Om 603.971 full throttle question.
 

Hello everyone,I have one question.
I have a w140 with OM603.971 engine,and the car drives nice,it accelerates nice and i drove it 175 km/h.But there is a strange thing if I drive it pressing gas pedal only half way down it goes O.K. But if i press it all the way down (not kick down just all the way down but don't activate kick down switch) nothing happens,it accelerates but much worse than when I press pedal only half way.
I have unplugged the MAF and blocked EGR valve,and the car is way better after I did that but still has a full throttle problem.
Did some one had similar problem or has a solution for it.It is not a big problem and once i got use to it i drive it without a problem but I would like to fix it if I can.
Thank you in advance.:)

I forgot to tell that I checked the timing and the chain stretch and all is O.K.

That car uses the EDS computer to control boost. If the MAF or EGR are unplugged it won't command the wastegate to close, and you won't make any boost.

-J

Yes it does have EDS but i have boost,and it is controlled by boost pressure sensor that tells EDS when to open wastegate.
MAf only serves so that EDS knows when to open and when to close EGR.And since I blocked EGR i have no need for MAF any more.
I decided to put a pressure controlled wastegate,so I wont need EDS no more,except for idle regulation.

Yes I have EDS,but I also have boost,because it is controlled by a boost pressure sensor that tells EDS when to open wastegate.
MAF only tells EDS when to open or when to close EGR,and since I have blocked EGR I have no need for MAF anymore.
I have decided to change wastegate from vacuum operated to boost operated,and then I have no need for EDS except for idle stabilizing.

Are you sure you have boost? Like I said on USA models if the EDS system sees any problem at all it puts the car in limp mode.

Double check that all of the vacuum lines and switchover valves from the intake manifold to the ALDA on the injection pump are clear. They can plug with soot and block pressure getting to the ALDA.

It might also be worth getting a helper to push the go pedal while you watch all the throttle linkages. Until I did that I didn't know that my car was only getting to about 80% throttle on the injection pump!

-J

You can get a cheap boost/vacuum gauge at Harbor Freight and hook it up to know for sure. Very helpful for troubleshooting.

I am sure i have boost,I checked.It is not a problem with the performance of the car.It accelerates good and i driven it 175 km/h.Only problem i have is that from the half to full gas pedal there is no difference,and some times maybe is even worse on full pressed pedal compared to half pushed pedal.
I tried reconnecting MAF today and the car definitely goes better with it unplugged.I measured resistance to check if the readings of the MAF is O.K. and they are.Also checked all the vacuums and lines to check if they are plugged,but it is all fine.Maybe i should borrow someones MAF just to double check.
Also checked throttle linkage and no play,or something weird.
Anyway I want to thank you guys for trying to help me out.
If you have anything that comes to your mind,that I should check,don't be shy to tell.:)
If I find something was wrong I will post.

Are you sure the EGR valve isn't leaking? Does the car smoke more as you give it more go pedal?

-J

It has a little smoke with higher revs,but compressor side of the turbocharger is leaking some oil and it goes to manifold.More boost=more oil=more smoke :).And I am pretty sure that there is no leak In EGR because it is sealed pretty good on both sides.

Is there a flap between the turbo outlet and intake manifold?

Are the fuel filters and tank strainer clean?

Sixto
87 300D

I am sorry but I do not know what FLAP are you referring to?:(Could you explain it a little better?:)
I cleaned the strainer,and changed filters.

This thing between turbo and intake manifold -

http://i.imgur.com/1NzhTpSh.jpg

Which has this flap inside -

http://i.imgur.com/b88whCBh.jpg

If you have such a flap, disabling EGR will cause EDS to close the flap restricting air to the engine even with boost.

* picture credit to forum member JamesDean

Sixto
87 300D

That's interesting. I'm guessing that's a .971 only feature?

-J

My 1992 300D has same thing on intake.