106 GTi knock

[James93]

Under load my 106 is making a loud knocking/banging sound which seems to increase with RPM, exhaust note sounds like it's choppy too, dip the clutch Rev there's no rattle/knock at all and exhaust note returns to normal, come off the clutch back into gear it knocks again.

The manifold is cracked but I don't think this is causing it, sounds like something metal is going bang bang bang, the gearbox side aeems to be moving quite a lot when revving the car, could thi be the issue?

[stevo67]

Check the upper & rear gearbox mounts.

[James93]

Rear mount is power flex, about a year old - engine is moving a lot, car sounds misfiring too and really down on power now, constant knock when accelerator is pressed under load, fine on idle/coasting an no knock when in neutral... Annoying!

[James93]

Couple of videos

https://youtu.be/r4yzsLVHuYQ

https://youtu.be/TTWaJ89wr5k

[welshpug]

that sounds like the bottom end is knocking its tits off.

[James93]

Exactly what I thought bottom end or rod knock. However rev it in neutral no noise at all.. Really strange I'd of thought bottom end would knock regardless

[James93]

The manifold has a nice big crack around the weld I n it also. Wouldn't cause this though no?

[Chipwizards]

Is it noisy in neutral with the clutch out?
Is it noisy coasting?
Is it noisy on overrun?

[James93]

No noise in neutral

No noise on overrun

No noise coasting

Only when throttle is pressed in gear. However does sound like it is misfiring now sounds choppy instead of smooth on idle it sounds like dududududud

[Chipwizards]

Broken crank maybe, I've seen them break before in such a manner as the front and back bits still engage and will transmit torque but there's a hellish rattle.

Take the plugs out and drop two 3/8" socket extensions down onto pistons 1 & 4 then get a friend to rock the crank back and forth and see if the pistons move exactly together by feeling the movement on the socket extensions. If the crank is broke there will be a delay in the movement of the one at the end of the crank opposite to the end being turned (so if you're turning the crank with the car in 5th gear and one wheel off the ground it will be the pulley end piston that is delayed, if you're turning the crank with a socket on the pulley it will be the flywheel end piston that is delayed.)

[James93]

My outer cv on drivers side has been split since August I completely forgot about it until getting under the car! Could this be the problem??? As its only when under load

[James93]

It's been making the noise for a while but it's slowly got worse

[James93]

And the misfire sound could be because the exhaust manifold is cracked around the weld where it goes 4 into 2 on the super sprint mani? Which I've not long discovered too ... Poxy car

I'm not entirely sure if the car is down on power just the noise is making me want to take it very easy indeed. Seems to occur more when warm, well it did now it's more frequent and certainly louder than the past few weeks

[BUMMERS]

You've got a load of known problems with the car and been given advice on how to check for something else.

Check the crank as chipwizards says. If that seems fine then start fixing those other problems.

Then see how it runs!

[James93]

I will check what was suggested I'm just throwing known faults into te mix incase they could be linked, as I know driveshafts knock when gone the noise tarted dull/quiet now it's got louder with a misfire, could be coincidence could be related

[Chipwizards]

It sounds to me like your car needs some proper maintenance generally.

[Synister]

Yeah a weekend spannering at it and doing a general service probably wouldn't do you any harm.

[James93]

I have everything here to resolve the issues however I've been working 7 days with no external lighting by the time I'm home it's dark so havent had chance, currently in NYC so can't get under the car til next week - yeah te car does need some work last time it was on track it took a bit of a beating unfortunately.

[holdawayt]

Strange that nobody has suggested the clutch.

If it's fine in neutral but struggles on load in gear you need to look at the part that is responsible for that change of state (clutch). I'd expect that the clutch has fallen apart or lost a spring and is clattering about.
They don't always have to slip to be faulty.

As said though, I'd take it off the road over winter and give it an overhaul. Sounds a right mess.

[James93]

Clutch wouldn't cause a misfire though, pedal feels no different but I will Inspect the clutch. Car is fine, it's a purpose built track car that I've built from scratch, it's rarely used. But is due for another track day in the next few weeks. Sure it needs a new CV boot but I have a replacement driveshaft for it, just haven't had time to get underneath as currently in New York and the car is at home

Exhaust manifold cracked is obviously due to manufacture defect which Is bein welded in the week, as its a super sprint Manifold, not a cheap ebay knock up