VR6 misfire (dizzy model) only in first / second gear under light acceleration

[oxfordpaul 0]

Hi Guys, as per title I have searched the forum and cannot find a similar problem. Basically when the engine is hot and idling at traffic lights, when I move off there can be a violent misfire. It never stalls and slipping the clutch (to increase revs) seems to help. It's worst when accelerating fairly gently like when in traffic. Any ideas? I've had new leads recently and the engine is the smoothest I've had on a Vr6 apart from this. It doesn't always do it and has not got any worse in the 12 months since I first experienced the issue.

[robrado974 1]

Remove the dizzy cap and check the inside of it , they are prone to moisture ingress . Mine was doing the same . When I checked the cap , there were arcs all over it . Once I fitted the new cap all was well.

[fendervg 30]

Ditto - and did you replace the lead from the ignition amplifier to the dizzy as well? Sometimes it gets forgotten. No harm sticking a new rotor arm in there as well.

[bruny 0]

Hi, remove the dizzy and check the securing pin holding the locating block, which locks position onto the camshaft lugs, isn't slowly dislodging. I had it on mine to the extent of barely being able to remove the dizzy. If it drops out it falls into the timing chain… ouch. It was a reconditioned distributor and I guess they hadn't lactated the pin in place.

[oxfordpaul 0]

Thanks guys, will check out these suggestions but deffo replaced the lead to the amplifier.

[oxfordpaul 0]

All looks clean and as it should be and securely fitted so don't think the issue lies there. What about the various sensors, cam position / engine speed?

[robrado974 1]

Those to sensors don't really fail to much . I would start at the coil and work my way to the spark plugs . Check every lead and electrical plug , inc the big connection plug ( I can't remember what it's called ). Use electrical contact cleaner on each male /female connections .

[Allan_T 10]

Do the symptoms ever occur when cold or when left standing overnight? It would be beneficial to determine if this is a single or multiple cylinder misfire, heat soak into a ignition coil can result in a coil winding that fails under load but will ohm out perfectly when tested with a DMM. A coil fault would affect multiple cylinders as would rotor arm and coil lead. There's the possibility a DTC has been stored for the misfire event but a secondary ignition waveform and primary coil current ramp would help pinpoint the root cause.

[oxfordpaul 0]

Hi Allan, no it's only when hot and usually when stop start in traffic. It idles perfectly and once beyond low speed / revs it's fine, it's just the initial take off that is really jerky, almost like it's been switched off for a split second.

[fendervg 30]

Maybe give your throttle body and cable a good clean and check the settings. It worked for me on my car. Runs like a dream now.

[oxfordpaul 0]

Hi, thanks will try that, but when you say check the settings how do I do this?

[fendervg 30]

There is a rubber stop for when the cable is at rest and this is meant to ensure smooth return to idle. There are also sensors on there that feed into the engine management. Have a look and it makes sense. You may need to take your top engine covers off to get access if you have a standard setup.

[oxfordpaul 0]

Thanks mate I will check out tonight, would be great if I can sort it!

[oxfordpaul 0]

Hi again, not sure if I sorted it, there is a plastic canister with some sort of foam in it and 2 pipes, this has basically fallen apart so presume maybe let air in and cause a misfire? Not sure what it does. Anyway I've taped it up and so far so good. the part number is 021 123 429 if that helps anyway understand what it is and what purpose it serves?!

[seanl82 23]

Under the airbox? if so, its the charcoal canister. It can be removed, but you'll need to plug the lines iirc. Have a search as I'm sure its been covered before.

[fendervg 30]

Ok - that is a breather/filter for the idle control valve - it's a common failure at this age as the plastic goes brittle over time due to the relatively high temps under the bonnet and cracks with age. Oil can also get in there and contaminate the foam.

 

They're not strictly necessary, and many people delete and bypass it, but a replacement can be got easily online if you search using the part number for about £50 or less if you decide to keep it as God (VW designer's) intended.

 

Your ISV will now likely need to be cleaned as well.

 

The charcoal cannister is for the fuel system and is different, but can also be removed, but it is a bit more work. If it's working now, there is no need to mess with it.

Edited August 8, 2016 by fendervg

[oxfordpaul 0]

Thanks, it is the breather filter and I've ordered a new one from VW, hope this has cured my misfire! There is oil in there so yes maybe ISV clean due but how do I do this? Is that the silver cylindrical thing? Sorry I'm not very mechanically minded. Also there is a pipe coming out of the far left hand rear top side of the engine with a rubber hose coming out of it held in place by a circlip. When I look in the pipe (metal) there is a mess of fine coiled metal, almost like a heater element that's been messed up with a screwdriver, any ideas?

[oxfordpaul 0]

This is the pic, what is this wire in the tube, should it be there?!

Edited August 10, 2016 by oxfordpaul

[oxfordpaul 0]

And I have also found this throttle stop (in pic, the orange coloured thing), this is sticking so stays down when the throttle is opened, what does it do and is this a problem? Once I lift it by hand it then seems to work but obviously if left overnight it's sticking down.

[seanl82 23]

First pic shows wires going into your cam cover. Certainly should not be there! I'd recommend taking your cam cover off to check for damage to your tappets and valve seats if anything has dropped in there. Either way, it's not good.

 

Second is the throttle damper. It's there so when you Throttle returns to idle, it acts as a buffer to avoid sharp decreases in revs and cutting out. It shouldn't go all the way up, but should push down slightly with a bit of force.

[oxfordpaul 0]

Thanks Sean, I did think the wires were a bit strange, how on earth have they got there I wonder? It doesn't seem to affect running though. Hope it makes it to Harewood!

[Hisnibs 10]

Pretty sure that mesh is meant to be there matey - believe it reduces oil loss into the intake via the pcv. I've certainly got one.

[oxfordpaul 0]

I've just found a diagram and it's described as a flame trap coil? Looks like a spring on the diagram, not all squashed in like mine, so maybe it should be on the outside within the rubber hose but has been pushed in by mistake. If anyone else can comment would appreciate.

[Hisnibs 10]

Oil loss/flame trap. It's meant to be there. Leave it alone or at the very most check its condition by lifting the lid.

[seanl82 23]

Sorry bud, others are right. At first glance it looked like a mesh of wires from the unterminated part of loom you have. Sorry if it caused undue panic!