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Missfire (on going saga) Help needed please


Willsy1980

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Right, where to start...

 

Few weeks back was on the M'way doing 70 uphill, needed to accelerate so powered on to 80, 85 and it missfired logged codes 0300 and 0303 Random and Cyl 3

So, thought plugs. Replaced all the plugs, they were pretty knackered looking and no oil in wells etc.

Drives fine round town, missfires like hell at M'way speeds but no codes, so thought coils.

Replaced coil 3 with a new NGK from Alex (only did the one as that was the highlighted cyl) 

Again, fine round town, crap on M'way.

 

Today, got 5 second hand coils tested them with Mulitimeter resistance of 1.3 on pins 1 and 2  for all coils so all good. 

Stripped it down to swap them all over barring number 3.  Had a thought to test mine on removal, all come back with 1.3-1.4 on pins 1 and 2 and the new NGK had 1.2 so all good ??

I also undid all the plugs, Cyl 5 seemed a little loose. Torqued them all back up to 24nm popped coils back in put everything back went for a drive.

 

Drives perfect round town, got on the bypass booted it to 5000rpm in 2nd, 3rd, 4th, fine. Popped it through 5th into 6th upto 100mph (private road obvs) and it threw flashing CEL again, so stopped at asda read code, p0300 so random on 1 or more again....  so cleared it popped reader in to missfire mode drove home no issues and nothing picked up.

Yet idle is fine, round town fine pulls through range fine and not logging code again.

 

Im now stumped. Any advise ?

 

Do I run a cleaner through it ? buy new injectors ? is it just knackered ?

 

Sorry for the long post but im losing my mind on this now.

 

Steve

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Check your engine earths - especially the one on the top front above the power steering pump - its the end earth point for the coil loom.

It's only a 10mm bolt into the front cover but the ally corrodes take it out check the wire for damage give it a clean and put it back on.

There is also any earth to chassis on that side make sure it's good.

May not be it but won't do an harm :thumbs:

 

Good luck

 

 

Edited by Keyser
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Sorry to hear your problems. Lots of things it could be. I chased similar issues for a while. It only went bad when booting it and then it would throw the random code. Turned out it was a Cat breaking down. The honeycomb stuff had come loose and it couldn't flow the really high volume of exhaust .. 

Like above, it might not be that but it's a quick check, shake the exhaust

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Thanks for the suggestions, at least these are a quick and easy check, if its the cat would that give a more smelly exhaust too ?

The earth above the PSpump, where does that fasten too ? 

Edited by Willsy1980
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