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Discussion Starter #1
I have a 2006 Focus ST just got the car and was aware that it had a high idle problem. I was told it needed a Idle air control valve and did some research and it seemed like that was the problem. I put a new IAC valve in but that didn't do anything. The symptoms are when I'm coming up to stop light/ sign I take it out of gear and am coasting my rpm's go up to almost 3 thow and seconds after I come to a stop they go back down to 1 ish. My high Idle also helps maintain my speed sometimes which I don't want most of the time. I do have a check engine light on, so got it scanned at oreilly's and the first code was fuel was to lean then 2nd code was cylinder #1 misfire. I'm thinking that is a vacuum leak somewhere but not sure if that's my high idle problem. Hopefully yall could shed some light on my problem I'm having
 

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Things that cause high idle

Vac leak
bad IACV
After market TB and idle screw adjusted wrong ( DO NOT TRY TO ADJUST THE SCREW )

A Vac leak would cause your high idle and the lean code you go so I would look for a Vac leak

Tom
 

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If duratec motor then the PCV hose can split to do that...................
 

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Discussion Starter #5
I replaced the pcv hose as the old 1 was cracked and collapsed and checked the pcv valve to make sure it was working. Put it together and ran great, then I went to get my CEL checked, and they were able to clear it. About 2 weeks after I replaced the pcv hose, my CEL came back on, got it checked and misfires' on multiple cyclinders occurred. No more high idle though. I have replaced plugs and inspected coils/rubber all good. I did put new o rings in the IM and torqued bolts down to spec all good. I am confused on this misfire problem, I have tried to listen for vac leaks and carb spray hoses but nothing I can find, bout to give up and bring to shop.
 

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Vince your Moderator
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Vac leak as Tom noted
 

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Need more details.

Single random misfire code or multiple codes for different cylinders?

Actual codes always help narrow things down, description of them can be misleading.

What kind of plugs? Check the gap? How many miles on it? Plug boots can go bad over time from what we've seen here, they aren't expensive to replace.

Not sure from the account if the plugs were replaced before or after the code appeared.
 

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Discussion Starter #8
3 codes. P0300: random misfire detected. P0302: cylinder 2 misfire detected. P0316: misfire occurred in first 1000 revolutions. I replaced the plugs after the second time my CEL turned on, they are bosch iridiums
 

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Vince your Moderator
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Have you swapped two of coils around to see if you get the same codes for cyl#2?
 

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Vince your Moderator
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Ok. Post results please.

It's cool to see another desert rat here.
 

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Discussion Starter #13
I switched them up. But I can't tell which one is misfiring, it tis a slight misfiring goin on, so hard to tell. I need like a stethoscope or something to listen closer to each cyclinder.
 

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Vince your Moderator
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Get the codes read again, if the code changes to a different cylinder, you know which coil is bad.
 

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Discussion Starter #15
Hey it was coil for cylinder #2 that was bad, and also the pcv valve was bad too(Main Problem), I replaced both with also a new pcv hose. Car runs like a champ. Ive also removed the ticking tumble flaps in the manifold, it did not affect performance, but it seems like my focus turned a little cold blooded. Until engine is warm, it starts right up. Thanks for the help
 

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Good job, thanks for the update on your solution.

Multiple factors make finding all loads of fun.
 
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