Dreaded check engine light

[vitesse]

As per title, the warning light has come on and looking for ideas please. Fault code lists bank 2 (closest to bulkhead?) so trying to use logic - what would cause hesitant starting and lean on one bank? Thought of extra air valve so swopped whole throttle housing for another - no better. Lambdas are shared so should get the same on both banks (?). Next idea is whipping the upper manifold off and checking the 2 yr old spark plugs. No evidence of air leaks, both breathers secure.

The car had a good run for about 2 hrs motorway, and next morning hesitant to start with check engine light. Tickled the throttle and it came to life. Light still on.

FOC fitted, but if fuel pressure surely both banks would flag up?

Only got a 2 sp fan so fan error can be dismissed.

Thanks for reading

[SD1too]

Hello Mike,

To answer the uncertainties (marked ?), yes bank 2 is the right-hand bank nearest the bulkhead and I would expect your KV6 to have two lambda sensors, one in each exhaust manifold.

As the condition is restricted to the RH bank, common systems can be discounted.
Removing the plastic manifold chamber is a good idea to check the seals between it and the RH bank inlet manifold.

As always, keen observation and checking basics are good routes to a diagnosis.
Sorry that I don't have one for you!

Simon

[vitesse]

Thanks Simon, I had no hesitation using the word "dreaded" as this fault is so non-specific and could be virtually anything. I plan to whip the upper manifold off to get at the rear spark plugs and will have a look at the seals at the same time.

I forgot to add in my description that I do have a T4 if anyone thinks that would give me more information than Toaf. I haven't used it as Toaf is easier to connect and the T4 will wipe all my Toaf customisations (but easily restored).

The "short to V batt" doesn't make much sense unless it's referring to a lambda but then again it's just the one bank.

Keep well,

Mike

[trikey]

Check for damaged wires on the rear lambda sensor where it passes near the exhaust heat shield.

[vitesse]

Originally Posted by trikey

Check for damaged wires on the rear lambda sensor where it passes near the exhaust heat shield.

Will do, managed to drop a spanner which is now on the undertray, so can do that at the same time.

I thought about the Lambdas but would have guessed that would show up on both banks, but cars and logic don't often work together

Checked fuel pressure too which was good at 3.5 bar.

Thanks

[polinsteve]

Originally Posted by trikey

Check for damaged wires on the rear lambda sensor where it passes near the exhaust heat shield.

I would do that, but if nothing was obvious swap over the lambda sensors. If the fault moves to the other side it would pretty well confirm a dodgy sensor.

[vitesse]

Thanks for the input. I checked the wiring when I had the undertray off and unfortunately no signs of chaffing. At the moment I'm in the process of refitting the upper manifold having replaced the rear spark plugs that were only about two years old but I couldn't think of anything else which only affected the one bank. One of the spark plugs was a bit oily but the gap and electrode were good. Had to give my back a rest and will resume tomorrow.

I've got a donor so if the plug change doesn't help I'll swop the lambdas, but it means towing & pushing the donor into the garage where I've got a pit, think it'll be worth the effort as sometimes these lambdas don't want to move.

Thanks again