If you have high O2 levels with a rich mixture, perhaps it might hit an instability and still have high O2 levels, even with lots of fuel. This was one of the reasons I suggested a rolling road run at the start, or even getting the car hooked up to another lambda sensor / exhaust gas...

Glad to hear you've got it almost sorted. Just a small point, did you have any diagnostic results that told you the coils were failing? Or was it only swapping them that showed that they weren't working properly? Have you tried reconnecting the lambdas since doing the coils packs? Poor...

Once you have checked the voltage profile at the injectors and if you find any discrepancy, you need to work back to the voltage output and earth, both the +ve voltage side and earth 0V side to work out where the voltage is being dropped, or if the ECU wasn't providing it in the first place...

If you have several injectors working off the same lambda signal, one injector going wrong will start to give misfires on that cylinder first, if there is a limitation as to how well the LPG can work down to very lean mixtures, it burns very easily, but even LPG has a limit as to what mixture...

Your logic is a bit skewed. Lambda sensors do not switch. They provide a voltage output depending on the O2 concentration in the exhaust gases. The ECU is detecting the voltage output that the lambda sensors are generating - 0.35, lean, and as the fuel trims are +28%, it cannot get enough...

I know you have said that you have checked the wiring, but if cylinder 4 has a problem, there might be a dry soldered joint in the loom for that one cylinder, where the LPG system wiring has been spliced into the normal petrol loom. You would need to resolder the joints, even if they...

The importer for Romano systems is Autogas Worldwide, or MINT LPG. They have their main place at Newport. Their website is MintLPG - Autogas LPG Conversions by The Experts It could be the LPG injector for cylinder 4 is failing / sticking. There is a filter in the LPG system that does need...

Try ringing The ECU Doctor as a starting point, perhaps they have had a RR ECU with the same problem, with the lambda /closed loop mixture control circuit/chip failing.

Did you check the continuity of the lambda sensor circuits from the plug that goes into the ECU? If the continuity is there, then it is either the lambda sensors (chemically knackered / reacted with something bad) or the ECU itself. I've been running a VW on LPG for about 2,500 miles now -...

Do you know someone with a good ECU, who is willing to let you swap over? Try and get another one from a breakers yard and see if the same fault develops. Have you changed the lambdas again? Or tested them on another vehicle? Have you got a friendly garage who will plug them into someone...

If the wiring with the LPG stuff has a problem, then switching one or two injectors might not be working. How well have you checked the wiring to the LPG ECU and all injectors?

LPG ECUs are easy to check. You need to go to a dealer for the LPG system and ask them to swap the LPG ECU. How old are the LPG injectors? They could be malfunctioning. Lambda sensors and ECU work together in a feedback loop, where the signal/mixture, if rich, tells the ECU to lean...

Sticking rings? Sounds like an oil specification problem, or oil change frequency problem. Top spec fully synthetic oils don't give ring sticking, but then if the engine metalurgy/design is poor, even allowing for proper lubrication, it's not surprising that the V8s have to be rebuilt at...

I don't know the specific trigger system in the dizzy, but my dad actually had a fault with the earth wire connected to the base plate (points & condenser trigger system) cause a misfire, back in the 70s. How well did you rinse the tanks out before you put petrol in? If you didn't it...

There is a valve that lets fuel into the carburettor bowl, that is operated by a float. You might need to strip the carbs down, clean them out and possibly replace the valve. Alternatively, you should have an inline fuel filter fitted and you might need a fuel pressure regulator, just to...

Check your plug gaps. Did you get the leads off and did you pull any and damage one? - check their resistances

With some cars, with emissions control EVAP systems, you have to be careful how much petrol you put in, because you can knacker the charcoal cannister with getting liquid fuel into the pipe and system that was designed to only deal with vapour. I don't think this is your problem, but it is...

I've actually been having a problem on another vehicle, and you have actually prompted me to look at that part of it, but on mine, everything was renewed. Might block mine off for a bit as it might be a resonance problem on mine, yup, it is that type of wierd problem.

This is getting better actually. If the mixture had been made rich by the fuel trims being altered, then they could go rich. This could be an airleak relating to a crankcase ventillation pipes or valves. PCV valves are designed to control the airflow through the crankcase. If the pipe...

If you did the standard fuel pressure testing when stationary, it might show up as normal and not a problem, but it might be the wrong result because that test would not be under the same conditions as when the problem occurs i.e. when driving.