Hi all

I have been fighting problems on my 1998 XJR for some time, I have had an expected air leak on Bank 1 as it is running rich, whilst looking for the leak I have changed all the timing chains and tensioners, they were in a really bad way.

Thankfully when I had done all the work she started up first time, although she still ran a little rough, so I have just run some tests with the OBD II scanner and found the following information:

Fuel Trim Data
Short term fuel trim Bank 1 - 19.53%
Short term fuel trim Bank 2 - 0.00%

Long term fuel trim Bank 1 - 14.84%
Long term fuel trim Bank 2 - 1.56%

Oxygen Sensor Data
Bank 1 Sensor 1 - 0.000v
Bank 2 Sensor 1 - 0.225v

So looking at the above date it looks to me that i have a problem with the Oxygen sensor for bank 1, apart from swapping Bank 1 with Bank 2, is there any tests that i can do before going out and getting a new one, or is there any other courses that would give me the same readings?

Engine hot, parked. Do those figures drop if you rev to about 2500 and watch them? To what sorts of values?

The engine is up to temperature and the car is parked

I did check briefly at the time and the Oxygen Sensor Data Bank 1 Sensor 1 - Does not change, I have removed it and cleaned it with MAF sensor cleaner but no it had not changed the voltage reading

All other values do change, I can go an check again later

It's not super costly to change the sensor - though it may be the wiring etc - if you're (reasonably) sure it's bad. But... you've big LTFTs on both banks which is commonly a fault common to both banks.

The new oxygen sensor arrived today and was fitted tonight, the sensor is now giving a voltage feedback, so all seems good

Bank 1 Sensor 1 running at idol is between 0.400 to 0.600 volts
Bank 2 Sensor 1 running at idol is between 0.400 to 0.700 volts

Short Term Fuel Trim Bank 1 between 0.78% and 3.91% (Lean)
Short Term Fuel Trim Bank 2 between 0.78% and 4.69% (Lean)

Long Term Fuel Trim Bank 1 between 5.47% and 4.69% (Lean)
Long Term Fuel Trim Bank 2 between 9.38% and 7.03% (Lean)

So all seems to be running well from what I can tell

I didn't do a reset, not sure if that makes any difference?

So, it looks to me like yiu have a small air leak or a dirty MAF. Not too bad, but 5.5 to 7 % LTFT is getting on the highish side.

I'll clean the MAF art the weekend, I have sprayed around the air pipes with MAF cleaner to try and find any leaks but nothing showed up, I have recently done a timing change change so thought re-seating everything would show any leaks, oh well, keep looking

It should auto relearn; disconnect battery to speed it up.

Places that hide air leaks on an R:
The part load breather and the full load breather can crack lengthwise and it is very hard to see!
The rubber bushings at the top rear of the intercoolers on the early models can become unsealed at the compression joints
The intake tube resonators can develop hard to see cracks in the plastic at the attachment points
Several folks have reported leaks at the TB mounting flange
I had a weird one where I had damaged the front main oil seal- it was dry because of the vacuum, but was leaking air in
The oil dipstick should have a small viton seal
The valve covers

Remember that the entire engine crankcase is under vacuum from vacuum sources in downstream of the MAF, so any air leak into the crankcase, in addition to manifold leaks can get you.

I gotta tell you- once I started using a smoke machine to search air leaks, I will never go back to the propane/ air hiss/ this cleaner, that cleaner methods again!

Oh, add injector o rings to the list!

I have ordered a new full load breather, Air intake tube. The Valve covers have been resealed with new gaskets and the dipstick seal is good, so that's a few things off the list

When you say smoke machine are we talking about a Fogger, Disco Smoke Machine like "Prosound 800 smoke machine" or is it specific one for automotive?

There is a specific one for automotive. A homebrew can be as simple as a cigar in a tube with some fittings, or a paint can encapsulating a soldering iron stuck in a cup of oily rags. A little pressure then blows the smoke into a tube that yiou pressurize what you want to test.

I bought mine ready made. This is it, but I am pretty sure I paid a lot less:
OTC6522 Leak Tamer - Smoke Machine - Evap Tester