2001 Jaguar XJ8 308 V8 4litre Sovereign

[GNM]

Hello all.

Well going through a series of dash warnings recently, but most regular is the orange eng light on. Today, garage put diagnostics plugged in say....

PO171.."Bank one" too lean. (engines does "pink" quite a bit climbing, but have tried 99 octane fuel, and no difference!) Have checked for air leaks, but nothing obvious!

Diagnostics say all other is fine. Any ideas please?

REgards

Neil

[E-bmw]

Lean is either not enough fuel or too much air.

Start with basics.

You say there aren't any obvious air leaks, are there any not so obvious ones?

Get the injectors checked and report back.

[Richard-D]

E-bmw said:

Lean is either not enough fuel or too much air.

Start with basics.

You say there aren't any obvious air leaks, are there any not so obvious ones?

Get the injectors checked and report back.

How would you suggest he gets the injectors checked?

[E-bmw]

Not knowing his specific capabilities/those of his mates I wasn't too specific but he could build a rig & do it himself, there are lots of "how to videos" on youtube or he could take them off & take them to a local company to him that can do it for him.

[GNM]

Hello again.

Update today. Although earlier no lights or messages today (suddenly gone), later today I suddenly got a message "Restricted Performance" with eng light on again. When I brake the notice goes away but eng light stays on!

Whats going on one asks.

Rgds

Neil

[Richard-D]

E-bmw said:

Not knowing his specific capabilities/those of his mates I wasn't too specific but he could build a rig & do it himself, there are lots of "how to videos" on youtube or he could take them off & take them to a local company to him that can do it for him.

Pulling all the injectors then building a test rig or sending them off for test would be an odd first move. Particularly as there's been no mention of looking at live data in relation to fuel trims and lambda response. Are these engines renowned for injector failures to the point that it's not even worth doing basic fault diagnosis?

[Richard-D]

GNM - I would hook up the diagnostic again and look at long term and short term fuel trims (these will be in live data). Adding these together gives you your total fuel trim. If you have a vacuum leak these will be a large positive figure (>10%). As you raise the rpm (around 3k will do) the total fuel trim will become closer to 0 on a car with a vacuum leak. Make sure you take note of negative figures when looking at scan data as this is very important.

Edited by Richard-D on Wednesday 25th September 17:20

[GNM]

Many thanks for all your thoughts folks, especially the last one re diagnostic figures to look for.

Rgds

Neil

[GNM]

Thanks for info so far folks.

Re the diagnostic stating BANK 1...Which side is BANK 1 ?

Rgds

Neil

[GNM]

Hi there. Just doing more diagnostics as you suggested but no sign of "long term"info.
Short term bank 1 -5.45 bank 2 -1.55. Then changed to both equal then to both not equal again.
Which is which side re bank 1 and 2?

Rgds

Neil

[Richard-D]

I'm afraid that without the 'long term' fuel trims these aren't any use.

[E-bmw]

You should be able to read live data with the tags.

LTFT & STFT for long term & short term fuel trims respectively.

STFT should go up & down around 0% pretty quickly.

LTFT should do the same but in a lower frequency if that makes sense.

Any variation from this is frequently a good indication of what the ECU is trying to compensate for if there is a fuel/inlet issue.