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Discussion Starter #1
I have a 2002 focus SPI with a very erratic/rough idle. It started out as a slight rough idle and has progressively gotten worse to the point where it doesn't want to idle at all. It drives great with no noticeable performance issues it just won't idle. I looked the engine over and over for vacuum leaks but couldn't find any. Checked the EGR valve. Checked the IAC valve. I replaced the plugs and wires. I also replaced the upstream o2 sensor which didn't fix the problem. The thing is when I was replacing the o2 sensor I noticed the exhaust manifold has a decent size crack in it. Would this cause a rough idle issue? I'm not even sure if the crack goes all of the way through the manifold. Car keeps throwing code P0171 bank one system too lean. Would this crack in the manifold cause a lean running condition? Any thoughts or input is much appreciated.
 

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Could the crack cause the code? It is a possibility, where exactly is the crack in the manifold at? May want to take a close listen to each injector to make sure they are opening and closing without a hiccup. If you got the extra bucks go ahead and replace the manifold with a quality aftermarket or Ford piece. If you are a little strapped for cash run down to the parts store and pick up some JB Weld, fill the crack and let it cure properly. Normally I don't suggest rigging things in this way but I know not everyone has a bunch of money laying around all the time to fix things properly. Start the car and run it through the proper driving cycle, no check engine light and you are good. Most of the time cracks in manifolds tend to throw the 420 code. Hope some of this helps you out.
 

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The crack is right before the o2 sensor. I was thinking jb weld as a temporary fix and if that helped replace the manifold. I'll give the injectors a listen and see what I find out. I was thinking about replacing the fuel filter also. Might not fix the problem but it hasn't been changed in a while and they're pretty cheap anyway so might as well do it.
 
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