Somewhat complicated engine light fault

StewartIngram · 5th April 2024, 19:19

I have a 2003 KV6 mk1 auto Connie. I've been running similar since 2007, with 99% of maintenance/repairs done by me. I don't claim to know everything, but I think I'm right in saying I do know the cars, but always willing to learn.
All the cars have been fitted with lpg (by me, and checked over by the supplier after fitting). Though the original kit is a bit of 'Triggers Broom' with replacement parts over the years.
For some time now, I've had an intermittent fault. When using a bit of acceleration (not too hard), the 'Check Engine' warning comes on, followed by the yellow engine light. This only happens when on lpg, no problem on petrol. It happens around 2500 rpm or above (I can't be too precise), and if I lift my foot, the yellow light will go out, if I don't then it stays on. Checking with my Foxwell OBD scanner, I always get a cylinder 6 misfire.
Now, with a bi-mode system, this helps with fault finding. Almost always some items can be immediately disregarded, leaving only those related to lpg being left. (Sometimes though, a problem can show up on lpg before affecting petrol, such as a spark plug deteriorating, but I have checked those out anyway).
Iv'e swapped parts around between cylinders, but the fault stays with 6. I've come to the conclusion that it could be either a fault on the lpg ecu, or software related, but for the time being my laptop has decided not to talk to the lpg ecu, so my planned recalibration can't be done; I'm chasing that fault separately.
As for the ecu, it has miniature relays inside, which redirect the injector pulse away from petrol and on to the lpg injectors. I've had trouble with those over the years and replaced a few. I am actually constructing a box of external (better) relays to replace them all, but that is on hold at the moment.
However, unrelated, I put TOAF on via the obd socket, and found the balance vis had failed. I've yet to look at that - I've rebuilt a few over time and should have spares in the shed. The 2 vis on the car were actually brand new last year and I checked they worked after fitting. I know Stocktake (I think it was) does/did modified ones; does anyone know if it is him, and if he still offers the service?
Otherwise, although I've still got to recalibrate the lpg, and find my spare vis, has anybody got further suggestions?

SD1too · 6th April 2024, 07:04

Quote:

Originally Posted by StewartIngram

I put TOAF on ... and found the balance vis had failed ... The 2 vis on the car were actually brand new last year and I checked they worked after fitting.

Hi Stewart,

Check the balance flap for sticking in its mid position. This can be eased by light application of fine abrasive paper.

Yes, Stocktake can still help you if it turns out to be actuator failure.

Simon

5th April 2024, 19:19	#1
StewartIngram Gets stuck in Rover 75 Connoisseur 2.5 V6 auto Join Date: Jan 2008 Location: Chatteris, Cambridgeshire Posts: 907 Thanks: 320 Thanked 159 Times in 127 Posts	Somewhat complicated engine light fault I have a 2003 KV6 mk1 auto Connie. I've been running similar since 2007, with 99% of maintenance/repairs done by me. I don't claim to know everything, but I think I'm right in saying I do know the cars, but always willing to learn. All the cars have been fitted with lpg (by me, and checked over by the supplier after fitting). Though the original kit is a bit of 'Triggers Broom' with replacement parts over the years. For some time now, I've had an intermittent fault. When using a bit of acceleration (not too hard), the 'Check Engine' warning comes on, followed by the yellow engine light. This only happens when on lpg, no problem on petrol. It happens around 2500 rpm or above (I can't be too precise), and if I lift my foot, the yellow light will go out, if I don't then it stays on. Checking with my Foxwell OBD scanner, I always get a cylinder 6 misfire. Now, with a bi-mode system, this helps with fault finding. Almost always some items can be immediately disregarded, leaving only those related to lpg being left. (Sometimes though, a problem can show up on lpg before affecting petrol, such as a spark plug deteriorating, but I have checked those out anyway). Iv'e swapped parts around between cylinders, but the fault stays with 6. I've come to the conclusion that it could be either a fault on the lpg ecu, or software related, but for the time being my laptop has decided not to talk to the lpg ecu, so my planned recalibration can't be done; I'm chasing that fault separately. As for the ecu, it has miniature relays inside, which redirect the injector pulse away from petrol and on to the lpg injectors. I've had trouble with those over the years and replaced a few. I am actually constructing a box of external (better) relays to replace them all, but that is on hold at the moment. However, unrelated, I put TOAF on via the obd socket, and found the balance vis had failed. I've yet to look at that - I've rebuilt a few over time and should have spares in the shed. The 2 vis on the car were actually brand new last year and I checked they worked after fitting. I know Stocktake (I think it was) does/did modified ones; does anyone know if it is him, and if he still offers the service? Otherwise, although I've still got to recalibrate the lpg, and find my spare vis, has anybody got further suggestions?