I was wondering whether anyone could point me in the right direction. I have a 2002 Ford Fiesta I cannot swear to it but I think it is a duratec petrol engine. It defo is not a Zetec. The car keeps stalling is difficult to start and lacks power. My first thought was an EGR valve but I may be being misled into thinking it does not have one. I plugged a diagnostics computer in and it came up with DTC codes P0303 and P0304 misfire on cyl three and four. The plugs leads and ignition pack have been replaced but the problem persists. Has anyone else had this issue and if so what caused it?? I have not checked vacuum pressure yet but this will be my next step.

The cause of the problem is the engine is mounted too close to the windscreen so the water runs off into the engine bay and into spark plug bays and causes problems but when this happened to my old car (04 fiesta flame 1.4) I had the plugs rt leads and the coil pack changed but heard some times can have doggy parts so may take a few goes to get it right again hope this helps

Ah thats interesting because the area around the the plugs is wet. Today I started it and it ran better although not perfectly. I think you may have something there. I presume when the car was hot on a long run the problem went away?

Update on car. The DTCs also include a random misfire. What has been done so far. Coil pack checked resistance within normal range. HT leads checked and fine. Plugs gapped correctly. Fuel filter replaced. Air filter checked. Compression checked and all cyclinder are within 10% with a reading of around 14 Bar. I have also sprayed WD40 over vacuum hoses and no change in idling. Last test completed with vacuum guage. The vacuum is low about 16 in Hg. The car has done 105,000 miles and checks reveal the cam belt has not been changed. I now suspect that the cam belt may have slipped a tooth leading to late valve timing. I am going to take belt covers off today to examine belt and NOT start the car again until the belt is replaced. If it is the case the compression figures would suggest I have been very lucky!!!!!

This would explain why the car is running like a pig. Can anybody confirm if my suspicions are correct?

Cam belt checked and fine. Cam sensor checked and resistance ok. Its looking like a zapped ECU

was a ford coil pack uesd as some aftermarket one are not up the job, did you change the cam belt as they can look 'fine' right up to the point that they snap.

Coil pack fine and cam belt fine. Regrettably I have discovered the cams lobes and hydraulic tappets are knackered. Hence the misfire. Only discovered this when I took off cover. I guess it explains the vacuum drop. I can only assume at some point recently some moron has used the wrong oil and as a result partially starved the top end of oil because I have never known this happen to a coorectly maintained Zetec engine. You have been warned. The car is not worth saving so I sold it to a trader for breaking. Best option. Still I made a wee bit of profit :)