long term fuel trims, what are yours
 

I've been looking at my fuel trims while fixing the bank 1 lower O2 sensor.


At idle mine are;


Bank1 ~6%
Bank2 ~0%


However I have no idea if this is typical, due to normal wear and tear, a failing O2 sensor, weak injector or vacuum leak, so thought it would be good to compare to a few other cars.

just checked mine and shows LTFT1 @ 14.1 and LTFT2 @ 14.4 with both Bank 1/2 STFT's @ 8.6 - not sure what they should be as just started using the Torque Pro app about a month ago.

Found this previous thread on fuel trims with some good info - specifically should take when engine is warm - took mine when not quite at operating temps. I have a few errands to run later so will take a second set and post

https://www.jaguarforums.com/forum/x...-trims-109508/

-17 :(

Should be interesting to compare.
It would probably good to have numbers at idle and around 2500 rpm to compare.

took the car out for a ride and checked again after I got home

At idle LTFT1 @14.1; LTFT2 @ 14.8 and both Bank 1/2 STFT @ 0.8.

At 2500 RPM, LTFT1 @5.5; LTFT2 @4.7; STFT1 @ 14.1 and STFT2 @ 14.7

My last test in park was LTFT1=3.1 & LTFT2=7.8 and at 2500 RPM LTFT1=3.1 & LTFT2=3.9. You may want to compare your trims with the attached chart but before doing this do a hard reset and drive the car for about 20 to 30 mi. At the end of that drive do your test and record your results then do it again at around 50 mi. and see what you come up with. Note do your test outside in an open area. When you do it for the first time you will understand why!

Link JagRepair.com - Jaguar Repair Information Resource

LTFTs about the same and reduce also about the same: classic sign of an air leak. Can't be very big as no codes and LTFT only 14-ish. I'd go hunting for it but up to you.

JagV8 - appreciate the feedback - after reading the guidance from Gus's site I was wondering if I should be concerned - will take a look as no codes right now

They're not bad enough to panic. (But I'd still go looking.)

I'm planning on building a cigar powered smoke machine over the next few days, Ill post up the pictures.

I AM a cigar-powered smoking machine!!! :icon_beerchug::icon_pimp::icon_hyper:

I have been looking at making one for myself so I am interested in seeing what you come up with.

I gathered together some odds and ends.


https://www.jaguarforums.com/forum/a...ine=1391463541


This container has two sealable lids but it is not critical, I used heat glue (faster than epoxy which would be better) to fit the tubes to the two lids and a cigarette was pushed into the tube.


One end goes to a pump used to blow up camp beds powered from the cars 12 volt outlet and the other goes to a tin can which had a bicycle tyre valve glued into it, I drilled out the valve from the body.


https://www.jaguarforums.com/forum/a...ine=1391463541


https://www.jaguarforums.com/forum/a...ine=1391463541


I butchered an old battery powered drill to make a "day light" torch for paintwork inspection and this will be handy to use to identify any pufs of smoke. The halogen lamp I used is 12 volt but goes super bright at 18volts.


https://www.jaguarforums.com/forum/a...ine=1391463541


This is the camp bed pump I used, however it is too powerful as it burned out the cigarette in about 10 seconds, I will rig it up to a lower voltage power supply so it lasts a bit longer.


https://www.jaguarforums.com/forum/a...ine=1391463541

I've not tried the smoke machine yet, I'll do that at the weekend, but had another look at the fuel trims. Something I did notice was that the lights and A/C made a noticeable difference to the MAF, so for anyone doing some comparative testing it is best to ensure these are off.


After a 20min drive, in Park, ~ 650rmp, MAF = 4.36g/s, LTFT1 1.56, LTFT2 -1.56 but the trims drifted over the next 5 mins up to LTFT1 7.8, LTFT2 4.48 and then stayed there.


Moving into Drive only changed the RPM down to 600 and the MAF up to 4.73g/s, not too surprising as the engine was now slightly loaded.


At 2500rpm in Park the MAF went to 13.5g/s, LTFT1 8.56, LTFT2 6.24.

hi
that's my thread referenced early on, thought I'd add to the end of this section as well. I think I have a problem with bank 1:

IDLE:

Mass air flow rate 4.75

ST Bank 1: 5.4
ST bank 2: 0.78

LT Bank 1: 19.53
LT Bank 2: 7.82

2K revs:

MAF rate 16.35
ST bank 1: 12.5
ST bank 2: 2.34

LT bank 1: 13.2
LT bank 2: 12.5

From what I've read, LT trims under 10% are pretty normal. Around 20% is not! I'm interested to see how this smoke machine turns out.
I have an 02 sensor about to go in; will be a week or two before I can test it as I've got the car up on jack stands for some body work. Good luck with your leak hunt!

Be sure to look around the intake manifold. I ended up having a cracked intake manifold and I have heard of a few others with the same problem.

Those are all quite high LTFTs so maybe more than one problem. Try for an air leak first I think and see what you find.

I tried the smoke machine today.


The tin can fitted in the end of the intake tube perfectly, must have been the same diameter as the TT


http://racediagnostics.com/cms/uploa...oke%20%206.jpg


On to try it out.




Looks like I should have put on a new gasket when I had the TB off to repair the heater pump!

What a great machine! Thank you!