Coil packs not as healthy as they once were ?
Showing any codes ?

BTW: I'm not getting e-mail notifications for my posts.

Any codes? Pedal trick? Lights on dash? Fuel trims ok? Did it get progressively get worse over time....?

Quote:

I've just picked it up from my mechanic to correct a misfire which was down to oil in the plug wells, so haven't had a chance to check for codes.

It does suffer from the V6 pre-cat problem so the emission light is normally on (reset at the moment).

What are fuel trims? is that the offset in the LPG ECU?

It did progressively get worse, although it now seem to have stabilised i.e. at first, it didn't happen every single time , but now it does - unless I do my trick.

Fuel trims are the amount of positive or negative duration applied to the fuel injectors on each firing cycle. The engine ecu adjusts the duration according to the mixture that the o2 sensors are seeing in the exhaust. If it's rich it trims back the injector duration giveing less squirt per firing cycle giving negative fuel trim. Lean it applies positive fuel trim to give more fuel. Fuel trims.

With LPG, if the set up has an issue, causing the excessive fuel trim on gas only, then when it switches to petrol it immediately has to go back to the correct fuel trim which takes time as the trim level is worked out as an average over a period. This is long term fuel trim. Which, if it has say +25 % of lt fuel trim on gas will bring the engine light on, and will run very grumpy on first stater up on petrol first thing.

Switching the gas off 5 mins from home will bring the fuel trims in line enough to make petrol running better. Although it takes longer for the trims to be correct due to it's average learning.

It's possible the trims are far enough out to cause a starting issue IMO. It needs a look at live data and codes on petrol, then see how the gas affects it and adjust accordingly.

Work to do. Sortable though.

Might be worth getting your mech to get a code reader on it. See what fuel trims and codes are doing first. Clear codes and see how it goes, assuming the faults are fixed.

There are other threads from the op discussing other issues iirc...?

Yes, I can see what you're saying and it sounds quite reasonable. When I had the LPG installed, they did ask me whether I wanted it set up for power or economy; I chose economy reasoning if I wanted more power I could simply switch to petrol.

So, just freethinking here: I guess my LPG ECU is setup lean, the Engine ECU compensates by richening the mixture; therefore when it stops on LPG and then starts on petrol, it's running rich...

...except, despite everything I said earlier, I have just realised it doesn't start as though it "has the choke out", rather the opposite. Perhaps it's all the inverse of what I said, which still points to fuel trims.

I forgot to mention one other thing, As it starts, warms up and changes to LPG, it progressively runs rough and nearly stalls (the engine light flashes). If I immediately change back to Petrol then back to LPG, it runs smooth. If I don't interfere it eventually sorts itself out.

Definitely sound like fuel trims.

I'll do a pedal check on my way to work tonight.

Next step: Are there other readers that can read fuel trims live or just a Tech II?