My MK2 Digi has gone mental

[barry sprout]

Hey
Any thoughts?
My MK2 digi was running fine, but been parked up for 6 months.
Charged battery, fired her up - first time, nice idle, all good.
Left her to idle for a bit, then starts running rough, coughing, backfiring and cuts out with some smole coming from airbox.
Now she starts everytime but won't idle and cuts out unless I keep foot on gas a bit and keep revs up, but as she warms up it gets worse, much rougher, revs hunt up and down and she cuts out.
All rubber pipes good, nothing blocked. Blue sender is new. Replaced ISV and flying saucer with spare to no effect.
Now the only thing I CAN see is the bottom pipe to airbox from exhaust manifold is split and the thingy it connects to on the exhaust manifold seems to be loose/broken/falling off. I don't know what this jobby is, and I can't get to it to see as the throttle body/injectors are in the way. I've looked on my spare car (was a runner, now for spare parts) and the same thing has happened on that one. Both cars were running fine - so I'd have thought this situation would have been the same even when they were running...
Any thoughts greatly appreciated 

[rubjonny]

have a look at the timing, sounds to me like its slipped a tooth, check the tensioner hasnt siezed or something.

[barry sprout]

Aye
I was hoping to follow your digi tune up guide but the state of it at the moment means it won't run well enough.
Re the bottom tube from airbox to manifold, I guess this isn't really needed, so the fact that it's split shoudln't make any difference, I guess it's open ended anyway and just sucks warm air off the manifold?
Do I need to do anything to the airbox or set-up to allow for the fact that this pipe is now redundant and could that cause the terrible running problems?
I'll check the timing tensioner, thanks.
It's a well set up car , so I'm thinking the timing belt slipping is unlikely but could of course explain things.
It seems to be OK when first started, and just about idles, then gets quickly gets progressively worse as it warms up with the idle getting erreatic and car dying, worsening over the course of a few minutes to backfiring and smoke from airbox...
I'd have thought that the symptoms would be constant from fire-up if it were timing?

[barry sprout]

You may be onto something re the timing John... the timing belt is slack as a [insert favourite rude expression].
There is about 10mm play in the middle of the belt if I grab it and wiggle where it passes the alternator - too much I deem.
Any advice on easiest way to check and service the tensioner?
Cheers
Barry

[rubjonny]

ouchie thats not good at all
i'd just chuck on a new belt & tensioner for the price of them, unless you know its pretty new. in fact I happen to have a bosch belt and a febi tensioner just lying about I dont need!

As for the pipe you mention, no its not really a problem. its there to make the car warm up a wee bit quicker is all, for emmissions more than anything else!

[barry sprout]

Well it's an AGG 2.0l bottom end so I'd need a belt and tensioner to suit.
How does the tensioner work - I assume it adjusts automatically to keep correct tension?
If your bits will fit I may be interested if my tensioner requires replacement, how much?
Cheers

[rubjonny]

Ah, belt no good to you then! The tensioner would still fit but its less effort to just buy em as a pair from gsf or avs.

The tensioner isnt that clever, you simply rotate the middle of it clockwise till you can twist the belt 90degrees at its longest stretch.

To rotate the tensioner you can either spend money on the right tool (simply a handle with 2 pins on it!) Or save yasen some money:
1. fit a socket the correct size on the bolt
2. crack nut loose
3. put an allen key down one o the holes
4. push it against the socket & nip up nut when the correct tension is reached.
5. spin engine over a couple o times and recheck tension & timing marks, adjust if needed

[barry sprout]

You're  a star
Thank you
 

[barry sprout]

Last dumb question!
Setting the cam-sproket position:
Mine has a notch marked OT on the sprocket and a corresponding mark OT on the plate attached to the head.
Pulled spark plug 1, put piston to top of stroke and lined up the OT marks - it seemed to be OK.
The cambelt is too slack though.
So I take off the tensioner (which is not seized) and get the OT marks perfect and the piston top of stroke. In this position when I try to put the cambelt on the cam sprocket by manually tensioning the belt on it's upper run (ie the side of the belt that runs direct from the crank pulley to cam sprocket) and try to slot it onto the cam sprocket the teeth of the belt match up with the teeth of the sprocket - so it'll only fit if the timing mark on the sprocket is out.
I assume:
1. that I'm refitting it the correct way (ie tension the upper run of the belt by hand then tension the lower run with the belt tensioner).
2. The belt must be stretched and require replacement.
Sorry for being thick here (gotta learn sometime!)

[rubjonny]

watching the piston isnt the best way to get tdc accuratly on the bottom end due to the dwell angle, best way is to use the punch mark on the flywheel!  to see it you need to take out the green cap on top o the bell housin, but ya wanna do that anyway to you can check the ignition timing.  There is a crank pulley mark & arrow which will also work, not quite as accurate as the fly marks but should be close enough.

What I do is set the bottom end to tdc, then line up the cam sproket just before tdc & fit the belt. then i turn the the cam anti clockwise  till the belt tension is just about right, then do up the tensioner. spin it 360 degrees, re-check marks & tension.

I'd be putting a new belt + tensioner on there even if you suspect it may be stretched!

edit: here are the tdc (punch) and btdc ign timing marks (big arrow)