type 25 2l misfire and back firing again

[norman]

hi i am new to these forums and i am looking for help with my engine , it was running sweet enough but had the occasional backfire when coming off the gas , but the other day i started it up from cold and left it running for about fifteen minutes whilst being called away, however when i returned it was running like an old tractor , i havnt driven it since and i tried to start it yesterday and it still runs the same , i have had the same sort of trouble before and jk suggested it was the electronic ignition distributor causing the problem so i had a component replaced and it ran fine now i dont know, perhaps somebody could help :

[VWCamperfan]

If you left it I would imagine the choke was fully closed causing it to run on a too rich mixture. You must blip the throttle to reset the choke once it has warmed up and it should run fine afterwards.

[HarryMann]

,, and never a good idea to leave an engine idling, or at least an old one without full digital engine control. Poor lubrication, uneven idle, cold, condensation, lots of wear. Engines should be started and driven, 2,000 rpm for warmup , esp. if OHC
I expect it was just flooded and needed clearing out

[norman]

hi thanks for replying , the part that i had fitted to the distributor was a hall sender unit ,i didnt mention that i have twin webers als instead of the solex, is it the plugs that i have to clean or the carbs or both wwhat could have occured to make it misfire so bad now

[HarryMann]

Has it ever run perfectly on the Webers?
Backfiring on the overrun is indication of weakness on the idle jets.

Also, 'running like an old tractor' is not exactly a very technical or useful description.
What actually is wrong with its running - explcitly? Rev-bands, throttle positions and responses...

If you're running non std. carbs, maybe the whole thing needs setting up properly by someone who knows the weber/2.0 a/c setup well?

Put your location in your profile and someone might be able to advise where...

[norman]

thanks harry , sorry what i meant by sounding like an old tractor was that it does not sound like it is running on all cylinders , i thought perhaps an exhaust valve had burnt out , my location is near rye east sussex, It was running nice and smooth but leaving it to idle for 10 mins or so it just started to run rough, It has done a similar thing before but when starting from cold then as it warmed up it smoothed out. but this time it started smooth ,

[HarryMann]

OK, No.1

Take all 4 compressions, cold & then hot (yes, a pain, but if you know these then you have a known starting point (and you then know if you're wasting your time elsewhere)

[norman]

thanks harry
is it possible to get these compression tests done on my drive or will it have to be towed to a garage as it would be unlikely that i could drive it,
that does sound like good advice, thanks

[HarryMann]

Yes, on drive, pop the plugs out, borrow a compression tester, read the Wiki on compression testing (requires a reasonable battery charge) - or get a mobile mech to do it. Not difficult, want to be consistenmt and thorough those

[bennwedge]

Hello chris , welcome to the club. When I come round this week we can do a compression test together. I pulled this from the wiki earlier
Compression pressures - Bar (psi)
Engine. Min Typical Max diff
Air Cooled 2.0 5 (73) 6 (87) ~ 9 (131) 3 (44)

also after looking at the pics that I took today of your engine I've noticed a couple of problems on your engine that affect the cooling of your 3rd and 4th cylinders that needs sorting . Ben

[norman]

thats interesting , i appreciate all of your help