Well this seems to have shown up with the cooler weather - as in 50-60f outside instead of >80f
it's very transient in that it has produce the code twice and says reduced performance yet
that goes out very quickly - cleared the pair of codes and will see - wonder if injector(s) issue

 

Had my code reader with me just in case - had the close to 10yo tires replaced today - road test -
kicked it up to 90mph for a bit runs great - new tires are a wonderful thing as well - no codes - so
wait and see

 

Check the live data and see what your long and short term fuel trims are. You probably have at least one of them very close to the maximum which is occasionally going so far the car can no longer correct for it, hence the code. Usually an air leak is responsible, but post the values here for more informed guesses.

 

I had a very similar experience. I smoke tested and found leak in the plastic air duct. Fixed that and replaced throttle body gasket. Everything seemed fine for a few days. Then codes appeared again. The real problem was MAF sensor. It tested fine on my scanner but changing it solved the problem. Apparently some of these MAF are better than others. I used a Denso and have had no problems;

 

Quick snap shot

 

That shows around 20% extra fuel on both banks (slightly worse on Bank 1), so presumably in some conditions it hits 25% and the car can't add any more fuel hence the lean condition.

Try cleaning the MAF and look for an air leak.

BTW You have an extra space between the ".jp" and the "g"

 

Thank you - i'll clean it this afternoon and re-scan

 

use MAF cleaner and note that the flow sensor is inside the tube. The external sensor is intake air temp.

 

ok after a maf cleaning and all air flow paths checked for leaks nothing found - it is 10-15f warmer
than when the last test was ran - this is right after a rather sprited drive she's run great

 

one question about the '98 xk8 maf - when I had it off spray cleaning it sure would
have been easier if the sensor itself was removeable from the housing - it wasn't
obvious how to do so - later models and other maf's i've worked with just have a
couple of screws hold the sensor in place - this '98 seems to be one piece is
that correct?

 

On my 2001 AJ27S engine the MAF is separate from the intake tube - two screws hold it in place. I know the earlier cars were one piece, which it sounds like what you have.

What scan tool are you using? The way it has labelled those trim values isn't correct, which makes me wonder what else is incorrect on the live data. A cheap OBD dongle and the Torque app gives better information than that - it's hard to get a good picture of what is happening from your print out, but it looks like the O2 sensors have changed values a lot as well as the trims (or is that just because of the snapshot?).

 

it's a autel maxiap ap200 bluetooth dongle - after some further reading here I did the
test held it steady at 2000rpm watching live data and all the trims went to > 5%
back to idle and the 2 "upstream" (long term i assume) move 17 to 18% saying
I have a vacuum leak - looked and felt over the plastic accord pipe best I could
but a crack maybe hiding in the ridges - think about a Mina aluminum replacement
with heat shielding.

 

That could certainly explain it - as the intake pipe flexes cracks open and close.

Let us know how you get on.

 

During the install of the Mina intake pipe it sure seems to me the factory rubber gasket at the throttle body
sure wasn't a tight fit - enough to cause a mild air leak do not know - but so far so good with new intake pipe
but we have had a considerable warm up - had to switch from heat to a/c in the house normal Houston weather