OK, I'm stupid and curious. My 2000 XKR starts and runs great, no engine light and no problems. BUT I'm using a ODB reader and the Carscanner app on my phone to monitor mainly water temp and voltage.
Unfortunately I have monitored the AFR, STFT and LTFT (Air/Fuel ratio, Short term fuel trim and Long term fuel trim)
Last couple of days I have driven at 50 mph with the cruise control on and suddenly the AFR are 11 on both banks and the STFT is -25 ? OK maybe my AFM are bad - but wait after a while the AFR at bank 1 is 14,6, but still 11-12 at bank 2 ??
If I use the throttle and drive at higher RPM it often get better and both banks become normal. So maybe the fuel pressure regulator are faulty or missing vacuum? But why not both banks all the time?
The LFTF are constantly changing, is this normal? I thought Long Term was longer than a few seconds?
Any thoughts? Anyone else that has monitored the AFR and Fuel trims and can tell me whats normal?

 

What are LTFT at idle after driving for 1/2 hr or so?

 

Seems to be a classic case of information that doesn’t point you in any actionable direction.

You don’t have any codes. The car is running fine. Just stop right there and drive the car without looking for trouble where there likely isn’t any

Free advice worth exactly what it cost you .

Z

 

OK,
one question; using cruise control what is your instant mpg going about 60 mph for 5-10-15 minutes . The dash info that the turn signal stalk button operates should reveal that. If it’s in the 20-25-28 mpg for “instant fuel mpg” reading then I say you don’t have a problem.

or you can hit the zero out button on the dash once you get going at the right speed and then use the “average mpg” reading after driving for a few minutes to let the system take the average instead of an “instant snapshot” . The average is probably more meaningful.

Again, if your mpg is in the mid 20’s then your car is operating as designed.

just my 2 cents

 

Just a few observations. The long term trims are in fact a table of values for different RPM and engine loads, so they will change as those factors change. The short terms are instant. You need to add the two together to get the current value - what are your short term plus long term trims looking like?

Also what are your lambda readings showing?

You might be getting close to the limit, but I don't really understand the AFR numbers - if those are real you would have a code.

 

This is common on these cars clean the mass air flow sensor and usually the connection needs a bit of snuggling up I posted the same thing on mine use the mass air flow sensor cleaned check the wires to the plug plug and unplug a couple of times these cars are very sensitive to the connection. Mine fell right into range and what a difference on the gas mileage

 

Good advice, I know. But my brain want forget it now that I know something I dont understand. And IF these numbers are correct it would not be good for fuel economy, and if you think 4$ per gallon is expensive - try live in Norway! And yes you dont drive these cars if you want low consumption, but if I can drive it as today with the same power and use less - thats good in my book.

 

Running at a constant-25 will eventually trigger a bank 1 and or 2 lean code it takes a few trips to trigger it if it is going to trigger

 

that's why I follow up wanting to know what your gas mileage is.

cleaning the MAF sensor (which is the wire deep up in the sensor unit, not the exposed bulb at the bottom) with a dedicated cleaner like CRC MAF cleaner is always a good idea, So is spraying the electrical contacts that plug into the MAF assembly with an electrical spray cleaner.

As noted, many have improved their fuel trim numbers just by cleaning the wiring connections.

Z