L322 2002 v8 misfire

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Ruby Range

Ruby Range

Well-Known Member
Posts
338
Location
Sandwich Kent
Hi all I have a slight missfire on my 2002 v8 which i cannot seem to track down. Checked all coils and all ok. Cannot find a vacuum leak and checked pressure for pcv ( taking oil filler cap off) all good. Took the rear plug out on drivers side and found piñon the tip!!. Cleaned off as thought I may have dipped it somehow when putting in but still a problem. Runs fine on cold start and when above 1000rpm but still have bad fuel consumption. Beginning to suspect a bloody head gasket!! Any other ideas!! No management light on or code!!
 
Maf sensor I believe is good as all gear changes are good and I know that the maf also causes this issue but will have a code reader done on Wednesday and someone has mentioned the o2 sensor. My biggest fear is the oil returning on the plug when I remove it again
 
A compression test if in doubt of the gasket/rings or cylinders.
While on live data and engine running, watch the o2 sensor and spray a tiny amount of butane or a similar gas and watch the o2 sensors behavior change.
O2 sensor 1 bank 1 or bank 2. This determines the engines fuel mixture. O2 sensor 2 bank 1 bank 2 watches the cats behavior.
If you introduce a separate fuel through the air intake it'll change the behavior of the o2 sensors and they will react by adjusting the fuel intake.
If they don't react one or both are duff.
The black plug could be a valve stem, valve seal or rings on that particular cylinder (internal oil leak).
If the whole bank of plugs are black, say Bank 1,it could be down to an o2 or maf sensor.
Just because a sensor gives feed back it could still be under performing and having manufacturers specs can help to varify that.
 
I had a misfire after doing the cam cover gaskets, turned out to be a bent fuel injector electrical pin.

Not helped by the proper instruction of yanking the injector bank OFF and also the hefty pushing back ON.

(Oil in plug wells is common, fixable with new inner and outer cam cover gaskets, AND a functioning PCV valve)

Oh boy, the flashbacks.:eek:
 
Last edited:
Mark Piercy said:
A compression test if in doubt of the gasket/rings or cylinders.
While on live data and engine running, watch the o2 sensor and spray a tiny amount of butane or a similar gas and watch the o2 sensors behavior change.
O2 sensor 1 bank 1 or bank 2. This determines the engines fuel mixture. O2 sensor 2 bank 1 bank 2 watches the cats behavior.
If you introduce a separate fuel through the air intake it'll change the behavior of the o2 sensors and they will react by adjusting the fuel intake.
If they don't react one or both are duff.
The black plug could be a valve stem, valve seal or rings on that particular cylinder (internal oil leak).
If the whole bank of plugs are black, say Bank 1,it could be down to an o2 or maf sensor.
Just because a sensor gives feed back it could still be under performing and having manufacturers specs can help to varify that.
Click to expand...
thanks for the reply I am going to check the O2 sensors once I’ve changed the plugs and checked that the one plug that was oiled up is now dry
 
Ok so new plugs in no oil on top so all good. New plugs in and still a misfire. Plugged in my snap on diagnostics and came up with tank vent valve and p0443. Cleared all faults. and spent an hour pulling vent lines and things I have no idea about !!!. Start car up and ran ok for about 2 mins and now although a miss fire nothing as bad as before and now no faults just the tank vent. 2 questions really. Firstly could this actually cause a misfire and secondly where the hell is it !!!
 
Ruby Range said:
Ok so new plugs in no oil on top so all good. New plugs in and still a misfire. Plugged in my snap on diagnostics and came up with tank vent valve and p0443. Cleared all faults. and spent an hour pulling vent lines and things I have no idea about !!!. Start car up and ran ok for about 2 mins and now although a miss fire nothing as bad as before and now no faults just the tank vent. 2 questions really. Firstly could this actually cause a misfire and secondly where the hell is it !!!
Click to expand...
Who's fuel are you using @Ruby Range? Intermarche and eleclerc is not the best and do you do a lot of shorty journey's?
 
Yes quite a few short journeys but every third fill up I use premium fuel like texaco super. Will do a 30 mile round trip tomorrow and then see what faults it throws up. Anyone tell me where the fuel vent valve and purge valve are !!!
 
DOO ..on here had a misfire ,he striped the wiring loom to the changed ,maf cps coils leads ,then it started using water :eek:,,,,it was a head gasket in the end :( ,Have you tried a compression test ,are you losing water .any back pressure in header tank ...Hope its a simple fix...
 
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