Okay 400 miles into a road trip. Around 100 miles per day and it has started misfiring and backfiring/jolting when you first start up and run. Does it randomly until you have done 7 - 10 miles so I assume when it has warmed up. Before I check the plugs, rotor arm or coil any ideas? It is an electronic ignition so not points. Before the trip I changed plugs, leads, rotor arm, fuel pump, fitted a malpassi fuel regulator. Did valve clearances, timing etc etc. As I said ran beautifully for 400 miles!
It really doesnt matter whose electronic ignition you have , the days of it being an improvement seem to be over for some people. However its well worth checking simple things like the big black switched ignition wire is actually properly on the coil, that the plug leads are all in properly, that the distributor cap is clean and dry. It could be the shaking and jolting causes arcs which finally weld up and it runs OK. Also do your headlights flicker at the same time - it could be an ignition switch on the way out ..
I’m sure it is unrelated but my full beam blue light on my dash has stopped working. I’ve changed the coil but on a site so can’t try until tomorrow morning. Strangely the coil wire (powerspark HT leads) don’t fit as snug on the new VW Audi coil as they did on the Lucas one I have taken off. Hopefully it will start in the morning and run without issues. What I don’t understand is why it ran for 400 miles with no problems.
I'll go for partially blocked jet because when they are cold they want more petrol, when warm they need less. You ought to find out because you could be running permanently lean which is not good. In the meantime try not to put your foot down or drive to fast which it when a lean mix could damage the engine.
Unfortunately, I’ve done some big hills today coming out of Wales to Salisbury so have put my foot down a fair bit, but it seemed to cope well, when warm that is. Fingers crossed it hasn’t damaged anything. I had read somewhere that with E10 you need larger jets but I’ve been using E5 so it shouldn’t be that.
I don't want to be alarmist, but most people with an air leak which also causes a weak mixture report their bus was going really well before it went pop. What carb(s)? checking jets for blockage is normally quite easy.
Hi can I ask how do you check for blocked jets? Is it pretty easy as In can you see a blocked jet? Thanks Sent from my iPhone using Tapatalk
It is an empi 34 pict 4. As Andy says how do you check and clear blocked jets? I don’t have a carb cleaning set with me.
So really bizarre after changing the coil it started on the button but wouldn’t idle. Anyway set off thinking it might just need to warm up but then realised it just cuts out at junctions and lights. No backfire or misfiring though. So I’ve pulled into a cafe car park and changed the coil back (after fiddling with mixture and idle screws with no joy) and hey presto it idles. Just having a bacon butty and then will get back on the road fingers crossed it won’t misfire.
Rule of thumb - elec ignition modules and coils get worse as it warms up, they never get better. If you do have a partially blocked idle jet it will run better when the choke resets itself while you're messing about changing coils. The idle jet is on the RHS of the carb, it unscrews easily - google for a diagram. You may spot something like a slither of hose stuck in it. Just blow at it with your mouth, wd40, butane lighter refil, carb cleaner, brake cleaner - whatever you have. Of course now you have messed up the carb adjustment (I have no clue why you would do that, carbs don't unadjust themselves) you'll have to set it properly when you do find the real problen. Costs nothing to try. It's just advice, take it or leave it.
Ha ha, I like to make life hard for myself. Luckily made a note of the screw turns and just put back to where I started. My thinking was to try and make the mixture richer, I have these bright ideas sometimes. Didn’t seem to affect it luckily. Ok will take a look at that. It did pop and judder when I got going again and really slowed at one point like it was being starved of fuel so tending to agree there is a fuel blockage somewhere.
Okay which is the idle jet? I’m looking at the right hand side when facing the engine. Just tried to buy some carb cleaner from a VW Aircooled garage who had no interest in selling me any. Did get a tip from the mechanic though of putting my hand over the air filter high revs to blow it out.
The big one is the idle jet, you'll see three holes in the outside - favourite place for a minor blockage. AKA an Italian tune up. Use a bit of card or it'll make you jump!
Cleaned the jet with a flash wipe and WD40 (all I had). Starts and idles, we are taking it for a decent run tomorrow so that will be the test. Thanks for the tip.
Unfortunately, the saga continues and it is getting worse. Bought some brake cleaner from Halfords, apparently carb cleaner and a carb cleaning set is too specialised for them. Anyway whilst it did give a momentary break it continues to misfire until it gets hot so back to the campsite to see what else it could be. Firstly I checked the fuel pressure and couldn’t get it up to 3psi no matter how much I adjusted the malpassi, so I took it off. Once off I looked into the fitting that you put the gauge in and noticed a white mush of PTF tape. I’m thinking this is what is restricting fuel flow and causing misfiring. Anyway that is removed and fuel is direct from the pump to the carb so I’m going to have lunch and then give it another test drive hoping that none of that PTF tape made it to the carburettor or if did it has disintegrated now.
That hasn’t sorted it still misfiring until it gets hot, problem is it is taking longer into a run to resolve itself. Going to change the coil again, using a different HT lead to the cap and check the spark plugs. Any other ideas? I don’t have a spare dizzy or electronic ignition/points unfortunately.
