my golf misfires at cold and idles rough, ive changed most the ignition side of things, and ive set up the carb..
i carried out a cylinder leakage test:
cylinder 1.. 8%
cylinder 2 ..8-9%
cylinder 3.. 30%
cylinder 4.. 35%
this is at cold. i accept one and 2 as the car has covered 173 000 miles and you are going to lose some compression through wear ect. cylinders 3&4 are excessive, and with air bein supplied ( through the spark plug hole, with valves closed )i can hear a hissing through the filler cap and dipstick, its also present down the exhuast from number 4. there is no bubbles in the coolent. so this leads me to believe its valve seal failure, as piston ring failure would result in alota blue smoke..
so heres the question does anyone have any experiance in cylinder head/valve seal replacement on this engine? or is it better to take it to a vw specialist, approx prices?
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A leak test is Ok but may not be the cause of you misfire the hissing in the exhaust is implyinfg a valve leak and these can be re-ground or if necessary re-cut and the valves refaced and lapped in. I've done many of these.
You have done a leak test but have you done a compression test and can we see the results both cold and then after the engine has been running for 10 Mins.
Your missing at cold could be as simple as the hedgehog heater that is mounted in the inlet manifold beneath the carb has gome open cct, lost it's earth return of the single supply wire has fractured. Check these thinks and come back to the forum. Regards Peter
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A cylinder leakage test is an excellent diagnostic test IMO, much more informative than a compression test.
When two adjacent cylinders leak, the first thing I think of is that the head gasket has failed in the narrow strip between the cylinders.
There may not be any coolant loss, because the gasket probably doesn't have any coolant to seal in this area.
The leakage down the exhaust could simply be that the adjacent cylinder has an exhaust valve open, so the air goes in through the plug hole of, say, number four, through the leaking gasket to number three, where the exhaust valve is open, and out down the exhaust pipe.
The sound via dipstick and filler may be simply normal leakage for an old engine - how does the sound via this route vary between cylinders?
Try listening at the adjacent plug holes - i.e. 3 when you pump air into 4, and vica-versa.
Number_Cruncher
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Hi Number Cruncher, for clarity I was not knocking the leak test I was merely pointing out it may not be the cause of the mis fire. I agree about about listening to adjacent cylinders, I use a length of windsceen washer clear plastic pipe in side the un pressured pot to listen in. Yes you are right the golf engine does not have water at the narrowest point of the gasket. I would expect a failure here thou to not just effect the car when cold. Regards Peter
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just to confirm about the misfire at cold.. the engine revs up fine, oaccasionaly with abit of right foot but not always.... after about 5-10 seconds of reving it self at 1800rpm as normal it misfires i have to give a little rite foot to keep it running.
after approx 40 seconds - 1 minute it stops and will rev its self normaly. but as im sitting idling its apparant not all the cylinders r firing evenly, this is apparent even at full operating temperature.
ive got 2 options, have a bash at removing the head, and re-seating the valves whilst also replacing valve seals and gaskets... but risk fuking it up...
or i could take it to a vw specialist or a cylinder head specialist for them to remove the head and carry out the work. but im not planning on spending alot on the car as i approx its value at only £500
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but im not planning on spending alot on the car as i approx its value at only £500
Less. And in its current state worthless (except to you of course)
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the cars body work is immaculate, ive replaces all brake pipes and hoses, replace both rear bushes, replaced a rear shocker and a rear shocker top mount, both front control arms, 4 brand new tyres, front discs and pads.. (rear shoes r fairly new i belive) majour service inculding both belts, plugs , Leads, oil fuel filter.. ive cleaned and set the carb up and the gearbox is mint....all of that in the last 2months( the interior is also mint for age)
its only this misfire and cylinder leakage, and i no its had no majour engine work in 173 000 mile.. so its expected.
but i still no its old and £500 is a bargin to anyone, but i dont wanna plan on spending more than another £100 sorting it really, and im assuming it costs alot more than £100 for a garage to do my cylinder head, and of course check for any other problem when its off
i could do it my self, as i have done all the other work but i dont wanna mess it up and not have a car over xmas.
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Hi Peter,
I think that the leakage on cylinders 3 and 4 warrants further investigation.
Perhaps there is more diagnosis that the OP might consider, to make sure which cylinders are missing, for example, and to repeat any leakage or compression tests both hot and cold, wet and dry.
I like your tip about using a length of washer pipe to listen for any leakage.
I agree with your question about whether the gasket would cause problems only when cold. I don't know for sure. The gaskets that I've seen fail between cylinders have all been fairly large holes that would cause missing at any temperature.
Number_Cruncher
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if i do it my self the plan would be replace all gaskets anyway, so i guess i got that covered? worst case is a warped or cracked head. im leanin towards valve seals.
i just gotta get some quotes for other people to do, and then depending on price i might have a crack at it my self ( im an apprentice mechanic ).. although ive replaced everything else on this car, i dont want to mess up engine timing ect, specialy this time of year i need a car
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its not overly hard to remove the head and regrind the valves, try gsf or ecp for the bits and have a go over the christmas break...plenty of webistes to offer help
theres www.clubgti.com forums , you dont have to own a gti to go on there
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To make sure it is valves and not rings do a comp.test,note results,put a few squirts of oil down plug hole and repeat test.If the result is higher you have blow by,as the oil temporarily seals the piston if the rings are not.
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To make sure it is valves and not rings do a comp.test,note results,put a few squirts of oil down plug hole and repeat test.If the result is higher you have blow by,as the oil temporarily seals the piston if the rings are not.
thanks for the advice, i would have a go this weekend but im working, so then its christmas eve.. i will see how i feel.
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