Rover 25 losing revs when climbing gears

[Glyn1959]

Hi, my son has a Rover 25 (W reg) 55k miles. Intermittently as he climbs the lower gears the revs drop significantly. I have changed oil.oil filter and air filter (it was overdue a service anyway). The air filter was pretty clean.
He keeps the petrol level low (money!!) but not dangerously so for dirt to interfere (I don't think).
The car starts ok so I guess the alternator is doing it's job.
Any ideas what the cause may be? What should I check next? He's planning a 150 mile trip at the weekend and I don't want a phone call!!!

 

[Softus]

Intermittently as he climbs the lower gears the revs drop significantly.

Other than for the word "intermittently" I'd have said that this is normal, but I'm not sure what you mean.

Is it that the engine revs drop when climbing a hill in a high gear? If you feel that the engine doesn't have enough torque, then a service would discover the problem - when did it last have one?

The problem, if there is one, could be caused by any number of things, but check the condition of the plugs. Also, the fact that the car starts is no indication that the alternator is putting out enough volts at low revs.

 

[Glyn1959]

Thanks for the reply. When I said intermittently I meant ... it could run fine for a week and then one day when say going from 1st to 2nd or 2nd to 3rd, with foot to the floor the revs (and therefore the speed) are not there.
The plugs are next to change. However I need a box spanner or small extending socket set to repve x,y and z to get at them! I have never come across plugs so hard to get at!
Could I have dirt in the float chamber of the carburettor? If so how do I identify and resolve?

 

[keyplayer]

Why suspect a dirty needle valve? Do you have a strong smell of petrol from exhaust when problem occurs? I would suspect an electrical problem rather than fuel. Is the problem worse in damp conditions? Before stripping the carb, try running the engine in a dark garage. Using a garden sprayer, spray a fine mist of water over the ignition system. ie, distributor cap, HT leads and plug caps. Now can you see any sparking tracking across any part of the system? And you should be able to hear it as a sharp, intermittent clicking sound.