Engine Knocking

Post by **Bogwoppit** » 12 Jul 2008, 17:13

Well, I THINK it's just the normal movement, but just thought I would check. On tickover, when she's coldish, the engine judders quite a bit, and it sounds a bit like something's knocking from inside (thought it was the exhaust for a while, that sort of noise). It doesn't sound so bad when you're standing at the back though. Is the tickover too low? Or do they all sound like that? It doesn't stop or anything so I was inclined to leave well alone. As I say, just thought I would check.

Post by **kevtherev** » 12 Jul 2008, 18:28

do you 'set' the choke before starting when cold?

Post by **T'Onion** » 12 Jul 2008, 18:31

is it fine when its hot ?

Post by **VWCamperfan** » 12 Jul 2008, 19:29

If its misfiring when cold you tend to get a knocking from that cylinder. Would also account for the juddering.
Check choke settings and HT leads.

Post by **Bogwoppit** » 12 Jul 2008, 21:32

Erm... I don't do anything to the choke when I start it - just give it some revs as it starts otherwise it dies - ie. it doesn't start without your foot on the pedal like some automatic choke cars have to. The choke DOES work, and when I flick the pedal it goes off. Sometimes going down the road at first it feels as though it might be missing a bit, or as though it's not getting enough petrol... a bit sluggish, but I don't think it's a cylinder. Could be, but wouldn't that do the same all the time though? When it's hot sometimes it still does the knocking thing, but other times it's smooth as anything. I have just changed the plugs so I shall see what it's like now. If it still does it should I change the HT leads does anyone think?

When I took the old plugs out (which are actually only about two months old) they were quite black on the ends, although they did have the powdery greyish stuff there too...

Post by **HarryMann** » 12 Jul 2008, 23:01

Its idling a bit slow and that metallic sound you can hear is the spigot shaft rattling in the spigot bearing (needle)... bet if you push the clutch in it stops

Post by **Mr Bean** » 12 Jul 2008, 23:26

HarryMann wrote:Its idling a bit slow and that metallic sound you can hear is the spigot shaft rattling in the lpigot bearing (needle)... bet if you push the clutch in it stops

If it doesn't stop as suggesed above you may find the rear engine mount rubbers shot so the metal parts knock as the engine oscillates at tickover. This happened to mine and a set of engine mounts (2 + 2) from JK I think did the trick. No danger of loosing the engine as the mounts are designed to capture the engine even if all the rubber disappeared.

Post by **Bogwoppit** » 14 Jul 2008, 17:50

Oh that's great. Thanks guys, I'll try the clutch thing tomorrow, and if not I'll look at the engine mounts.

I thought it might be not getting enough petrol... hence the knocking when cold, ie, the choke not working or going off too quick, as when I first go down the road in it it's like it's not getting enough petrol, almost like the handbrake's on...

Not missing, just... that really!

Post by **kevtherev** » 14 Jul 2008, 18:06

Bogwoppit wrote: the choke not working or going off too quick, as when I first go down the road in it it's like it's not getting enough petrol, almost like the handbrake's on... Not missing, just... that really!

some more thoughts from me

there are three settings for the choke
the choke is set by fully depressing and releasing the accn pedal once before turning the key
it should start without any pedal pressing as it also sets the throttle to open

you could check the choke return spring is not broken.
that the choke pulldown unit is functioning.
carb off for these jobs though
(haynes procedure)

also take off the pancake and check the choke is functioning when cold and then when hot

Post by **HarryMann** » 14 Jul 2008, 18:34

The engine shouldn't flail about on tickover, that needs sorting first, get it idling clean when warm...
With a rich mixture, (e.g. choke staying on too long etc) petrol engines idle lumpily, rhythmically, throbbingly (perm for what strikes you as a recognisable sympton)
When weak they 'hunt' which is a longer term rise and fall in revs (flaky idle) and then don't pick up well when revving.

Post by **Bogwoppit** » 16 Jul 2008, 10:14

Right!

I know what it is!

When the engine is idling on a low tickover (possibly too low but it doesn't stall or struggle to keep going...) the whole engine rocks in the bay, and the big fat rubber seal round the engine which joins the... dunno... plastic/metal bit? Front plate thingy?... to the chassis and runs all the way round is knackered. When I put it back on as best I could and held that front plate thing forward against the chassis it stopped.

So... can you get those seals anywhere? I'm going to try that to see if that stops it before I start messing with the tickover, because as I say it runs/idles ok and I'm being fuel economic!!

Also, and thanks Kev, I'm pretty sure the choke is working ok, as it starts fine when cold and goes off when I flick the throttle down as it should. I've changed the fuel filter before I try anything else for that, because it's run out of petrol quite a few times and when I looked at the filter it's really manky!

I'll see how she runs now and let you know!

Post by **T'Onion** » 16 Jul 2008, 22:07

it would have help if you had said it was air cooled

Post by **HarryMann** » 16 Jul 2008, 22:34

Good, at least you've found it, but your description did leave a bit to be desired

50 rpm too low won't make a gnat's cocks difference to economy, but if it is running rough and slappy sloppy, won't be very green and enviro friendly when you have to change a spigot bearing

Post by **Bogwoppit** » 17 Jul 2008, 12:35

T'Onion wrote: it would have help if you had said it was air cooled

READ THE SIG ONION BOY!!!

How can you tell how many RPM it's doing??

Post by **HarryMann** » 17 Jul 2008, 13:01

READ THE SIG ONION BOY!!!

He shouldn't have to decipher a codified signature, or read one at all...

Maybe you should read this?

Technical Questions checklist FAQ. SAY WHICH ENGINE YOU HAVE