Aaarrrgghhh!!! Misfire

[nathanwedge]

I have a multivan with a 2.1 mv, I've just put a new exhaust on including a new lamda sensor, I now have a mis fire which only seems to occur when the engine has warmed up! If I turn the keys off and restart it it seems to go away for about 10 minutes then return which makes me think it could be electrical. Also it's running quite sooty but that could just be the misfire. Any ideas anyone? Cheers in advance.

[REGGAJ]

could be this....http://www.brickwerks.co.uk/shop?page=s ... ory_id=122

[Ian Hulley]

Any ideas anyone? Cheers in advance.

Yep, post it in the Techy Forum AFTER looking in the wiki at the subsection 'Vanagon Syndrome'.

Ian

[nathanwedge]

It also has a Gatkat ? On it, I think I need to remove that first!

[nathanwedge]

Any tips for fault finding would be greatly appreciated rather than just throwing new parts at it!

[Ian Hulley]

Well the traditional way would be to do a system restore ... refit the old lambda sensor and see if that cures the issue ?

[nathanwedge]

Old lamda sensor dead!mwhats the chances of getting a faulty one? The exhaust is blowing still in places, would that have any effect?

[nathanwedge]

Old lamda sensor dead!mwhats the chances of getting a faulty one? The exhaust is blowing still in places, would that have any effect?

[California Dreamin]

Old lamda sensor dead!mwhats the chances of getting a faulty one? The exhaust is blowing still in places, would that have any effect?

Of course..the lambda / Oxygen sensor, measures the level of unburnt oxygen in the exhaust gases...any leaks will give a false reading to that sensor. The exhaust must be gas tight.

If this is a NEW fault since your last work on the van, then chances are that the fault is down to something you have done. Don't complicate the issue by looking at other things until you have eliminated those things you have done.

Martin

[nathanwedge]

Cheers Martin, I thought as much my self, I'm gonna spend the day working through every thing and double checking! It's bloody annoying when the simplest of tasks seemingly goes wrong. I've had the van just over a year and its been faultless up to this point

[California Dreamin]

As a side note* when the fault occurs try pulling the lambda sensor plug apart...so it runs in fail safe mode...this could be a way of pinpointing whether this is a Lambda 'over fueling' issue down to it being faulty or as we have said, incorrectly reading due to exhaust air leaks.

Roughly put...the oxygen sensor measures unburnt oxygen in the exhaust fumes...Unburnt oxygen (under normal combustion circumstances) indicates insufficient fuel in the burn, HENCE the ECU's reason for 'Richening up' the mixture (incorrectly in this case).

If you experience a 'Complete' breakdown of one cylinder (running on 3) then remove the metal shrouds from the spark plug caps as this maybe partly down to the ignition shorting to ground. Obviously the symptoms are subtly different.

Martin

[nathanwedge]

Been playing again and got the exhaust airtight, still the same I've noticed that the AFM is making a buzzing/humming noise even after the engine stalls is this normal?

[nathanwedge]

Martin, I found the tiniest of leaks in the joint next to the lamda, remade the joint and hey presto! Perfect running. Cheers for the advice I'll hunt you down at one of the shows to say thanks!!

[California Dreamin]

You're welcome mate....

Martin

[AdrianC]

still the same I've noticed that the AFM is making a buzzing/humming noise even after the engine stalls is this normal?

More likely to be the idle control valve - and, yes, it should.