Hi, I have recently bought a Fiesta Zetec 2004 1.4 petrol.

When I got it, the engine was misfiring going up any hill in higher gears(gear 3,4)or when changing gears a little sooner. What the car was doing, was a pinging/knocking noise occupied with juddering and no acceleration at all. I am not too sure where the pinging is coming from, sometimes it sounds like left side of the front of the car, sometimes it sounds like the exhaust.

 I thought it would be the spark plugs, so went to local garage and had them replace the spark plugs. The old spark plugs were black and dry. They have changed it and the car was running fine with occasional pinging.

However after few weeks it started doing it more and more. Now, when idle the engine will shake a little sometimes, and does the same juddering and pinging noise with no acceleration when i am in low rpm and change to higher gear, or going up a hill.

Also, the fuel consumption doesn't seem right, as it has done around 140 miles on 3/4 of a tank.

Black spark plugs mean running rich... not enough air, so have a look at the air filter (both sides, not just the clean side...... 😁...) 

Thanks for your reply will change air filter tomorrow. I have just checked and the intake hose seems to be broken? The right hand side big intake hose that connects to the engine/engine cover box. It seems thay the clip broke and doesn't hold properly, could that be causing it

11 hours ago, Jaro1 said:

I have just checked and the intake hose seems to be broken? The right hand side big intake hose that connects to the engine/engine cover box. It seems thay the clip broke and doesn't hold properly, could that be causing it

They're all broken, it's a terrible design.  However, it won't make any difference to the engine even if you remove that pipe completely as it's pre-filter.

My guess would be coilpack for your current issue, does it get worse when warm?

3 minutes ago, TomsFocus said:

They're all broken, it's a terrible design.  However, it won't make any difference to the engine even if you remove that pipe completely as it's pre-filter.

My guess would be coilpack for your current issue, does it get worse when warm?

I think coil pack has been changed before I bought the car, seen it somewhere in service history- It dont make a difference whether the engine is warm or cold

Checked the car today an obd2  reader - Cylinder 3 misfire. I have replaced, plugs, coil pack and ht leads - it still misfires under 2k rpm, then its fine? The car does feel a bit swifter though. Also misfires when moving off from a hill 

What spark gap did the new plugs have? The manual says 1.3mm. I put new plug with 1.0mm in mine and it fixed the misfire on cylinder no 2. Your cylinder no 3 is the 3rd from the left looking at the engine when standing at the front of the car.