Poor starter

My wife’s 2002 Ford Focus Zetec 1.6 petrol has suddenly developed a difficulty when starting. It has done about 140,000 miles. You need to crank the engine over about 10 times to get it going. Also, from cold there is initially a bad flat spot and lumpiness, but as the engine warms up, the running improves with a minor flat spot. When up to full running temperature, the engine more or less runs normally. I have just acquired a Foxwell NT200 code reader and it shows code ‘PO171 - system too lean - bank 1’. Richard Chappell

There are a number of possibilities, but as you only have the ‘PO171’ code and no misfire code we can hopefully dismiss the possibility of a faulty injector. Another candidate for low fuel pressure and the delay in starting is a weak fuel pump, but again this normally leaves a code for ‘low fuel rail pressure’. The fuel pressure regulator could also be faulty, but again this would normally leave a tell-tale code.

This suggests you have a faulty 02 sensor or an air leak from the inlet manifold gasket. As a faulty 02 sensor is unlikely to give the delayed starting you are experiencing, I would first check the inlet manifold for any leaks. This check should include the positive crankcase ventilation (PCV) valve, to ensure it is operating correctly. A faulty PCV valve often leaves an oily residue in the air filter housing, so this area should be inspected.

You have not mentioned any excess oil usage, which could indicate a worn engine, but it would be worthwhile checking the cylinder compressions to ensure that low compression is not the cause of the delayed starting.

To conclude, a leaking inlet manifold via either the gasket, vacuum hose or PCV valve would the areas to check first.