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Graham3232

Misfire after belt change

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Hi Everyone,

 

First time here and I’m hoping someone can help me!

 

I’ve got a 2008 (old style) 1.4 petrol Fiesta, well maintained with 6K oil changes and the usual basic servicing which do myself.  It was running perfectly…  Then at 100K I took it to a reputable local garage for a timing and auxiliary belt change and also the water pump (which was ok, but worthwhile changing at the same time).

 

After I got it back I noticed a slight misfire at idle, just a small shudder every other second felt through the car.  I took it back and they did a scan (no codes) and test drive, said it was fine.  As it was due a service I replaced the plugs, leads coil pack, oil and filters and tried a fuel cleaner.  No difference. 

 

I lived with it for a few months as the car accelerated and drove fine as before.  Then when it went in for its MOT at 107K (different garage) I mentioned the misfire at idle which had not got any worse.  They said the HC emissions were 120 and they are usually about 30?  This suggested the engine was running lean and as the misfire occurred after the belt change the timing could be slightly out. 

 

They re-timed the engine (£100) and said it was the equivalent of half a tooth out on the belt.  The misfire still exists up to about 1200rpm.  It may misfire above that but I can feel it and it accelerates fine.

 

Has anyone any thoughts?  Could it be a failing sensor or something disturbed while swapping the belts?

 

Thanks in advance.

Graham.

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I'd hope it hasn't done any serious damage whilst the timing has been out

 

@iantt Least I managed to time it when a garage clearly couldn't :p ) 

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if this engine is same as the focus 1.6 petrol in design, which I think it is, then the crankshaft belt pulley and the two camshaft pulleys are not keyed on the shafts. they have to be poitioned correctly and then done up tight without moving them at all. so it is easily possible for one or more to be out of place. It can't be too much out otherwise the valves would hit the pistons in a calamitous way. I have no idea if these being slightly out would cause a misfire. you could check it if you got the timing tools. you have to take the valve cover off to access the slots in ends of camshafts (at the clutch end of engine).

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11 hours ago, isetta said:

if this engine is same as the focus 1.6 petrol in design, which I think it is, then the crankshaft belt pulley and the two camshaft pulleys are not keyed on the shafts. they have to be poitioned correctly and then done up tight without moving them at all. so it is easily possible for one or more to be out of place. It can't be too much out otherwise the valves would hit the pistons in a calamitous way. I have no idea if these being slightly out would cause a misfire. you could check it if you got the timing tools. you have to take the valve cover off to access the slots in ends of camshafts (at the clutch end of engine).

He's already paid for the timing to be done again by a different garage, I'd hope two local garages wouldn't mess it up haha 

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