I have something to say here... (archive)

First of all, a faulty chain tensioner can cause detonation because the faulty tensioner can cause the timing of the motor to change. Since the spark is timed off of the cam, what could have happened, and most likely happened, is that with no or little tension on the chain, the timing will advance. If the individual is not running premium, it will detonate like running a performance chip. If they had voided the warranty because of this someone did not understand what had happened with this failure.
Now onto the DME problem. I hate to inform, but I have worked with motronics now for a long time, over a decade. The simple fact is, the motronic will never under any situation lean out the motor. The fact is that the motronic is programmed to make the motor run rich if there is a fault. Now I agree that the car should be looked at by a qualified BMW tech, but the simple fact is that it is very possible that the motor is not running right because it is running too rich. If this is the case, the DME is most likely not bad, and a sensor or component of the injection system is. While it could be the O2 sensor which is the owners responsibilty, on an 8.0:1 compression ratio motor, it is very easy to get it to run properly. If you are having problems, it is most likely NOT your engine management, but a sensor or possibly something internal. (DME's do go bad but, it is not a very often occurance in fact it is extrememly rare) DME's in these cars do not run after they die like in later BMWs causing driveablity problem and also possible engine damage. When a DME goes bad, the car won't run, period. If the car runs it is not the DME, it is something else because the DME does not fire each individual injector and it controls very few other functions.
My advice to the individual with the motor is to take it to a qualified tech and have them compression and leak down test it and also test the exhaust gas emissions. This will provide the exact reasons for the problems.

Rob
M535i SIG Chief Technical Advisor
www.m535i.org

I wrote a letter to Bavarian Engine Exchange quetioning what supposedly happened with this guy. Well, it seems the whole story was not told!!!!

EVERYONE PLEASE READ THIS.You who posted should feel embarassed as hell:

"James: Thanks for the feedback.

This customer did have a legitimate warranty issue (bad timing chain
tensioner) which we found during the warranty inspection process at our
plant. However, we also found serious evidence of detonation (melted heat
tab on cyl head & pitted pistons) caused by a faulty engine management
system.

Under the terms of our warranty (clearly stated on our web sites), these
discoveries would normally void his warranty. But since we did find a
faulty chain tensioner during the inspection, we provided the replacement
as a customer service gesture. The replacement was dynamically tested for
compression, leakdown, and oil leaks before it left our plant.

Now he's having trouble getting the engine to run properly (likely something
to do with the engine management system) and is blaming/flaming us before a
complete and thorough diagnosis is performed by an authorized BMW tech.
Also, I just recently saw a board message from this individual looking to
buy or borrow a DME (injection brain) for his car - imagine that.

The web is a 2 edged sword. It sure would be nice if people would realize
that the long block is just one component of a properly operating complex
engine system - and take responsibility for making sure all systems are good
before attempting to slander a reputable, caring company. At least our many
satisfied customers know how we operate. We aren't perfect (1.3% warranty
ratio) - but when we make a mistake we fix it.

Although we aren't happy with the progression of this situation, we will
continue to do our best to get this guy back on the road (within reason).

Thanks again, Bryce"

http://www.m535i.org

Follow Ups:

[ Follow Ups ] [ M5 (E28) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.