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Discussion Starter #1
Background:
I've had issues with my MCSF light coming on. Mostly it kept flagging up P0300 misfire generic and P0302 C2 misfire, today it also flagged P0303 C3 misfire. I thought I may have had coil issues as the light always came on when warm.

Today I decided to check my lambda readings, so I whacked it on Multi and had a shufty. Pre-cat readings seemed normal. My post-cat readings were:
1 signal: 0.46V
2 signal: V (my first clue)
1 status: open loop
2 status: open loop

I thought the lack of a lambda 2 reading was odd, so I tried to manually activate them. 1 activated fine, but on number 2 the operation failed.

My conclusion is post-cat lambda sensor 2 is knackered.

Can anyone back me up on that? Or am I missing something?

It's a 2004 147 2L twinny.
 

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I don't know on your lambda readings but why didn't you move your coil packs about to see if the error moved with the coil packs? That way you could rule out a duff coil pack?
 

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Discussion Starter #3
I was going to but all my tools are in a workshop on the other side of the RAF station I live on...and its lazy Sunday haha. I'll give it a crack next time I'm over there. Normally I only get the C2 misfire, the C3 today was a new one!
 

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Ha ha fair enough I'm ex navy so know all about lazy Sundays :lol:

It might be something else but I would start with coil packs as it's quite easy to swap them about and it'll quickly be diagnosed as them or rule them out.
 

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Discussion Starter #5
Cheers Mike, I'll pop over the workshop this evening and do it; going to swap 2 with 1 and 3 with 4.

My money's still on the lambda though, my fuel consumption seems poor, although the fault's been present since I picked the car up a couple of weeks ago. Private sale, so no recourse. And hey, you don't buy a 147 for £800 and expect it to be perfect!
 

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Try cleaning the electrical connectors to coil packs with some contact cleaner spray, and while you're there do the same with the lambda connectors as these are known to cause issues.
Make sure they're properly dry before replugging and starting the car.
 

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Also I've been told that post cat lambdas are only there to monitor effectiveness of the catalysers and have no effect on air/fuel mixture so I'd say it's unlikely they'd cause bad mpg.
Misfire codes can be caused by faulty spark plugs or injectors. Have you replaced plugs recently and ran an injector cleaner?
 

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Discussion Starter #8
All 8 plugs were done on the last service, not tried injector cleaner yet.

I'll be swapping the coils around later in so I'll give the contacts a good clean too, as well as the lambda plugs.

Cheers!
 

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Discussion Starter #9
I really was barking up the wrong tree...my 147 only has 1 post-cat lambda sensor! A bit of googling trying to find the location linked to a thread on here stating that the twinny has 3 sensors; 2 pre-cat and 1 post. D'oh! I have swapped my coils around so hopefully that'll diagnose the fault as a nice cheap knackered coil. If it's not that then other than run some injector cleaner through I have no idea what to do!
 
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