CAT Rattling after cleaning Speed Idle Valve, Mondeo

you dont say wot year mondeo it is but, has it got a 'sheild' under the cat thats loose and catching/knocking against the metal cat? this can be removed with force... if no shield then it must be inside the cat and a new cat is the only cure. good luck

Thanks for the speedy reply. No the cat is naked only a shield on exhaust manifold. I'm just well suspicious as it only manifest when releasing the throttle in neutral, and since I tinkered around for an idling problem it had.

Cheers anyway, probably go to the breakers and get on or get garage to take it off and try and remove foreign object. Thing is though when shaking it stationary and cold no rattle from cat, when engine running definitelt the cat has the noise.

thinking about it tho.. the cleaner that you used to clean the idle valve(im guessing brake cleaner or something )was the valve still connected to the engine or did you remove it completly and have it in your hand? the fliud used may have entered the cylinders and the very rich fuel like mixture may have damaged your bricks inside the cat.

Isn't there a heatshield further back on the passenger side just in front of the rear wheels?

I suppose that's feasible, I think it's too much of a co-incidence that it happened immediately after cleaning the valve, I remove it completley from the rear of the block cleaned it with petrol allowed it to dry overnight. As petrol is so volitile I assumed it had all evaporated although it still wiffed.

Also I thought the ECU module could auto balance mixture, but I guess only under 'normal' opertaing parameters that applys. Weird that you can only hear it when the engine speed drops when in neutral. I had to take the plenum off to get access I guess something could have fallen into the throttle valve but that's a long shot and it wouldn't be propagated throught the injectors. I'll test drive her tomorrow.

Cheers for the help. Would the cat, if it had loose bricks, make the noise when move when the engines off? because it doesn't!! ;-)

No just one cat connected near the downpipe and two silencers one at the back between rear wheels and you said.

Cheers Matt

silencer at the back but they are tight and snug and I'm 99% confident the rattle is originating from inside the cat.

Cheers

Yes there is above the silencer but they all seem snug and well fitted. The rattle is definitely originating from inside the cat, maybe I can just burn it off (foreign object) after a good run?

It almost sounds like it's sucking air back towards the manifold, as if it's coughing!! ;-) Dunno what that could. I guess it's just a *****ed cat ;-(

cut the top off, remove the bit, weld back together. I have done several, they last indefinitely.

mrcheerful

silencer at the back but they are tight and snug and I'm 99% confident the rattle is originating from inside the cat.

OK..just checking. THe one at the back came loose on my missuses car and it souded as if it was coming from the CAT area.

Cheers for the tip, I might well do that if it persists