Po171,po174

[Robert1966]

My expy runs rough,almost stalling,only when the outside tempereture gets cold, i get code 171,174. In the summertime car runs great, no codes. When its cold outside, engine runs rough no matter how long i drive it for. What do y'all think ? Why only when its cold outside do i get these codes?

 

[1955moose]

Codes 171 and 174 are a lean condition on banks 1 and 2. Try cleaning maf sensor mounted on tube next to air filter. Use a quality electrical cleaner from auto or electronics store. Be sure to shake out or better use air to blow dry gently before reinstalling. It's bazaar that only when cold you get symtoms. The upstream oxygen sensor can also be part of the equation. You can have one of the repair shops in your area run the diagnostic when it's cold out, and watch the performance of the oxygen sensors to see if their within specs. If you do replace o2 sensors or maf sensor, spend the extra and buy Ford. Aftermarket electrical can be hit and miss. Keep us posted what you find. Also one other thing make sure you have no intake or Exaust leaks. This adds to your problem.


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[jdecker]

It's your intake gasket

 

[1955moose]

If he had an intake gasket leak, he'd have shaking in any weather, not just cold. Robert, the easiest and oldest test of intake leak checking is use a can of carb clean while it's running rough, spray around intake gasket a little at a time. When you hit the leak motor will smooth out and eureka you found it. Do the same around any hoses or gaskets you suspect. Good luck.


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[Skauber]

My first thought would be MAF sensor, it may be negatively affected by the colder air. Since it's only during cold weather, I don't think it would be intake gasket. If it was due to colder metal, it would smooth out and stop leaking when the engine warms up.

 

[1955moose]

That's what I said. An intake leak will rear it's ugly head the minute the truck warms up and fuel leans out. Guys did I read right the maf sensor is connected with the iat sensor. His intake air sensor could be on the fritz. Robert, I'd test wiring up to it, and replace if necessary. Their not that expensive. Maf sensors are. Let us know


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[Skauber]

Iat and maf sensor is one and the same on the 05-06 at least, not sure how it is on 03-04, or what year or motor the OP has..

 

[1955moose]

His tag line says 2003, Robert is that the right year of vehicle in question?


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[1955moose]

Looks like 2003 is a separate screw in item. He's still needs to do some troubleshooting first.


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[jdecker]

Had the exact problem on my 03, lived with it the first winter - ran fine during the summer no codes or anything. Next winter took it in before even driving or looking at it Ford tech told me it was the intake gasket, said it's common and they get lots every time it gets cold. Replaced the gasket, problem solved. I will say mine was worse the second winter it got to where it would die occasionally when idling

 

[1955moose]

Wow, never would have guessed an intake gasket was weather sensative. But I guess if cold air is sneaking past an area that's supposed to be air tight. Could be. Happened to two of you. Did new gasket/ manifold totally take care of problem?


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[jdecker]

Tough to diagnose here are a couple of links were owners spent up to $4000 chasing it before doing gaskets:
Cold Air = Rough Idle - F150online Forums

http://www.fordf150.net/forums/viewtopic.php?t=65607

P.S. yes it totally alleviated the problem

 

[1955moose]

Could be because intake is plastic, others are aluminum or cast iron, it doesn't expand in the cold weather, causing a leak when it gets older or weak. Amazing a $40,000 plus truck and use plastic when aluminum would probably last life of vehicle!


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