PeachParts Mercedes-Benz Forum - View Single Post

rcounts · #14 05-22-2008, 05:12 AM

Quote:

Originally Posted by pmckechnie

Biglex, There is a lot of good information on this site but sometimes you have to sort the good from the bad.
For instance, on the 602 engine in the 90 to 93 300D is different from the 617/603 engines. It is basically the same but the control system is quite different. First, if you disable the EGR system the car will run really slow. The computer will detect the EGR is not working and will disable the turbo. The EGR can be removed but the turbo system has to be changed to a non-computer type by changing the waste-gate actuator on the turbo. Now for the ALDA, I tried removing mine and the black smoke was a hazzard to anyone behind me and my mileage was terrible. I reinstalled it and adjusted it out about 2 turns (CCW). It runs great now, gets 32 MPG on the road and 24 driving about 3 miles a day. I also found that using 10W40 fully syn oil made a big difference in power. The turbo will spool up much quicker. It starts making boost by 1500 RPM and is at 14 lbs by 2200/2300 RPM. Also, the air pipe that goes from the turbo to the intake manifold has a tendency to plug up from the blowby gases mixing with the EGR exhaust. It is not difficult to remove it and clean it out. Also check the vacuum lines from the intake manifold through the overboost valve to the ALDA and make sure it is open. These are really great cars, run very well for the engine size and car weigtht, and will last forever if taken care of.
Enjoy
Paul

Good info on the EGR and the computer controlled turbos. I didn't know that was the case with a 92. Thanks for (sort of) correcting me on that. I'm here to learn and just so I don't make that mistake again, what year was the computer control introduced?

On the issue of the ALDA adjustment, what I do know for sure is that it was the first suggestion in another thread I started on another MB board. I followed the directions I was given and adjusted it a half turn at a time 'til I saw black smoke on WOT launch from sitting still and then turned it back in about a quarter turn. The result was lots more power with no black smoke from off-idle. Seems to have solved the problem.

As for the other items you suggested FI, I have to admit to not having checked the valves (no noises though) or chain stetch, but all the others have been and were done first. Linkages are all tight, and the filters were all new except the air filter - which I replaced before the ALDA adjustment. It was still sluggish until the turbo spooled up and then a BIG surge in power. A little tweaking of the ALDA and that problem seems to have been solved. Now I have smooth acceleration as I apply the pedal from off-idle - with power building very linearly until the turbo builds boost (around 2k RPMs), and then just a mild "bump" in power when it spools up and boost kicks in, followed by an even greater, but still linear, power increase as I apply more pedal.

A valve adjustment and timing check are next on my list, and I guess it only makes sense to check the timing chain too - while the valve cover is off. That will be followed by a Diesel Purge to clean the injectors up.

My only question is IF adjusting my ALDA has in effect "masked" one or more of those other problems as the true culprit for the off-idle sluggishness I was experiencing, what can I expect once these other things are done? Excessive black smoke until I adjust the ALDA back in?