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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21614
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Qashqai 2 litre auto 2007 runs fine minutes then develops

Resolved Question:

qashqai 2 litre auto 2007 runs fine for 30 minutes then develops a misfire.Fifteen minutes later is fine again
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
HelloThis sounds like an electrical actuator or sensor at fault .Usually when you can cycle the ignition key on / off and then restart the engine and the fault is gone temporarily this indicates that this is an electrical component causing this issue. This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;Airflow meterCrank position sensorCam position sensorO2 sensorThrottle position sensor unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40 and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins. Also its worth checking that the electric pump that feeds the injectors is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If the connections to this are corroded or damaged then the pump could stop at any time. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse, ideally measure the voltage at the pump and check its getting 12V Also check for exhaust leaks before the o2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate. this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers
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