Hi all, im a newbie here...have a 1999 3.0 l V6 auto that was inherited from a family member. Car starts well, idles smooth but as soon as it goes into ' closed loop' it starts to missfire, seems to be on one bank only, and you can smell strong exhaust fumes at the back. While driving above idling speed engine is quite smooth (88000 miles on clock) but upon acceleration it misses badly and the MIL light flashes, take your foot of and it stops!! Car needs to go for MOT but will fail on this. Ran a scan using ScanxlPro, snows no codes, either current or stored, but did notice when i hooked it up and went for a drive that the LTFT at startup ( cold) was -2% on both banks...as i drove along this was the average with an engine temp of 91c..varied slightly as far as -4% on both banks, temp stable at 101c, with a speed range of 23-63 KM/h, total distance was approximately 1,4 miles. Slowed down to 23 Km/h, still have LTFT of -2 on both banks, came to a stop in driveway, and idled around 2 minutes and LTFT went to -2% on bank 1 and 13% on bank 2, then switched off. Seems car is overfuelling at idles when in closed loop, seems normal while driving, apart from misfire or shudder under hard acceleration. have a feeling its a vacuum leak but cant find it using this scan....Any one else have this problem or can advise me, think the miss at acceleration could be coils, plugs are good...any help appreciated..

 

Don't keep doing it or it'll need at least one cat.

Cold trims are no good.

Fair chance it has the usual leak(s) - Search for terms like
elbow
hose leak
perish / perished

However, -ve trim means running rich so you may have some other fault(s). There again, +5 to -5 are near enough 0 not to worry much. I'd look at the hoses but may be bad coil(s)...

 

Thanks, will strip down and check vac pipes..what one will specifically create a rich mixture on one bank only?? Thanks in advance.

 

Start here:

https://www.jaguarforums.com/forum/s...ics-faq-52720/

 

Thanks all, a couple of pipes and 6 coils and all running sweet, passed the MOT!!!