I hate to be the one to bring an old thread back to life, but I am having the exact same problem as DiscoIIBrandon. I read this thread and was also wondering what, if anything, solved the problem. I tried to pm DiscoIIBrandon a couple of weeks ago with no response yet. He doesn't show any activity in the last month or so. My problem is the same except for the Bank 2 Sensor 1 is the problem. Any and all brands work right out of the box then slowly crap out. Thinking ECU, but I don't know. Don't know how or where to get ECU reflashed. Any help would be great. Thanks in advance.

 

Bosch+4plugs, never liked those plugs. If it were me I would drop in a set of cheap champion plugs.

 

OK, a lot of good information in this thread, but also a lot of bad information.

More than likely your O2's are not lazy, the reason they are responding in that manner is an effect, not a cause. The way the system works is that a narrow band is really like a pair of on/off switches, the ecm drives the a/f ratio lean until it reaches bottom limit, then reverses direction and drives it to top limit, then repeats. Normally the system can do this relatively quickly and consistently, because it has some built in tools to help - namely short term fuel trims and long term fuel trims. These act sort of like an offset or bias to the normal tune, helping it adjust to changes in operating conditions (altitude, plugged filter, leaking injector, etc). However there are limits to both STFT and LTFT. Most good scanners will log 02 readings, STFT, and LTFT. The 02 readings should average 450mv, and ideally the STFT and LTFT would be 0 (they are typically either a small negative or positive number).

The reason your system is reacting lazily is there is a consistent bias (sounds like it is rich - most likely from a leaking injector) - if this is true the O2's will average to the rich side and the STFT and LTFT will also go to the rich side and stay there. The biased LTFT can also act like a weight on the control system causing it to react more slowly, which is why the O2's react slowly.

If you can get access to a scanner that logs the readings, post them up, we'll have a look. If it is rich it is likely a leaking injector, if it is lean it is likely plugged injector.

BTW, stock programming is always richer than optimum for power and economy as programmed from the factory - their program is optimum for emissions and warranty. They typically program about 11 to 1 in PE mode (WOT) when 12.5-13 is optimum and 14.7 at all other times when the engine runs most fuel efficiently at about 16-16.5 to 1. If there was an easy way to lean out the mixture on the Rover I would do mine - part of the appeal of the GM ECM conversion...

 

I think he said the aftermarket o2 sensors didn't talk properly to the ecu, so therefore he ordered two oem sensors and has no issues i'm guessing and has left the chat, nothing to resolve anymore.

 

You're getting better...this one's only 3 and a half years old since last post...lol.