VTEC 1.8 135K. Starts OK but feels lumpy from cold - almost like its not firing on all four. Once it warms up a bit the tickover when stationary drops to virtually zero (sometimes stalls), once fully warm runs ok but in stop start traffic tickover is erratic 500 - 1500 rpm up and down. Pulled off the distributor and it and rotor look very worn. What do you think, is this likely to be the problem?

Not sure what "tick over" means. Suspect it is hard to start when cold? Could be bad glow plugs. They "warm" the cylinders to get them up to temp before starting. It could also be that you are not waiting for the cylinders to warm up. I have a 2009 tdi. It has a light on the dash that goes on when I put the key in, but I have to wait for it to go out before starting the engine.

run fault codes and look for temp sensors --MAP/MAF sensor faults

Make sure the block heater is working. But with high altitude and cold air this is somewhat normal for a diesel on cold start. If the glow plug indicator light flashes off and on quickly in the dash you may also have a burned out glow plug(s), this also causes a poor cold start.

I suspect smoke is just condensation in exhaust from suiting overnight. The other descriptions sound like it needs an oil change (noisy clacky) and lumpy starting sounds like dirty battery cables - clean them top and bottom. ??- When was last "healthy" tune up? Plugs, wires, all fluids & filters? I'd start there.

Sounds like something is overheating then and possibly a sensor. Not familiar with Rovers but might be a problem with the CAS and/or CPS which tells the ECU the motor is running and when to fire. Also maybe the IAC is bad and when you go from throttle to idle it can't control it and allows it to die.

This could be all sorts of things..probably not the fuel system (it is VERY reliable, unless someone starts tinkering with it). From you broad description it could well be an ignition fault. I take it it gets lumpy as it warms up, so (in order of cost) replace the plugs (insulation breakdown), the plug leads (buy one long one and move it round the system). If you are loosing water, you may have a gasket gone.

Your oil is a little low, and the timing may be off a bit but if it smooths out after warm it is probably ljust
low oil.

If your coil packs have been failing this can also make the cat fail. I have heard of many instances of this happening. Get an emmisions test done. If the cat has failed dont pay mazda price get one of the net for the fraction of the price which is just as good

warm up the engine and turn it off then try to turn the crankshaft pulley with a suitable wrench. if its too hard to turn by hand then the bearings might be too tight.