Peugeot 405 Injection came in from someone who had given up on the repair - it was running but not on all cylinders, but after a faulty electrical connector had been made good on a fuel injector a wire had been accidentally shorted to ground and it would not run at all now. And so it was delivered to us on the end of a rope to sort out. Tracing the cause of the non starting was fairly easy - the fuel injectors had all lost their live feed - this is supplied by the fuel injection relay and so this was located and the relay taken apart to inspect.Easily said that last sentence but in practice not so easy to do since to locate parts in cars nowadays can sometimes take longer than diagnosing the fault to start with. Anyway we found the relay to have been damaged by the accidental short, but fortunately it was repairable. The car then started up and sure enough it was running only on two cylinders. Numbers 2 and 3 cylinders were doing absolutely nothing. A compression checked revealed nothing amiss here and checking the electrical signal to the fuel injectors for these two cylinders checked out ok as well. The ignition spark to the offending cylinders though was pretty disgusting so  on to a more in depth look at the ignition. The system was a distributorless type and first the HT Coil was checked out, and then next the crankshaft sensor. Again Ok. The ignition Ecu though was a bit strange though in the way it operated - it worked as two Ecu's in one Ecu pack since it acted on each pair of cylinders, 1 and 4  then 2 and 3 seperately. It was found that the Ecu was at fault and replacement restored the running back to normal.

    Peugeot 306 didn't appear to be running to badly other than sounding slightly ragged at low speed, but it was only doing around 20 to the gallon, and felt a little rough on low speed acceleration. Tuning checks showed the exhaust gas to be much to rich, but because this was a catalyst equipped model this should not be possible as if the engine did produce too rich a mixture then the catalyst should clean it up to produce a clean exhaust from it.

   Unfortunately the catalyst will only cope with a moderate degree of over richness to it - beyond this and if left too long it will cause irreversible damage to the catalyst. First thing to do though was to correct the cause of the over-richness since a new catalyst would soon go the same way as the old one otherwise. Engine management systems checking revealed an oxygen sensor with a poor output - this sensor monitors the efficiency of combustion by checking the oxygen content in the exhaust, if it gives wrong readings then the fuel injected into the engine will be wrong as well. Removing the sensor an achievment on it's own since these sensors spend their working lives in a corrosive acidic mixture of hot gases and water vapour, revealed an oxygen sensor blocked with carbon deposits. The sensor was cleaned and re-fitted, this will sometimes revive it's performance, always good news because they cost around œ100 to renew. We installed an exhaust gas sampling line before the catalyst so that the mixture could be checked before and after the catalyst and re-checked the gas mixtures. Into the catalyst OK, but out of the Catalyst no improvement over the input. However a quick blast up the road and another re-check and the catalyst was starting to work a little again. Another few more miles and it improved enough to get through an M.O.T. Caught the problem just in time.

Hessitation, power loss. This type of problem can be one of the most time consuming faults to find because the problem often is only slight and the fault only shows up when the car is being driven under load.

One of the most commen causes of this is fouled or sticking injectors that can be reconditioned at less than tenth the price of a new set. For more information on injector servicing click on injector.