Hi,

This morning I noticed an odd hissing noise coming from the engine, and is more noticeable around the exhaust tailpipe, which gets louder when you rev it.

Along with this the engine feels really hesitant/sluggish and not as responsive as it was. Also when revved the engine seems to sound deeper (best way I can describe it).

I've checked all the plugs and cleaned them, all fine. Also given the cat converter a good tap to see if its disintegrated and blocking the exhaust, again all fine.

I replaced the rocker cover gasket on Thursday and am wondering whether a disturbed something when I took the air filter housing off, although nothing seems obviously wrong. When I took the rocker cover off there was a load of crap in there which I removed (don't know if this has done anything?)

Oh and it's a mk3 fiesta 1.1 and only done 30,000 miles. I serviced it last year (oil, oil filter, fuel filter, air filter).

I've run out of ideas now and I'm not driving it in case it gets worse or gives up.

Any help would be greatly appreciated.

might have knocked off/damaged a vacuum pipe, see if you can pin the hiss down to a specific area if you can hear it with engine ticking over.

a good way of doing this is a 2-3 ft length of small hose pipe, one end in your ear whilst moving the hose around the engine with other end, hiss will appear a lot louder when your close to it

Check around the inlet and exhaust manifolds, you may have caused a gap when moving parts and hoses.

Thanks for the help.

After poking round the engine with a length of pipe to try and hear the noise better I couldn't pin it down, I am now convinced it's the exhaust, not the engine.

There's smoke coming from it when revved and the hissing gets considerably louder at that end, after you let off the throtte the very loud hissing

remains for a moment then dies down.

I'm thinking maybe a blockage in exhaust somwhere, stopping gases escaping as quickly, then when they have got through it settles down

again. What do you think?

Oh and there is a slight blow the exhaust at the center silencer which needs fixing for the MOT - only a small one though. Don't know if it would matter just thought i woud add it.

could well be a blockage in exhaust, if it is you dont want to leave it too long to fix as the back pressure can damage both the cat and 02 sensors.

with the hiss being more audible at the rear, suggests the blockage is in the rear section, otherwise the hiss would be more audible at the centre silencer leak.

Yeah I'm not driving it until it's fixed.

Start investigating the exhaust now.

Just got back this afternoon and now it won't start at all. :(

Breakdown man has been called :(

UPDATE:

Mechanic said it was the cat that was blocked within 2 minutes of getting here, so I've decided to do the whole exhaust as the center needs doing anyway. Not going to the garage as it would probably cost more than the car is worth to have it done.

Ordered the parts, should be here by the end of the week :) Fit at the weekend :)

would take a lot more than 2 minutes to diagnose a blocked cat.

diagnose a blocked exhaust maybe, but not pin it down to cat...he maybe right though

Well we'll see, as I said the exhaust needs doing anyway so it's nothing lost if it isn't the cat.

a genuine cat isnt cheap but far better quality than aftermarket...if yours is original i wouldnt change it unless necessary if not replacing with a genuine one.

if you do, be aware that genuine cats are worth decent scrap money...averages around £50 round my way

Didn't know they were worth that much. Thanks:)

I was going to keep the old one for now as I wad going to see about having it reconditioned at a later date. Just want a quick fix for now without taking it in anywhere

I'll definitely keep the old one now. Thanks

I've dropped the exhaust, so whilst it's all off I had a go at starting it so I can be sure there isn't anything blocking it. It still won't start (so much for the mobile mechanic's diagnosis).

I've checked all hoses and tightened all the jubilee clips (all fine), took the fuel line off the side of the carb, switched ignition on (loads of fuel coming through). So fuel shouldn't be the problem.

The only thing is, when looking down from the top of the carb I cant actually see any fuel in it (should it be really obvious).

Any ideas before I have to take it in somewhere?

Right well I ran out of ideas so I thought I'd have another look at the plugs.

They were a bit black but nothing major, but I thought clean them anyway and give it the best chance. STARTED FIRST TIME :) :) :) :)

However what would cause the plugs to need cleaning after only 300 miles and they weren't even that dirty - could it be a weak spark???

Edited October 11, 201312 yr by L666JER

a blocked exhaust can cause that due to the back pressure...

a blocked exhaust can cause that due to the back pressure...

Oh right, that makes sense.

I'll fit the new exhaust and see how it goes.

Thanks.