Car gurus please help

[89capricebass]

I bought a 2000 ford focus a couple of weeks ago. It has a 2.0L DOHC 4 cylinder in it. It sat in my garage for a couple of weeks until I could get insurance on it. I got insurance on it a couple days ago and started driving it. It ran fine for about 2 hours. I got it home to park it and noticed it was idleing rough. took it around the block and noticed that it would some times hesitate to go... sometimes it almost seemed like it was chugging along. The engine light came on so I took it to autozone and had the do a diagnostic check. They said I was having a cylinder 3 misfire. I checked to make sure the plug wires were in the right order and they are. I replaced the spark plug and plug wires, and gapped the plug to .050 like its sposed to be, but the problem is still there. Basically the question is what do you guys think the problem could be? I think it could possibly be an injector or maybe the coil pack? thanks ahead of time

[teardrop]

id go with coil pack first then injector

[captainhook426]

Check for a vacuum leak. I would almost suspect an intake with that motor. swap around your coil packs and see if the misfire moves, if no then it's not the coil pack. take a dmm and see what the resistance is of your injectors, the chances that just one of your injectors has failed is slim to none without there being other symptoms that you would've noticed first. other than that without real scan tool data I'm not going to try to point out everything else that may be wrong or that you could check for.

[CleanSierra]

Didn't autozone tell you what it could be after they diagnosed it for you? Injectors can't be that expensive for that engine. I'd try that and see if it works. Rough idleing i would've guessed mass air flow sensor first, but since they put the scanner on it, I guess that's not the problem. It doesn't have an aftermarket air intake on it does it?

[HatersGonnaHate]

Most likely a vacuum leak, egr valve or pcv valve malfunction. Cylinder 3 misfire could be brought up due to a bad knock sensor or a short in the spark plug boot. I used to break down the zetec engines daily, so I know a thing or two about it lol.

[crispy_chick3n]

could be as bad as a loss of compression on that cylinder. the newer focus 2.0 engines are nutorious for dropping valve seats, then all hell breaks loose. although i highly doubt you dropped a valve seat, because you would have noticed a lot more than just a rough idle. you would have noticed a very loud and annoying knocking. i would start with putting a spark tester on the number 3 plug wire and see if you get a spark. if you do you can rule out spark. next i would check fuel. get a stethascope and listen to each injector. you should hear a clicking sound from them. if you do you know the injectors are working. next check to make sure there is fuel getting to the engine. on the fuel rail if ford was nice there will be a schrader valve. push it in, it should spray fuel out. if it does you are getting fuel to the injectors, and you can rule out fuel. this leaves us with 2 possible options, air delivery, or engine mechanical problem. if you can find someone to run a compression and cylinder leakdown test on all 4 cylinders have them do so. you want to be within 10% of specs either way on the compression test. as for the leakdown i dont like to see more than 15% leakage on a cylinder. if you have low compression, or high leakage that would indicate either a burned valve, worn piston rings, or a blown head gasket.

if you take the advice givin here and follow the steps, you will find the cause of this misfire, and be a happy camper again. best of luck to you

Edited August 23, 2011 by crispy_chick3n