Is it possible carbon build up in exhaust manifold?

 

I can get mine to 98% on an XJR.

 

Thinking further, is the mileage what the computer is recording, or what you are measuring at the pump when you fill up? Just wondering with all the work you have done to the fuel system if you have a leak somewhere? Possibly in-tank, if the small piece of hose has come off the pump pickup? There was photos of that on here a few months ago.

The low performance is one symptom of either reduced fuel flow or low fuel pressure, but you should not get poor mileage to go along with that. An external leak causing low fuel pressure on the other hand would cause that.

 

OK here are some results from the Torque App

My LTFT are at 7 now, the LTFT same as before.

The MAF reads between 1 and 13 cfm roughly

I did see this failure on a test but I can't decode what this really means. A faulty 02 sensor? If so which one? Bank 1 Sensor 2?

 

Is that your LTFT at idle? How does the STFT & LTFT look when driving around? Is it the same on both banks?
I haven't used the torque app before, so I am not too familiar with how it displays data. But you should be able to get readings for fuel trims on both bank 1 and bank 2 and voltage for all 4 O2 sensors. I have found the cheapy $100 harbor freight OBD scanner will give all this info in live mode.

 

More screenshots from Torque

 

Was this at idle? If so, those numbers look suspect. Idle throttle position should be around 12%. Not sure what the 2 AFR gauges show, but one is indicating very lean, the other very rich. The MAF gauge is also showing a volume, not mass. It should be indicating in kg/s not CFM.

 

It was at 40% throttle...

 

in a poor way I guess I'm asking if that was reasonable under the test conditions at the time. If it was at idle, yet showing 40% throttle, which should be incorrect; then we have to dig further.

 

It's not at idle. It's at 40% throttle when I took that screenshiot. I hate this car!!!!

 

Since I clearly don't care if you call me a ******** again, I will re- suggest you take the multiple suggestions that you look into the possibility of a bad MAF sensor!

 

I appreciate your input man. I just thought you were jumping down my throat a bit last time. Water under the bridge. Your insight and opinion are highly respected and appreciated.

Are the aftermarket rebuilt MAFsensors any good? I don't want another used one that can end up in a similar situation...

What about this one?
1997 Jaguar XJ6 Mass Air Flow Meter All Models 49-00298 R

 

Wow! That is a lot of money. Do you know anyone you could borrow one from? How did "your guy" claim he tested yours? I have one here, but I ma not sure it is any good, either.
I read that they had become less available, but I had no idea how much they cost these days!

 

I see them on Ebay UK fairly cheaply, under $100 anyway. Lots around £30.00 plus postage

 

I purchased a new to me, used, MAF from a British parts recycler in Ranchco Cordova, CA. Cleaned thoroughly with MAF cleaner AND....No difference...ARGH

 

I believe it could be the timing advance is an issue. At full throttle I'm getting 19 degrees max. What could cause this?

 

Timing has seemed to me to be the problem for some time. I don't know if the crank damper could cause this or not. Easy to check the damper. Put white marks on all three flanges in line. After the car runs for a while they may move indicating a bad damper. Just another idea.

 

While at my mechanic today, he mentioned that. I will do that.
The fuel trims check out ok on the highway, so perhaps that isn't the underlying issue. I'm so frustrated with this.

 

Most mechanics that I know don't know how to check the crankshaft damper. There are three ranges or rings on the damper. Put a white paint dot on each flange. Drive it. They must stay lined up after you stop. May take some driving. If they don't that could be the problem.

 

Timing will be retarded under full throttle. You'll see maximum advance under light throttle highway cruise conditions.