My Classic starts first time, Runs very well on road for about 5/10 minutes then starts running very rough including backfiring lumpy as hell. After I pull over the engine ticks over over fairly well. If you blip the throttle it really doesn't like it, very uneven running. Eventually it clears and engine runs very well.
I stop for a while and the engine cools down then it is slow to start and the running rough starts all over again untill it totally warms up. Any suggestion? I am looking at the automatic choke because this sort of fits with the engine getting up to temperature then problem starting.
Could be as simple as a blocked crankcase breather assuming you have fitted the correct spark plugs, plus leads & coil and the connectors are OK. Then you can think about testing or replacing the EFI engine temp sensor.
I had a similar issue on my 1987 3.5 just after two years of ownership and in the end the engine but would start again, so took it back into my main dealer for its annual service and mentioned my issue, although rocker cover flame trap isn’t listed as a service item the service department replace it.
Anyway, as the flame trap was only item to be added to the bill for the basic fluid change service so I could only take at the time that was the cause of my issue.
But 6 or so years later the issue returned, so I fitted a new flame trap and washed the hose in petrol, instantaneously the engine was back to normal, and still no issues when sold in1997.
The old flame trap was cleaned in petrol and place on the shelf, just incase my disco had a stalling issue, but it never has although now 25 years old, but then spin off the flame trap wash it and refit when I feel like it usually at an oil change.
As for the RR 9th injector on the 3.5 EFI the only information at the time was a guess, no forums then, just a main dealer RR owners club, it was intended just in case the vehicle went into the northern hemisphere where winters are cold, out of interest I did eventually read what the the ambient starting temperature would be for the injector to function… so a long while ago… but could have been something like - 25c
I was always suggest as the reason for the the 3.5 difficulty in starting, even when the owner stated the electrical connection was unplugged… so not much different from some forums now.
