[pdxRR]

My 96 4.6 is making a clunking sound sometimes when i fire it up on a warm start.Is this a common problem? Can someone point me towards some possible causes?

It does this only at idle speed. It runs and drives fine otherwise. If i rev the engine the clunking sound goes away. No faults on the screen.

Thanks

 

[RRToadHall]

Re: Ever have this problem? Rough idle knocking sound warm start

It is definately not common or normal. How many miles have you done? Service intervals?

 

[pdxRR]

Re: Ever have this problem? Rough idle knocking sound warm start

About 130k, I've had it since 100k, full service history when i bought it. Since i've had it I've tended to staying on top of problems when they arise. Could it be an idle control valve, temperature sender? What about cam shaft position sensor? My knowledge is limited despite countless hours on rr.net. I just need some direction and i can go from there, was hoping it was common.

 

[viperover]

Re: Ever have this problem? Rough idle knocking sound warm start

I noted the word "sometimes"

could you clarify this as my response would be different if it were every time

 

[pdxRR]

Re: Ever have this problem? Rough idle knocking sound warm start

It happens when: I drive for 30 mins. Stop, shut off the car. Return within 5 mins, and start it up. Engine makes knocking noise for 30 sec. Under this scenario, it does it frequently, say 50% of the time. Otherwise i see no sign of it. Any thoughts?

Thanks again

 

[John W]

Re: Ever have this problem? Rough idle knocking sound warm start

Slightly different to yours I know,but then who knows.Mine statrted making a light knock.tapping noise just after start up when cold for 20 secs or so.
Thought it was in the engine at first ,then the water pump seized.After replacing the waterpump the noise has gone completely. :think:

 

[Ferdinand]

Re: Ever have this problem? Rough idle knocking sound warm start

I've tried excately the same!!!! even when cold - still haven't had time or patience - or energy to deal with it.... if it works - don't fix it.....

Ferdinand..... Cars are like women.... lovely, expensive and will ruin your economy!

 

[V8pman]

Re: Ever have this problem? Rough idle knocking sound warm start

it might be your drive plate, i had a knocking noise when i got the car on idle and my drive plate was in bits.

 

[lrscott]

Re: Ever have this problem? Rough idle knocking sound warm start

I had a slight knock and engine tick. I replaced the oil with 5w-30 cause it was cold out. So far the oil has gotten really dark within just a month and the knocks and ticks just vanished. The thinner oil must be cleaning out some of the gunk... idk. But it worked for me. Although, now its leaking a lot more oil :think:

 

[viperover]

Re: Ever have this problem? Rough idle knocking sound warm start

Why didnt I suggest this...anyway its time to carry out a oil pressure test, when knocking and when ok ..IMPORTANT

 

[RPM]

Re: Ever have this problem? Rough idle knocking sound warm start

When my '96 4.6 is cold I get a loud banging noise coming from the front somewhere.

If I leave it to idle for 20-30 seconds it goes away, or if I rev it a bit it goes away too.
Funnily though it doesn't do it when its warm i.e. if I turnthe engine off then back on.

It it a metalic clonk sound and is in perfect time with the exhaust note of the V8!
it increases as I rev the engine thine dies as I take my foot off.....

I am also noticing an occasional slight miss as though the engine isn't breathing properly so I wondered if it might be manifold/exhaust issue!

Still not got to the bottom of it though.................

Just hope its not gearbox.

 

[argonaut]

Re: Ever have this problem? Rough idle knocking sound warm start

Did anyone find a cure/cause for this ? My 4.6 makes a mechanical knocking noise when starting cold and on idle - if I run it on LPG then it makes this noise at idle as on LPG the idle speed is lower anyway. The sound disappears if the revs are above around 800rpm. I've crawled underneath and had a look around whilst the engine was running but can't see any obvious cause. I thought perhaps exhaust might be banging against something or possibly a knackered engine mount but I can't see anything. According to the previous owner, the drive plate was renewed recently (few months ago). Any ideas?

 

[argonaut]

Re: Ever have this problem? Rough idle knocking sound warm start

Did anyone find a cure/cause for this ? My 4.6 makes a mechanical knocking noise when starting cold and on idle - if I run it on LPG then it makes this noise at idle as on LPG the idle speed is lower anyway. The sound disappears if the revs are above around 800rpm. I've crawled underneath and had a look around whilst the engine was running but can't see any obvious cause. I thought perhaps exhaust might be banging against something or possibly a knackered engine mount but I can't see anything. According to the previous owner, the drive plate was renewed recently (few months ago). Any ideas?

I made a short video in which you can hear the knock knock sound I was trying to describe: http://s193.photobucket.com/albums/z314 ... ock001.flv

cheers

 

[viperover]

Re: Ever have this problem? Rough idle knocking sound warm start

Had a listen but.......sounds more like a popping noise in other words like a back fire...

Could be wrong but you may just have the dreaded carboned up valve problem, if so thank your rlocal petrol station for selling junk petrol but oil also plays a big role hence my insistant advice on using a diesel oil only, it doesnt carbon up

You now need to carry out a compression test, best way is to remove all spark plugs and start on the left, this is the only way to determine compression is up

I've been through this on 5 V8s so far, no mine I had 2 busrt exhaust valve and the rest were well carboned up on the stem preventing the valve from closing, car still goes but you will find it low on power.

but then it could be wrong spark plugs too or even a duff coil

 

[Shadow Keeper]

Re: Ever have this problem? Rough idle knocking sound warm start

Could it possibly be the timing chain and adjuster knocking about?