Dear Forum,

My bank I is very well behaved; a few percent (either way) long keeps short at zero.

However, is it okay that my bank 2 has to go (at idle) mostly minus 4-6 % (it varies) sometimes all the way out to - 10 % to keep my short term bank 2 near the zero? I do not get why bank 2 needs to remove so much fuel? I mean, if there was a vacuum leak on bank 2, I would understand the ECM adding fuel to burn it, but what condition would cause the ECM to reduce the fuel so strongly on just one bank?

Unless of course I have completely misunderstood this whole subject?

Everything seems to be running beautifully (especially now I have replaced a failed thermostat)….I mean, please do not misunderstand me, for a normally aspirated V8 this thing really GOES!….Please, should I just calm down and leave it alone?

 

Is this with a hot engine, parked?

And is it at idle or when revved (about 2500rpm)?

It doesn't sound like an air leak but maybe just post the LTFTs at idle & when revved to allow some thoughts.

 

Hot engine parked

At idle.

I will post LTFTs at 2,500 revs

 

Hello JagV8,

Thanks for your help:


At Idle

2500 revs

 

Looks good enough to me.

If it flags "lean" codes, see what the freeze frame says - but it doesn't look likely to flag any.

 

Hello JagV8; thank you as always, You know, what puzzles me is that my ECM seems (to me) to be constantly taking fuel away (particularly on bank 2)...Unless (despite reading the attached very informative Fuel Trim Primer) I completely misunderstand what the minus LTFT trims mean (certainly not unlikely)? Would it not add fuel (plus readings) if there was an air leak that required more fuel to burn the excess oxygen? So why would it flag 'lean codes'? My problem appears (to me) to be running too rich and the O2 sensors are saying, whoooar there!

Or have I got this completely wrong?

Best regards, Ray

 

IF I UNDERSTAND, what the system is trying to do, is to match both long to short as close as possible to each other, with zero as the ultimate goal for both.
Squeeze every bit of power from what is burned so nothing is left.
They have it down pretty darn close when all the oxygen is burned, impressive.

 

Currently, it is indeed reducing fuel. Whether it was doing that in the past I don't know, but it wasn't - at the very instant - if it flagged a lean code.

You'd want the freeze frame data to see that instant's conditions.

You may well now be looking at very different conditions (speed/load/rpm/...).

 

There are no codes. Bank 2 has always been reducing fuel at a higher rate than Bank 1. However, that rate has recently increased from around 5-6 % to 9 -10%? The only work have I conducted recently has been to replace number 7 Fuel Injector and replace the Thermostat? If I have a vacuum leak in the air-box to TB inlet pipes, I should expect fuel to be added, wouldn't I?
Fuel being added to burn unmetered air is easy to sort...Find the vacuum leak. But please, where do you look to see why fuel is being injected and then removed at such a high rate, on one Bank alone?
Unless or perhaps a Fuel Injector is now on its way out in Bank 2....I will try adding an Injector Cleaner....See if anything changes?
Looks like I will just have to wait until whatever it is gets bad enough to flag a code and some freeze frame data?

 

It's not likely to be an air leak (it would have to be covered up by an even worse fuel problem, and two such faults are staggeringly unlikely here).

Too much fuel can be such as dirty/bad MAF, bad injector, even a part-blocked cat.

 

Thanks JagV8, I'll try some BG Injector Cleaner; not put any in for about a year?

 

It's worth a try. Various techs are keen on BG44K.

 

Thanks JagV8; took what you said onboard. Cleaned MAF with my pukka cleaner; Any MAF problems gonna affect both banks, not just Bank 2. Could be part-blocked Cat...Had somewhat higher Bank 2 negatives since bought car.....Think the Injector (number 7) I recently had to replace could have come from Bank 2 (the garage who cleaned and tested them 'juggled' them, so don't know if the 'problem' number 4 injector I had cleaned, ended up at number 7)?

Anyways, it seems to me that Injector(s) in Bank 2 are my most likely culprit! Do not want to afford to replace them all!!

So, I will try some BG44K and then wait until I eventually get a misfire!

Thanks again for your help....

 

You may not get a misfire. Currently it's adjusting OK.

 

When i dose a vehicle, always double the advised amount.

The Jaguars get two bottles in a full tank of fuel, with a new fuel filter.

 

JagV8, Wingrider,

Might be worth me mentioning that the BG44K has (so far) reduced the bank 2 LTFT back to around minus 6%.

Maybe this is my car's way of telling me that I have already replaced Injector 7 and that the others are tired?