Rogue car of the week a Rover 820 obviously didn’t like Shopping at Sainsbury’s. or stopping at traffic lights. “I ran out of bread to make some toast so I had to pop down to get some, the car started ok but at the traffic lights going down the hill just before the police station it stalled and was hard to restart. Then when I came back out of Sainsbury’s it wouldn’t start at all.” Hmm, what sort of bread did you buy I felt like asking as maybe strange forces were at work here. Anyway it did restart eventually and when it arrived with us it was running alright. Normal tuning checks revealed nothing untoward so we kept the car overnight to check it out under cold start and running conditions the next morning. We had left the car with devices monitoring the Injection and ignition systems in readiness for a run to Sainsbury’s to check out this problem but the fault occurred before it got far out of the workshop. The cause was loss of ignition so at least we had narrowed the problem down to a specific area. Closer investigation of the ignition system showed the HT coil, plugs, leads,distributor cap, rotor arm, and Ignition control unit to be behaving but the output from the flywheel sensor to the ignition control unit was lower than normal. The sensor was checked against specifications and checked out ok so it was removed for closer inspection. And there the fault was found - a clump of iron particles stuck on the end of the sensor, reducing it’s output to the point where the presence of brown bread in the car was enough to stop it starting completely. The route cause of the fault though was the starter motor - the gear on this had been wearing badly transferring it’s debris of iron filings onto the flywheel sensor. With a new starter motor fitted and the flywheel sensor cleaned the motorised supermarket trolley was back in action again.

Emissions failure.  The most common cause of rich running faults is the lamna sensor or the ECU (engine control unit) both of these parts are relatively simple to check, to check the ECU strip back the insulation onthe signal wire from the lamna sensor, this wire is usually black.  Then hold the bare wire between you finger and thumb then touch your other hand on to the battery positive if the emissions come down then you have a faulty lamna sensor but if the emissions remain the same then the ECU is most likely at fault. For more information on ECU testing click on ECU

      The Rover 820 came in with running rough and underpowered.  This particular model of the 820 has a single point fuel injection system - one big fuel injector supplying all cylinders instead of the more common arrangement of an individual injector for each cylinder. The operation of the Injector and also the Ignition system is controlled by the engine management control unit and in

      order to alter the fuel mixture car we have to re-programme this control unit with a handheld tester/programmer. We tuned the car including reprogramming the control unit to correct the mixture which was way to rich but it still wasn't quite right. Then we remembered that the owner had told us that he used to immobilise the car using a hidden battery isolation switch. A good idea  but doing this with the Rover causes power loss to the control unit and causes poor running for a while as the control unit then goes through a re-learning process over the next few miles. We ran the Rover for the next 10 miles and sure enough the car came back to normal running. Another consequence of turning off the battery main feed that was not put right by the 10 mile run - the radio still didn't work. It needed it's security code putting in for it to work after it had lost power to it, and the owner was not given it when he bought the car. No problem though - we removed the Radio, connected it up to our Radio Decoding Computer and retrieved the code to reactivate the radio again.