Hi
my 1.6 mk2 driver runs out of steam at 4000rpm, lke hitting a wall, I've replaced plugs and leads and have tested the ignition.
I ahve also checked the valve timing marks and the ignition timing and tuned the carb.
any ideas?
the other funny is that the engine runs better when the ignition is way advenced (ie the haynes says it should be 18 BTDC at 950rpm) but my car runs happiest at about 28 BTDC. I suspect it would run fine beyond this but haven't tried it, I've never heard the engine pink.
I would suspect retarded valve timing (I changed the belt when I bought the car) but I have checked this quite thoroughly
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How old is the car?
Does it have a catalyst? (Doubtful, I know..)
Sounds like a blocked exhaust system to me
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Was it ok before you changed the timing belt? my money is on the belt probably being one tooth out. Can you recheck valve timing?
pmh (was peter)
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Drew,
I agree with pmh. An engine that runs better with ignition timing seriously advanced almost always has a valve timing error. By over-advancing the ignition you are matching the spark to the valve timing, but it is still all out of synch with the piston position. Golf cam timing marks can be rather strange; on some engines the marks do not appear to line up at all, with the camwheel mark somewhere around 7.0 o'clock at TDC. If in doubt go back to basics and observe the actual cam lobes, making sure that No.4 exhaust is just closing and No.4 inlet is just opening (ie "valves rocking") with No.1 at TDC on compression.
Other possibilities are blocked exhaust, restricted fuel flow (weak pump, blocked filter, and Golfs are prone to corrosion inside tank blocking outlet pipe), or a secondary main jet blockage in carb.
Regards, Adam
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Adam,
Tank corrosion? Dont they use plastic tanks? I am 90% sure my 88 GTI has a plastic tank.
pmh (was peter)
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Don't know if engine went better before I did the belt as I did it early on. I have tried with two belt positions so far:
the valves were origianlly one tooth advanced from where they are now. A re-reading of Haynes showed I was supposed to line the sprocket mark with the valve cover rather than the top face of the cylinder head so I then retarded the valves one tooth and to be honest it made no difference to the engine performance. This indicated to me that there was a serious problem as moving cam timing by one tooth should make a major difference.
I have since stuck a protractor on the camshaft and physically measured the crank angle at which all 8 valves were at max open and fully closed. these angles correlate to the spec given in Haynes (as far as measurement errors allow).
Adam is right that there is another timing mark on the camshaft which is at about 7 o'clock at TDC but my engine has nothing to line this up with as it is an early engine (1988) with a different upper cam belt cover to later engines.
I am 80% happy with my cam timing. It could be wrong but I have set it up carefully.
If Adam is right (about cam timing being set to match ignition timing) then this would indicate that my cam timing is advanced??
Having tried this belt setting I am not convinced, could retarded cam timing be compensated by advanced ignition timing. ie I might try advancing the cam another tooth and see what happens.
I think fuel supply is OK, golfs do have a placcy tank but rust from the filler neck is a big problem on some cars, my car doesn't have this (and my fuel filter is clean and generally half full of petrol).
could be exhaust, I had a new one fitted when I bought the car so again it is difficult to tell, is there any easy (or difficult) way to test this. I've had the exhaust off before and its a big hassle. I'd rather move cam timing first
thanks guys
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Will it rev freely when it is in neutral ?
If the engine is that old, and it has a carb, I'd reckon you have fuel supply problems, perhaps a blockage on one of the jets. When the petrol demand becomes too high it starves.
The rest could all be red herrings.
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it will rev past 4000 with less load applied. In fact it will get to about 4500 in 5th (not that I do this often) and about 4700 in 4th. My question is more that it really struggles at high revs and is really not keen to get past 85mph.
not sure what this means but the manual says peak power at 5200rpm which leads me to beieve that the car should have more go at this speed (plus my 1100 fiesta is faster)
the carb is high on my list of culprits, I had it apart last month and cleaned the jets, fuel pipes and float chamber. I don't think teh carb is the problem as this made no difference.
2nd stage throttle might be at fault but I have tested the vacuum operation (by sucking on the pipe) and that works, difficult to test whilst stationary as the loading cannot be replicated
cheers
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Does the timing advance automatically when you rev the engine (check using a strobe light on it)? I was trying to set the timing on my Visa and couldn't make head nor tail of it. I eventually decided that the auto advance was not working, and on stripping the dizzy down found that it was jammed on full advance, and had previously been set 'correctly' at idle, so it was much too far retarded at high engine speed. 28°BTDC sounds about right for full advance.
RichardW
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thanks, yes the mech and vac advances seem to work in as far as I have tested them. I also put a different dizzy (2nd hand) on with no difference.
28 BTDC is what it runs best at at 1000rpm. ie I have set it there myself beause that is what the engine 'wants' to do. it is around 40 BTDC at 2000rpm
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As this is a carb model it might have the rev limiting type of rotor arm which if old/worn can cut off too early. This was a common problem on old VW Polos/Golfs and some old Fiats.
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John, this sounds promising, tell me more. How would I tell if I have a rev limiting rotor arm? My rotor arm is a single solid piece of plactic, not sure how it would limit revs.
many thanks
Drew
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