Ignition timing slipping + other issues!

[napoleonsolo]

Hi people,

Having a most frustrating time with my 1990 1.6 Mk2 Golf.
My latest problems are the ignition timing slipping about 20 degrees either way over 10-15 miles. Obviously this is causing all kinds of problems.

I thought the crank sprocket key might have sheared, causing timing to drift as the pulley wobbles horifically, but it hasn't.. The crankshaft nose is fine as are the sprocket and pulley so i feel the wobble must be caused by the crank itself- could it be bent?

But anyway, the timing.. If it isn't the static timing slipping and the distributor isn't moving (which it isn't) then what could be causing this?
Some other issue with the dizzy? It's a new Bosch style no name one from GSF.

Any ideas would be welcome.. I'm nearing the end of my tether with this car!

[ChasR]

How is the distributor driven off the crankshaft? Is it a genuine Bosch distributor?

Surely it's not a pleasant driving experience if it is so variable in timing.

[RobinJI]

A 1.6 mk2 will have the distributor driven off the auxiliary shaft.

Have you checked that the vacuum advance is intact and in place? Otherwise I can't see what would cause this unless you've got a dodgy distributor through bad luck. Is this the reason you changed the distributor, or has is started since?

The other than the distributor or vacuum advance, the only thing I can think it could be would be if the key-way in the pulley wheel for the auxiliary shaft was warn massively, but I'm not sure how that could happen.

[jrevillug]

IIRC, the dizzy on these is driven from the cambelt via a layshaft.

If the engine's performance is varying with the timing - as you'd expect - then the timing is indeed out. This could be caused by either the cambelt pulley being loose on the crank, or the layshaft pulley being loose on the shaft, a sticky advance mechanism in the dizzy, or loose layshaft-to-dizzy gears. There are no other points of play.

Of course, if it's the crank pulley, then the camshaft timing will also be all over the place, which will only amplify the effects of the incorrect timing.

I trust that the crankshaft pulley is done up properly (FT, possibly EFT).

Bear in mind that the static timing is just the relationship between the spark and the piston movment. If the crank pulley is loose and the timing marks are floating about - but it's running properly - then the timing itself is fine.

[napoleonsolo]

It is indeed driven off the aux shaft. And it's not pleasant to drive no!

The vacuum advance seems ok (can't suck air through it) I changed the distributor because i had ignition problems and the one on there was in bad shape and missing parts.. I don't know if this was happening before as i hadn't been driving much..

Not sure about the keyway although i also can't imagine that happening.

I'm stumped.. I think it has to be the dizzy.. Maybe the hall sender, i don't know. Or maybe the vacuum advance is sticking on somehow.. I did have misgivings about buying a non Bosch one but money is tight....

[napoleonsolo]

Ok just to clarify- I'm sure the static timing is ok- All the marks (flywheel, crankshaft intermediate shaft and camshaft) pulley marks line up.
If there was a problem there they would be out..

The pulley is done up properly, although i don't know what FT and EFT means?

Is there a way to check whether the vac advance is sticking?

Thanks for the help

[welshpug]

fecking toight, and extra fecking toight

[MrSpeedy]

Apr 18, 2012 18:28:00 GMT napoleonsolo said:

Is there a way to check whether the vac advance is sticking?

If it's the same as the older stuff ( I can't remember tbh cos it's been a while since I've been near anything so modern ) But you should be able to take off the dizzy cap, remove the manifold end of the vacuum advance pipe and suck like a Las Vegas hooker. You should see the mounting plate in the dizzy move slightly if the vacuum advance mechanism is ok

[jrevillug]

Apr 18, 2012 18:32:16 GMT welshpug said:

fecking toight, and extra fecking toight

Yup - sorry, should have been clearer.

Apr 18, 2012 19:04:18 GMT MrSpeedy said:

If it's the same as the older stuff ( I can't remember tbh cos it's been a while since I've been near anything so modern ) But you should be able to take off the dizzy cap, remove the manifold end of the vacuum advance pipe and suck like a Las Vegas hooker. You should see the mounting plate in the dizzy move slightly if the vacuum advance mechanism is ok

And yup also. Although the baseplate is often hidden beneath covers and rotors in electronic dizzies.

BTW: Static timing is ususally used to refer to the static ignition timing: the relationship between the spark and the piston when the engine's not turning. Compare with dynamic timing, which is where it's running. The relationship between camshaft and crankshaft is the camshaft timing.

I take it that you're using a timing light? If so, it's worth checking that the mechanical advance in the dizzy isn't sticky - try revving the engine while watching the timing mark on the pulley with the light. It should swing away from the stationary timing mark as the revs increase.

If the crankshaft timing belt pulley is moving back and forth w.r.t. the crankchaft (can't see how it can, but if it is) then both the camshaft and ignition timing will vary.

[ChasR]

All good advice .
To rule the vacuum advance block the vacuum port on the manifold and see what happens to the timing.

[carat 3.6]

Apr 18, 2012 18:32:16 GMT welshpug said:

fecking toight, and extra fecking toight

Quote of the day.

[napoleonsolo]

Right thanks folks.. In that case its EFT! The mechanical advance seems ok- it does swing away from the pointer.. I will check the vacuum advance.. If i block the vacuum port on the manifold, what should happen to the timing?

Also what do people think about the possibility of a bent crankshaft? I thought it seemed unlikely but spoke to a vw guy who said he'd seen it happen to a mk2 GTD..

Thanks again, much appreciated

[MrSpeedy]

A bent crankshaft is both unlikely and irrellevent to ignition timing issues

[daverapid]

Rotor arm keyway worn? Had it on Skodas.

[napoleonsolo]

Sorry, i realise it isn't relevant to the timing, it's just another thing i'm trying to get to the bottom of. I know it's unlikely but is it at all possible? Because i've replaced all the other components that could be causing the wobbling pulleys and still it persists!

It's defo not a worn rotor arm keyway- it's a brand new dizzy! I have found that disconnecting the vacuum advance does not cause the timing to retard as you would expect.. Also i can suck with all my might (ahem) on the advance capsule and cannot see the plate moving at all- I think this confirms the advance is sticking..

What i assume is happening is it is sticking at some point between fully open and fully closed and i set the timing. Then during driving it unsticks somewhat and alters itself.. I re-set the timing and the same thing happens.. Got a mates dizzy i can borrow so we'll see what happens.

Cheers for all the replys.