Hi, just read you problem with your Micra. I would do the following the the respective order:

A) Service the car to eliminate issues with the ignition components. Use the correct spark plugs, this can cause problems such as yours.

B) Check for any air/vacuum leaks.

C) Have a garage or fuel injection specialist scan the injection system for fault codes and read live data, which can be very handy with issues such as yours.

let me know how you get on.

Hi, the car has just had a service, but no fault codes showed, despite the rough running. It got a lot worse after that, especially after I depressurised the fuel tank to change the pump. Since cleaning the MAF the engine light goes out and the car runs a lot better, so I thought I would go ahead with the MOT and see if it gets through the emissions test. I will check the plugs first, as you suggest, and get the garage to re scan the system and see if it shows up anything. Many thanks for your help

I think your problem may be around the throttle body area. You need someone to use a oscilloscope and monitor the output from the mass air flow meter. We are specialist in fuel injection diagnostics in the North West of England. If your car were to come to us, we'd begin checking the vehicle systematically from the mechanically side to the fuel injection. It really need to go to a diagnostics place otherwise you'll end trying all sorts of things and swopping bits which can be costly. Where abouts are you based?

I'm in Essex, I'm afraid. With the age of the car, I'm certainly worried about the cost of repair outwaying the value of the car. I'm coming to the conclusion that if the problem is not just cleaning or replacing the MAF, I might just stop there. Many thanks for your input

Glad I could help. well, I tried anyway. Good luck and let me know how you get on dude.

Got the MAF clean enough to get through the MOT emissions test. Will see how it goes, but managed to avoid the expense of a new MAF or throttle body. Many thanks for your interest.

Your problem IS most likely the MAF air flow sensor. Remove it again and immerse it in a plastic tub of methylated spirits for 10 minutes - do NOT use carb cleaner, brake cleaner, cellulose thinners, acetone or ANY other aggressive solvent - they will ruin the MAF. Shake the MAF around in the meths to remove any debris and tarnish then drain for 30 mins onto some paper towel. Use an air duster can or compressed air line to blow out any remaining moisture. Re-fit sensor to the car and you should now be ok. If not, apply the same treatment to the throttle position sensor (TPS) which is to the left of the MAF looking at the drivers of the throttle body (RH drive car). I have fixed this problem on 5 micras from 51 to 03 reg (K11 model) on both 1Ltr & 1.4 Ltr engines. Good Luck!