Date registered: Jul 2006
Vehicle: 1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
Location: NW Arkansas, La Jolla CA, Hong Kong
Mentioned: 6 Post(s)
Quoted: 157 Post(s)
Sometimes advice can be misleading..
Running "open loop" is not the solution to "performance" - and will just lead to premature failure of the cat's.
The O2 sensors have way-way less importance (if they are not throwing codes) than a MAF. The tolerance on the MAF can go way off, before throwing a code, and that variance can affect "performance" way-way more than a O2 sensor that has wandered from spec (again, that has not yet thrown a O2 sensor code).
1) Do a forum search - a proper "hard reset" WITH KEY OUT OF IGNITION disconnect both battery cables from the battery - touch trhe ends of the cables together, I twist tie them together for like 1 min, then reconnect the cables to the battery, and then WAIT for about 10 minuted BEFORE you put the key back in the ignition.
If you disconnect the battery for 2 minutes, without lopping out the system with the cable end connect, then the ONLY thing you are doing over a "soft reset" is killing the accessory system codes (like radio, windows, etc).
Make sure you follow ALL the system reset procedures outlined in the actual owner's manual.
2) If you easily want to maximize your existing perfomance - do a "soft reset" - which resets the major systems, but does not zero out the acceossry systems. After the soft reset, no additional reprogramming of accessory systems is required.
If the car has been not reset in 2-3 weeks, then if a "softie" doesn't immediately perk up the zoom-zoom, then start looking for other symptoms.
I have seen more (a) no softie reset (b) aged/out of spec MAF, and (c) dirty air filters do more to screw up E55 "performance" way-way-way more than failure of specific mechanical components.
If you are not happy, then the cars is worth the chase.