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Ron Z.
Ron Z., - Ford Tech -
Category: Ford
Satisfied Customers: 17799
Experience:  18+yrs experience. State Inspector & Ford Diagnostics/Repair
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171 and 174 codes. engine cuts off at stop lights. But

Customer Question

171 and 174 codes. engine cuts off at stop lights. But cranks up easily and proceeds forward.
JA: Just to clarify, what are the exact lights you're talking about?
Customer: Cuts off when I brake.
JA: What is the model/year of your Ford?
Customer: 1999 f150
JA: Are you fixing your F150 yourself? What have you tried so far?
Customer: Yea. Nothing yet.
JA: Anything else you want the mechanic to know before I connect you?
Customer: 250,000 miles.
Submitted: 21 days ago.
Category: Ford
Expert:  Ron Z. replied 21 days ago.

Hi! Welcome to JustAnswer. I'm Ron Z and I'll be helping you with your question today.

The P0171 and P0174 are pointing to both banks running "lean". When these codes are set together, there are a few different things that can cause this issue. First- check the Fuel Filter. Remove the filter and try to blow through it. Any resistance and the Fuel Filter will need to be replaced. If the fuel filter is ok, a fuel pressure reading should be taken to ensure the fuel pump is working at normal capacity. If these check ok, next move onto the air filter housing, duct and filter element. Inspect the duct for any cracks, holes or loose connections. Make sure the filter box is sealed tightly and correctly. Inspect the filter element and make sure it is not excessively dirty, restricting air flow. With the engine running, listen for any "sucking" or "hissing" noises. Inspect as many vacuum lines on the top and rear of the engine as you can see, looking for any cracks, holes or loose/missing connections. Make sure there are no leaks in the exhaust system. If these check ok, an intake air leak should be done to make sure there are no leaks. With the engine running, carefully and sparingly spray some throttle cleaner around the base of the intake. If the engine responds, this is a sign of a leak and the intake gasket will need to be replaced (make sure to visual inspect the manifold itself for any cracks at this time as well). If these all check ok, then the problem will lie in the Mass Air Flow Sensor. Inspect the electrical connector for any loose, broken or damaged wires. If the visual inspection checks ok, then there IS a "cleaner" for the MAF sensor, however, in experience, it's usually not a 100% fix, and when it does work, it's usually not for long, and MAF replacement is usually necessary. Please remember to leave a rating using the 'stars' or click 'Accept'. A 5-star rating is much appreciated! Rating or accepting my answer does not cost you extra.

Expert:  Ron Z. replied 19 days ago.

Hi! I noticed this thread was still open, so I wanted to check in and see how you were making out? Any other questions you had? Was there something you wanted addressed that I may have missed in my answer? Did you find my answer helpful and informative?

Expert:  Ron Z. replied 15 days ago.