Ive got a 1.6 golf driver 1989 173k miles. original pierburg carb and engine ect. recently changed the plugs and leads, cleaned my rotary arm and contancts...
at cold it revs up fine on choke , after 10 seconds it will missfire to the point that im needed the accelerator to keep it running, after approx 40 seconds i can let it idle its self and the misfire goes. now if i drive it straight to work, after 5-10mins of steady driving it starts to miss again and the only way to clear it is pull up and idle.
the problem does not occur if i fully let the car warm up idling and then drive it.
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dolly
It might be wise to check the hot-air pick-up system; this could just be a case of carburettor icing. Quite a common thing on carb VW's if the temp is above freezing.
There is also a wax-pellet thermostat device fitted to these that can sometimes fail; it doesn't quite fit your symptoms exactly though.
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There is also a heater Hedge Hog in the bottom of the Inlet manifold that has a single wire going to it and an earth strap from the carb that needs to be checked. Measure the resistance of the heater and check the continuity to the battery Negative. Regards Peter
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ive had my intake apart this morning, first i dont think ive got enough vacuum to open the flap for the warm exhuast gas, if i open it with a screwdriver whilst it is running it will hold open, but it wont open without help. ive tried to get a good connection from the exhuast manifold to the intake, but i need a new connecting pipe.
ive blown the vacuum pipes to clear ne crap, and made sure they have no holes in. whats excatly provides the vacuum? on the inside of my intake behind the airfilter (where the 2 vacuum pipes go ) there is a brass cover, covering the 2 vacuum pipes.. how does this operate. also where is this heater hedgehog, is it easily accessable.
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I've found the original fabric coated rubber hose connections on the vacuum tubes become porous, leaking vacuum, Well worth while replacing ALL these connections (suggest one at a time to avoid confusion!) to ensure no vacuum loss.
Heater hedgehog is fitted into the base of the inlet manifold, visible if you remove the carb, but only accesible if you remove the manifold.(?) Single power feed should be visible running down bulkhead ?
Previous postings cover function of valve, will post separately if I can find it again!
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If you have a vacuum leak so there is not enough to open the flap of the hot air intake,this would also cause a weak mixture which could be causing the misfire.Check vac pipes and connections-inlet manifold and carb.
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As the misfire occurs almost immediately after start the culprit is the choke pull down unit. This pulls the choke open about..10 seconds after starting up until the auto choke mechanism starts opening the choke to prevent over choking. The device is a black plastic unit fitted adjacent to the choke with two small vac hoses going to it. You should see it described in the Haynes book, it is retained with a roll pin but requires the removal of the water housing from the choke.Check the condition of the vac hoses. the one that goes to the base of the carb has a tendency to harden and split.
Andrew
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Simplicate and add lightness!!
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where do the vacuum pipes going to it come from, is it the one next to the one that opens the exhuast gas flap? thats the first time someone has mentioned this, it definatly has the symptons of overchoking, would it be on choke all the time effectivly becuase this has failed?
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I think you are on the right track with the location of the vac hose, just cant picture it in my mind at the moment (Two weeks off and several bottles of Merlot!!). The choke will eventually come right off as normal, its just not getting that little bit of help it needs immediately after startup. The other faults posted will result in carb icing which is much more dramatic.
Andrew
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Simplicate and add lightness!!
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its MOT time thursday and saturday im working so its difficult at the minute. i am gonna sell the car as the insurance is steep for me being 19. but id like to see it go with the full MOT and problem free. im hoping its a simple case of the vacuum pipe has perished!
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