I can disconnect the lead to no 1 cylinder and it makes no difference. Aha it's the lead, no there's a spark; so it's the plug, no that's ok too (swapped with another and no difference). Dizzy cap is new and when checked for cracks is ok; rotor arm is also new (and cleaned on the tyre sidewall just to be on the safe side). Electronic ignition has been fitted by the PO, make unknown. So is it fuel? No 1 plug is black but electrode is a mid brown colour. Carb set up is twin Weber 34 ICT on a 2 litre. Other plug/cylinder fuelled by this carb is ok. So my thinking is it isn't fuel related either. Specialist has suggested trying a fuel additive in case there is a blockage in the carb or a sticking valve which I'll try tomorrow. Before I do a compression test any sugestions for anything else to try? Thanks, Jeremy
Hi Dicky, because it sounds awful, especially when revved and it was popping on the overrun. I knew it was misfiring and wanted to know which cylinders were affected; turns out it's no 1 which is the culprit.
What colour is the spark? (blue or yellow?) Popping on overrun? exhaust or carb popping? Have you set the tappets?
Hi Paul, Blue spark, exhaust popping and no I hadn't thought about oradjusted the tappets. Are they a possible cause then? Thanks.
I'm with Razzyh, I would adjust the tappets on that side before anything else. Or a compression test if you have the "goodies" for it. I would think if it were carb.'s that whole side would be giving you grief. In other wards, if you did the same by taking the lead off the other and back on. BUT let us know.
Thanks for all the replies - really helpful. I'll adjust the tappets and see what happens then. I'd need to borrow the goodies to do a compression test in any case. I have taken the lead off the other cylinder on that side and it made a noticeable difference so whilst the carbs are still a suspect but lower down the pecking order. The specialist spent a while adjusting the carbs but did say the best way is to put the van on a rolling road.
As above, tappets are always a good starting point. No point in having a decent spark (is it a fat blue one) if there's little mixture getting in to ignite.
Weird I know but when I suffered the same problem a few years ago I tried the usual stuff like timing and tappets and plugs and it was gradually improving. No 3 cylinder seemed to be the weakest judged by the drop in revs as I took each lead off in turn. I finally cracked the problem by synchronising the carbs and the relief was immediate. It had had a new left hand carb fitted not long before I bought it, installed by a VW dealer in Spain according to my paperwork, and I guess after running it in it had never been readjusted.
These are new carbs installed by the PO. The receipt from VW Heritage is for 2011 but the carbs I'm told, have a 2009 stamping on them. The specialist attempted to adjust them yesterday but couldn't get a reading on his meter so suggested the fuel treatment in case there's a blockage somewhere. That is a distinct possibility as the van broke down on its way home after being bought. Cr#p from the fuel tank, the van had been standing unused for months maybe years, being the culprit. The carbs were stripped and cleaned and a new, larger fuel filter fitted but it well be that there is still some crud in the system which is causing the problem or it could be a combination of fuel/dirt, tappets and sticking valve - I think it's tappets first and move on from there! This weekend was supposed to be a waxoyling session for the underneath and door insides but it looks like rain so tappets aren't a bad way to spend the time instead! Anyone have a recommendation for an easy way to set them?
Tappets arent that difficult on a type 4. I set mine by spinning the motor using a spanner on the alternator, getting the rotor pointing at each cylinder in turn and setting inlet and xhaust to 0.15mm on the feelers. Might be useful at this point to see whether youve any movement on the rockers on that cylinder and if there are actually any gaps. so get it to tdc on that cylinder and give em a quick rattle - you get to know the noise they make when you rattle em and how that relates to the gap (whether its about right) as they will sound the same (ish). Just had a thought - what year is it? as later ones are hydraulic ie you dont set em up the same!
Thanks Dicky - the same thought had crossed my mind! It's a 75 and the M codes show it was originally a 1.8 but has had a 2.0 replacement engine, so I'll need to dig out the engine number and check what tappets it has. I think it was from 78 that hydraulic tappets were fitted? Thanks for the tip on using the alternator I'll give that a try and the measurements as well.
easiest way to tell the difference between hydro and non hydro is by the pushrods... steel for hydro, and aluminium for non hydro
Thanks Paul, this site is full of tips like that - or checking if your engine is cooled sufficently by touching the dipstick after a good run, warm ok, hot need to worry!
