Cars been hunting on tickover, slow to pick up on acceleration, thought it was a suspect plug so took them out for a quick check over. Three looked good, the one in cylinder 4 dry/sooty. Fitted new and fired up, quick blast up the road, no change, cylinder 4 still sooty.

Checked the leads etc etc all fine, good spark at each plug. I removed the injector connection to cylinder 4, no change to engine at all! Rough idle still hunting. Seems like a faulty injector to me. Interestingly the Lambda sensor failed a while ago, I've heard this can be linked to a faulty injector???

Anyone had similar problems - the injectors are pico 042's and a bit pricey so hoping there's something else that I've missed.

Cheers

Steve

Try swapping injector for another cylinder and see if the fault follows, just incase it's something on the ignition side or even mechanical on the suspect cylinder.

Could also plug a 12v LED into the injector plug and watch it flash as the engine is cranked or run to check the wireing to its correct (observing polarity on injector plug and LED etc, think I read that's the best way to test them as multimeters don't really react fast enough)

In addition from swapping the injector over I would advise doing a compression test as the symptoms are also those of a valve not sealing.

a Noid light is the tool for checking injector supply/pulses, pretty cheap to buy. my suspissions would still be a coil pack fault. may spark acceptably in atmospheric pressure but the presures inside the engine when running make much higher demands on the ignition system. swap leads on paired cylinders and see if misfire moves to number 1. changed many more coil packs than injectors

Worth checking the resistance of the injector and comparing with the others. If its different then you will need a new one.

Thanks for the suggestions, I'll have a tinker and see what I can find

Another suggestion, have a smell at your oil, if you can smell petrol you may have bore wash, ie petrol getting past the rings into the oil due to poor combustion.

If you can smell a strong smell of petrol change oil too.

The test you have done only proves that cylinder 4 is misfiring, it certainly doesn't mean the injector is faulty. To be honest injector faults are uncommon compared to ignition or compression problems.