2003 Vectra C z22se P0300 misfire fault

Thanks for taking time to help me Milo. I've purchased the Opcom off ebay, just got to wait a couple of days for it to arrive by post. Hopefully this will give me all the info. I require (I may need a little help working all the facts and figures out though!).

You are correct in saying that oxygen sensor 1 (pre-cat) is giving very erractic figures, so it may be faulty, or could another fault be causing the figures to dramatically drop down and up? I guess the opcom will give me the answers?

In the mean time I'm going to remove the throttle body and give it a full clean and check out the intake manifold fully for any leaks. Should I also remove the fuel rail and check out the injectors? I'm thinking one or more may be blocked!
I don't fancy removing the down pipe of the exhaust, so i'll have to take it to a garage for them to check for a blocked Cat!

I have noticed over the last couple of years that I have had to top up the engine oil frequently, it seems to be going through a lot of oil. I have had the oil low warning light come on a couple of times over the last 6 months, while doing motorway driving, so have had to top it up with a litre of oil. From looking around the engine bay, it seems that I may have or had an oil leak, as under/around the rocker cover there looks like oil residue. I also noticed a film of oil on the bottom of the sump, when I did an oil&filter change. I haven't noticed any pools or drips of oil on the road under my car. I guess I will find out more when I remove the rocker cover to check out the timing chain?

Also I noticed on my fault reader that the ignition timing advancee is stationary at -10 when idle, but it raises up when I press accelerator to raise revs. Is this normal?

Thanks again, any help will be much appreciated!
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I fitted a new Coolant Temp Sensor today, but it made no change, my Vectra is still running rough at idle and have low power/hesitation when driving under load. When I press the accelerator and it starts stuttering, I seem to have to change gear in order to get the car to accelerate.
This is a bit of a long shot, but worth checking both the fuel pump and engine management relays. Take them out and check the contacts for corrosion, clean up and smear some Vaseline on the contacts and replace. If they look distorted or discoloured then replace them.

Not sure where they are located on Vectra C or what colour they are (both are purple on Vectra B & Astra G, located in black box on top of ABS unit)
I received the Op-Com today, took me a while to install a driver on my laptop to get it working. Also wasn't sure what app to use with it! I got the Vaux-com app to work with it when plugged in to my car. This is a vid I took today, showing the data. I haven't found out anything more yet using the op-com to what my OBD fault reader shown me. Do you think that there is a fault with my Lambda o2 sensor 1 (front)?
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I fitted a new front oxygen/lambda sensor 1 today.. its made no change. Figures on the OBD Live data for the sensor is still fluctuating up and down quite rapidly. At idle it's still rough, reving and loud! I thought it would have been the Lambda sensor, but no I'm not that lucky!! I'm going to remove the throttle body tomorrow and check intake manifold, then over next couple of days, check fuel rail and injectors, before finally removing camshaft cover to check timing chain marks and I think I'll then find out where this engine oil has been leaking from!
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Having listened to the first video you posted a few times, I'm inclined to agree with Milo that the timing chain has either stretched or a guide has broken and the chain is 'slapping' about (could also be the balance chain).

I assume you have no history of the timing and balance chains being renewed. What's the mileage on it now?
The chains should be renewed every 10 years or 100,000 miles whichever is sooner as the guides become brittle over time and can break up with bits ending up in the sump blocking the oil pickup pipe.

I would recommend removing the cam cover to check for a slack chain, but you would be lucky to get the timing marks on the chain aligned at TDC, ideally you require the timing tool (KM-6148 or equivalent) to check the timing. If you were to remove the timing/oil pump cover this would reveal a lot more but then you are half way towards the job of installing new chain kits anyway.
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I would check map sensor again I cleaned one and when I took it apart I found the actual sensor inside had come loose and would move which caused my engine to do the same as yours I found if I pressed the back of it when the engine was running it would go crazy and shut off and that was on a engine that had only done 2oo miles
I removed the throttle body, gave it a good clean and checked the inlet manifold, it looks okay, but can't fully tell without removing it.

I also fitted another Map sensor and MAF sensor, but my car is still running rough!

Final jobs are to remove the fuel rail and check/clean injectors.
Remove the exhaust down pipe to check for a blocked CAT.
Remove Cam top cover to inspect the timing chain.

It must be one of these that's causing me a lot of hassle!!?
I broke down yesterday! I started the car ok, reversed out my parking bay, but I hardly had any power, I went to pull away and the car cut out. I managed to restart it after a few tries, but it sounded as if it was about to stall, reved it for a minute, but then when I went to drive off it cut out. A friend of mine said there was black smoke coming from the exhaust. I now can't get the car to start at all, it's trying to start/turning over, but not starting. I presume the timing chain has now gone!!

I was hoping my problem was going to be a cheap fix, just a bad sensor, injector or air leak causing misfires, I was hoping it wasn't the timing chain, as the car was still drivable.

I should have took the cam cover off and checked the chain before anything else, but I was waiting for a new cam cover gasket to arrive by post before I took the cover off, as there has been oil leaking. I was also waiting for a friend of mine to be free, who is an ex mechanic, just in case the chain just needed re-aligning.

I guess I'll soon confirm if the chain has snapped/come off, when the cam cover comes off this weekend!!
Craig, that doesn't sound too good. :(

Don't try to start the car until you have removed the cam cover and checked the state of the timing chain.
If the chain has broken or jumped a couple of links, valve damage may have occurred and valve guides may possibly be cracked as these are 'interference' engines.

Edit: post some photos or a video so the experts (evocarlos or vocky) can advise.
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I finally managed to get the cam cover off. I've took a few photos. It seems like the timing chain is the fault! It's loose and looks like it's skipped a few links, according the green mark on the chain?