Hello!

I´m the owner of a 190D 2.5 Turbo -92 (VIN 2011281F965640) with an annoying problem. When starting the engine (engine cold) everything works normally. When reaching normal operating temperature, i suddenly
looses power. First I expected some diesel line trouble, but since I didn´t find anything unexpected I turned to the turbo system. Installed a Turbo pressure meter and did some test driving. It turns out that
the turbo pressure disappears after a while, typically 1-5 minutes after starting the engine.

I´ve done some investigations on this. First checked all vaccum lines.. Seems to be OK. Next turned to the electrical parts. Realized that the car is equipped with an EDS box. Got an analog multimeter and hooked it
onto the X11-connection to be able to retreive fault codes. Got a numer of error codes (15, 5, 4, 8, 2, 3), cleared them all out (since the clearout haven´t been done for years I guess), and took the car for another
testrun. When loosing turbo pressure again i returned to the multimeter to check error codes. Only number 5 appeared this time. (Number 5 indicates failure in the EGR system).

I've got an error troubleshooting diagram, where I´ve checked all components according to fault code 5. Everything seems OK.. Ordered a new vaccum transducer, which I got yesterday, but changing it didn´t make any difference.

Here is my questions:
- Under what circumstances do the EDS set error code 5?
- How do the EDS realize that there is a fault in the circuit?

Any help is greatly appreciated!

This is a link from the MBCA club website where several members were trying to solve a boost related problem in a W124 OM602.962 car. Assuming your boost control system is the similiar take a look at post #4 in the following link.

http://mbca.cartama.net/showthread.php?p=57707#post57707

According to Jtripp over on the MBCA site the EDS computer looks for a reduction in engine airflow during EGR operations. The reduction in airflow is expected since EGR operation introduces a small amount of gas from the exhaust system. If the specified reduction in airflow is not "seen" a EGR fault is assumed.

Have you checked the vacuum source to the EGR transducer and the vacuum supplied to the EGR valve? As I recall EGR functions are also temperature and RPM related so faulty sensors in either of these areas could cause problems.

Thanks for the reply!

I figured out, that it had to be one of tho reasons to the fault code.

1. The EGR had to be malfunctioning.
2. The Airflow sensor had to be malfunctioning.

I decided to start with the EGR system, removed the pipe and the EGR itself and cleaned them. When examining the bypass passage between EGR and the vaccum pressure housing (the section between the turbo and the intake manifold, with the vaccum controlled flap), I found out that it was completely full of a soot and oil mixture. I removed all the dirt and reassembled the EGR system. Now, when driving, no error code appears and the turbo systems seem to operate.

BUT...

I still have some problem with the charging pressure. When hitting the pedal, I get a pressure up to 0.5 bar. It keeps holding that pressure through 2:nd gear (maby dropping 0.1 bar or so), but when engine drops rpm due to 3:rd gear, pressure slowly falls to 0.1 bar even though the engine rpm keeps rising.

This problem seems to be present after cleaning the EGR system. When I had the EGR full of dirt, i got pressure up to 0.95 bar, and everything seemed to work normally. (Well, except that the EDS after a while decided to cut everything out and leaving me with absolutely NO pressure.. )

Any ideas?

See if this helps 2.5 Turbo Boost problem.

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