New battery

I think I need a new battery for my 2001 Ford Puma 1.6 with the Zetec SE engine. The engine has done 142,000 miles, doesn’t have any service history and has a misfire, especially when going round corners. I did the test procedure where you press the trip button and turn on the ignition, which takes the car into test mode, and it stated that my battery has 11 volts. This could be why, when I try to start it, the needles sweep over to the maximum on all dials. The car does start, but very slowly

I have fitted a new air filter and used some injection cleaner, after which it was slightly better. I checked the plugs and they seem OK, as do the leads, but they’ve only been inspected visually. There aren’t any fault codes stored, but there is a slight exhaust leak where the middle box joins the rear box – this looks like a nightmare to get off, as the bolts that go into the cat are real rusty. The car is due its MOT soon, the rear sills are rusty and the jacking points won’t hold a standard car jack, but it passed like that last year. Steve Cloke Starting with the battery, this does seem to be below par. You should check the charging to ensure that the battery is charging correctly. You did send me a link to an 075 heavy duty battery and this should be suitable for your Puma.

Although the exhaust leak will need to be rectified before the MOT and it may affect the emissions, it is unlikely it would cause the misfire you describe. As the misfire is worse when cornering, this may be due to a failing HT lead which is moving, allowing it to short out. HT leads are very difficult to test visually, but looking under the bonnet when dark may help. With the engine running look for any signs of arcing to earth – this may be a light blue or orange flash. If this is seen, the leads should be replaced.

The MOT tester will check the body to ensure that no area is “damaged, corroded or worn to such an extent that its strength is seriously reduced.” If your vehicle cannot be jacked up at the jacking point, the tester may deem this to be a failure point. This will depend on the vicinity of the corrosion and its affect on other points, such as the seatbelt mounting points.

Corrosion is a continuing process and the vehicle will most likely have deteriorated since last year, even if there has been little visible change.