Ah. Thanks. My mechanic was sure of that, but I of course, stubbornly, was thinking the opposite. Good to know, as I was a little freaked that there was a degradation in performance without throwing the CE light on.

We sure went through the car with a fine toothed comb, and pretty much everything is now renewed. All the suspension looks good, no leaks (other than the valve cover gasket) and no other concerns. I recently changed the oil/filter and cabin dust filter and engine air filter. Brakes are about 40% rear and 60% front, so they'll be fine for some time.

Only things left are to replace the pitted windscreen (next spring) and the cracked headlamp lense. Probably do the lense after the snow goes and the rocks are cleared as well.

Yes, there is some flexibility there, that's the whole reason behind this self-adaptaion, it can adapt to different conditions, and it's expected it will creep one way or another, especially later in the engine life (engine wear). Ideal is 1.00, that's right in the center. But if the mixture starts running too rich or too lean, it has to eventually stop adjusting the mixture and call it quits as far as self-adapting anymore; if it keeps leaning out the mixture, well as anyone can say it won't run well without enough fuel, and of course if it does at least keep running, in a too-lean condition the motor will eventually "melt down". Just the opposite, too rich is no good either, especially for the environment and the cats, and eventually you'll flood the engine. As you can probably guess, the MAF sensor being incorrect can lead to this self-adaption being all wrong. The MAF sensor helps determine the self-adaptation, the front O2 sensors determine the actual Lambda cycling of the mixture (rich-lean-rich-lean), the rear O2 sensors aren't really for anything except determining that the cats are doing their job.

Gilly

Wow, that last post is awesome, and yes, I do know it was from 3 years ago...but nothing like using the search button to find relevant info eh? :pleased:

How do I determine what the current fuel trim is on my vehicle? What is the expected life of an 02 sensor? Especially one that perhaps was cooked by a clogged cat at 110K miles.
Cat was replaced with Magnaflow Cat for $300.
Anyone else using these? Are they OK?

I'm pretty good about staying up on things.
Fuel filter was replaced 30K miles ago,
plugs are recent, all coil packs were replaced around 80K, generally runs good, but a little sputtering, and even an occasional backfire perhaps. Seems to be dumping too much fuel.
MAF (same as a AMM?) was replaced at least twice by the dealer under warranty, and
I cleaned it just a few months ago.

Could just the 02 sensor be causing this?

I just called a parts store I've dealt with a lot in the past. They have a Bosch universal 02 sensor for around $80, you have to solder the connector.
He swears it's the same as the original, just without the connector.
I know from experience that 02 sensors do tend to be the same, and bosch is the main supplier and designer, and each car mfg tends to jack the prices up.

Anyone try a universal before?