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2007 focus duratec stumbling

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the car is stumbling at both accelaration and cruising at all speeds. and will stall at idle.

I unplugged the MAF and it runs 100% fine but you can tell its running rich and has a slight gas smell from the exhaust. (This is how I'm driving it now to work)

Changed the MAF and cleaned the trottle and it no longer stalls at idle but I still have stumbling at all speeds as soon as the engine warms up. Which is normally just a few miles down the road.

No check engine light (well except when I'm running with the MAF unplugged), it is running a Cold air intake so I did check for loose clamps and leaks in the intake when I had it out to replace the MAF and everything seems nice and tight.

I did do a search on the forum and seen alot of guys talking about the PVC and fuel pump that that didn't really explain to me why it runs 100% perfect with sensors unplugged for me to want to yank the entire intake manifold off. Any thoughts from you guys would be GREAT!!
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FocusKnot

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2004 Focus Wagon, Zetec DOHC, Auto
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1,717 Posts
#2 ·
The rear PCV hose is a common problem on the Zetec for stumbling at idle....you don't have to pull the intake to replace that. For stumbling at all speeds, it is common for the ignition coil to have cracks that result in misfire. Also, the 3-wire connector to the coil can develop wiring problems right at the connector.
 
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Discussion Starter · #3 ·
Any way to test the ignition coils or am I just looking for physical cracks.

...Still don't understand how it would be ignition or plugs if its runs fine with MAF unplugged. Sounded more like a sensor issue but I'm open to check anything car has 240,000 miles on it.
 
FocusKnot

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2004 Focus Wagon, Zetec DOHC, Auto
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1,717 Posts
#4 ·
I'm just giving you a couple of things to look at...they may be fine.

The coil will have physical cracks on it. Look at the black plastic and under it in the potting material. The rear PCV hose often fails right where it makes the 90 degree turn into the intake below the throttle body.
 
FocusKnot

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2004 Focus Wagon, Zetec DOHC, Auto
Joined
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1,717 Posts
#5 ·
Oops! I just noticed that you put Duratec in your subject. I was thinking Zetec engine.

Check COPs for cracks and also check the PCV hose (unfortunately that is harder to replace than the Zetec).

BTW: Add Duratec to your profile so that it helps with future posts.
 
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FocusKnot
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