Hi there everyone.
I'm the 'new' owner of a 3.2 omega as of 3 weeks now, and until very recently has served me very well. The car came with a good history (recent service/timing belt kit change/exhaust), and upon inspection was very clean. It in fact still runs perfectly well at the moment.
However a few days ago when I lined up to overtake a lorry going up an incline on an NSL road, I pressed the sport button and accelerated sharply to overtake. As soon as this happened the EML came on and I was limited to 2k revs and it sounded like a couple of cylinders were misfiring. When I could, I pulled over and switched off the engine and looked under the bonnet. Everything looked perfectly fine, so I started it up and it ran fine once again with no EML. But the dash light with the spanner through the car now became illuminated. It has remained in this state for the last few days, running seemingly perfectly normal whilst putting on a few hundred miles including two 5 hour round trips on very mixed roads.
I've since reacquainted myself with the service history of the past owner, and found that the timing belt kit change and service had been done at the end of last year at an independent. Around the same time Kwik Fit (:/) had also replaced the exhaust. And more recently the last owner had taken the car to the Vauxhall main dealer to get rid of this warning light (spanner through the car) to the tune of £450, replacing the lambda sensor and another sensor which I have the part number of.
Having read through some of the guides and had a search on this site I managed to utilise the pedal trick to get some fault codes:
0130 & 0150 - Both lambda sensors
0170 & 0173 - Both banks, fuel trim malfunction. MAF?
0300 - misfire detected
0304 & 0306 - cylinder 4 & 6 misfire detected
1110 - Intake manifold valve
Seems like the vauxhall monkeys didn't do a good job of finding the fault, as both lambda sensors give errors now. And as both banks of the fuel trim are malfunctioning it leads me to believe something that runs before these components is at fault. Your ideas?
The engine actually sounds and seems to run fine with no dip in performance since that attempted overtake in sport mode, although I haven't tried it in sport mode since! So will the fault code be produced because of that isolated incident, or is still misfiring now?
The only thing I can think of is that the MAF perhaps needs replacing? Also the fairly recent change of the the exhaust back box could lead to the lambda sensor trouble, does that mean a new back box is needed? Or can the MAF be at fault for that too?
As I say the car seems to run perfectly fine since that isolated incident and had covered over 500 miles in about 5 days without complaint. I also started to use premium unleaded as my dad had a similar issue with his 7 series, his engine would go into limp home mode sometimes under sharp acceleration until he changed to premium unleaded. This is why I have been running it since.
If anyone has any ideas what could be at fault I'd be very happy!
I personally think it's the MAF at the moment which is causing these fault codes, but if there are other things I should be looking at please let me know.
Kind Regards.