Why the misfire?
Discussion
After a decent run out today on country roads in my Astra GTC 2.0 CDTi, I ran into a spot of bother with my car overheating (or thinking it was overheating). As I finally hit a long dual carriageway to make my way home, the rear screen demister turned itself on which meant I knew it was the car was running a passive regeneration cycle on the DPF.
The light stayed on for about eight minutes and instead of clearing, the car went into limp mode and sounded a warning tone with an 'engine overheating, switch off engine' message.
I did a bit of digging at the roadside and discovered it was likely an exhaust gas temperature sensor problem (it was). The engine wasn't unusually hot despite the dashboard coolant temperature being at max. On trying to restart the car, the warning message persisted and it misfired badly, stuttering and struggling to hold a steady idle.
After a short while I cleared the code with my Bluetooth OBD plug-in and the Torque app. It worked, and after a few hesitant attempts the car started again and ran fine all the rest of the way home. Figuring out the problem with the sensor was easy enough. What I can't understand is why the car was misfiring before the error code was cleared. Research online indicates that this behaviour is entirely in keeping with the fault, but I can't understand why. The only time I have ever had a car stutter and shake like that was a Volvo S60 petrol where the throttle module had failed.
It seems even more bizarre that Opel would design a car that would sit immobile at the roadside until a fault code was cleared, but that isn't unique.
The light stayed on for about eight minutes and instead of clearing, the car went into limp mode and sounded a warning tone with an 'engine overheating, switch off engine' message.
I did a bit of digging at the roadside and discovered it was likely an exhaust gas temperature sensor problem (it was). The engine wasn't unusually hot despite the dashboard coolant temperature being at max. On trying to restart the car, the warning message persisted and it misfired badly, stuttering and struggling to hold a steady idle.
After a short while I cleared the code with my Bluetooth OBD plug-in and the Torque app. It worked, and after a few hesitant attempts the car started again and ran fine all the rest of the way home. Figuring out the problem with the sensor was easy enough. What I can't understand is why the car was misfiring before the error code was cleared. Research online indicates that this behaviour is entirely in keeping with the fault, but I can't understand why. The only time I have ever had a car stutter and shake like that was a Volvo S60 petrol where the throttle module had failed.
It seems even more bizarre that Opel would design a car that would sit immobile at the roadside until a fault code was cleared, but that isn't unique.
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