01 v70 2.4t misfire on lpg
 

I have a 2001 v70 2.4t auto on a Vialle LPi system

On petrol it runs well and pulls hard through the rev range.

I've recently replaced the plugs as a baisc service was needed and the car is new to me. Also because on LPG under hard acceleration I noticed it was missing and losing power.

Flashing ECU light. Turns out I've got a misfire on cylinder 3. Got 2 good used coils. Replaced cylinder 3 twice with known good coils. Still persists.

When accelerating on LPG and giving it full throttle it will bog and miss, switch over to petrol it's like turning on a rocket booster. So it has to be LPG fuel delivery.

Ideas?

LPG needs a stronger spark than petrol so any weaknesses in the ignition system will be more apparent when running on gas. Volvo branded spark plugs seem to be more suited to their engines that other brands (based on what I've read on the forum) and usually when using standard plugs, the advice is to reduce the gap by 0.1mm.

Worth also getting LPG system serviced and possibly retuned. I can only comment on BRC and Prins systems that I've got, but sometimes you need the technician to tune the system via the laptop while car is being driven to get it to run seamlessly. I'd previously had my BRC system setup 'perfectly' on the emissions analyser but when trying to drive the vehicle, it wouldn't pull the skin off custard, but a 20 minute blast round the countryside with the chap updating the mapping in the ECU returned it to full performance.

Yeah if your ignition has a problem LPG will find it.

I fixed it today actually. I did a few things so I can't say for sure what the fix was but I'm pretty sure it was a bad Lpi injector.

It now pulls strong on Petrol and LPG

What I have done in summary:

replaced all plugs with Bosch plugs

replaced coil on offending cylinder (twice).

Today I replaced the brand new Bosch spark plug with a genuine Volvo USED part. Just on that cylinder. I also replaced the LPi injector on the offending cylinder and shuffled the coil packs around as I read about the inaccuracy of the specific cylinder being identified as culprit for missfire.

Took the car out and it ran better than ever. Fantastic.

Absolutley. Cheap plugs are best. Narrow the gap. Daft LPG plugs, are just a waste of money, and multi-point things will not work, or not work for long.

Iffy coil-packs will work on petrol for thousands of miles but will throw a hissy on gas.

I don't know if it was the plug, coil or injector at this point. Although, the plugs are brand new cheap bosch one's and the coil had been replaced twice. So my money is on the injector.

I think for the sake of clarity at some point I'll switch back to the Bosch plug and see how it does and same with injector

Oddly, only yesterday and yet again, I've replaced a coil-pack. Must be the third or fourth I've done to date. I've built a stock of them! Maybe you're not done with them yet?

You've got it working better than ever - leave it alone !