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Discussion Starter #1
Hello to all.
My problem is this. The Focus idles "fair" most of the time. Drives fine off idle. But when I come to a stop light, the car bucks hard and begins to idle very badly. Almost to the point of shutting off. If I place my foot on the brake with car in drive and give it gas, it clears up for a min and then reverts back to rough idle. It drives fine while off idle. I pulled a P0171 Lean bank code from the ecu.
Any suggestions are greatly appreciated.
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Most likely a combination of things. Are you planning on repairing this yourself? If so, it would be good for you to go through the basic things that fall under tune-up.

1) Fuel filter: often overlooked, but has a 20k mile service life, your fuel pump will last longer if you change these on schedule
2) Spark plugs: factory plugs last about 80k miles if no other issue presents itself that might limit their life- like a lean condition.
3) Spark plug wires: for daily driver DIY repaired vehicles I recommend the lifetime warranty plug wires from any national chain store. After purchasing these, new ones can be swapped for the old without costing you anything. You buy a new set, and return the old ones in the box to get your money back- very important, no returns without the box.
4) Air filter: has a 25k mile service life if it's a paper filter
5) Mass Air Flow: Clean with MAF spray cleaner, and then reinstall. These get dirty over time. You'll need a T-15 torx driver, and a can of MAF spray cleaner. Be sure to spray inside the little hole in the corner where the resistor is.
6) PCV valve: should be checked every 25k miles, and this is most likely what is causing your problem. The vacuum hose that feeds the PCV valve has rubber parts that dry rot and collapse or crack and leak. It causes a low idle, and sometimes a lean code.

These are the things I'd check into before I assumed I had a larger problem. I know it's a lot, but it's really just one day worth of home auto repair as most of these are 30 min jobs at best. You can purchase a new PCV valve line from Ford for like $40, or simply purchase some hard plastic elbows and appropriate sized rubber line to connect to the factory plastic line if it is not damaged, or simply replace the whole line with rubber. That should last about another 5 years, and cost about $10. Do not bend rubber hose sharply- it will collapse, that's why I recommend purchasing the hard plastic 90 degree pieces.
 

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All that stuff... My timing belt had stretched a bit after 128K miles... the timing is/was off a bit.


Dorman makes an improved version of the PCV hose that can be had at a better parts store. Most don't know about it, so say Dorman, and they can likely find it.
 

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Most likely a combination of things. Are you planning on repairing this yourself? If so, it would be good for you to go through the basic things that fall under tune-up.

1) Fuel filter: often overlooked, but has a 20k mile service life, your fuel pump will last longer if you change these on schedule
2) Spark plugs: factory plugs last about 80k miles if no other issue presents itself that might limit their life- like a lean condition.
3) Spark plug wires: for daily driver DIY repaired vehicles I recommend the lifetime warranty plug wires from any national chain store. After purchasing these, new ones can be swapped for the old without costing you anything. You buy a new set, and return the old ones in the box to get your money back- very important, no returns without the box.
4) Air filter: has a 25k mile service life if it's a paper filter
5) Mass Air Flow: Clean with MAF spray cleaner, and then reinstall. These get dirty over time. You'll need a T-15 torx driver, and a can of MAF spray cleaner. Be sure to spray inside the little hole in the corner where the resistor is.
6) PCV valve: should be checked every 25k miles, and this is most likely what is causing your problem. The vacuum hose that feeds the PCV valve has rubber parts that dry rot and collapse or crack and leak. It causes a low idle, and sometimes a lean code.

These are the things I'd check into before I assumed I had a larger problem. I know it's a lot, but it's really just one day worth of home auto repair as most of these are 30 min jobs at best. You can purchase a new PCV valve line from Ford for like $40, or simply purchase some hard plastic elbows and appropriate sized rubber line to connect to the factory plastic line if it is not damaged, or simply replace the whole line with rubber. That should last about another 5 years, and cost about $10. Do not bend rubber hose sharply- it will collapse, that's why I recommend purchasing the hard plastic 90 degree pieces.
I have the same exact issue going on with my ZX3.
I replaced the right rear (under throttle body) pcv tubing and also replaced the pcv valve as well,but not the hose the pcv valve is attached to.
Should the hose the valve is attached to be replaced as well?
Is it common for this one to collapse too?
I cannot feel under that one to tell if its bad.
Help and input appreciated!
[scratch]
 

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Discussion Starter #5
Thank you for the replies!!!!!!!
whythinknot, I have done items, 1,4,6. The hose was bad at the manifold and ha been changed prior to non fact. I did the same thing. To clean pcv valve, I filled the tube up with carb cleaner a few times and started car. Ran better with high rpm's and tranny started acting funny. (I have thread on that also). TPS is registering 20.% at idle. I will do plugs and wires (very good tip on lifetime warranty). the mass airflow I just sprayed carb cleaner thru ait and allowed for it to dry. Not the lil hole area.

@ vexman. Thank you also for that tip. When car is idling, she idles smooth for the most part. When your timing belt was stretched, was your timing retarded. Just thinking, seems like the timing is retarded based on acceleration. hmmm?

Thanks again for the replies.
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