins glistening in the bottom of the pool.