I have a 2002 F150 5.4 Triton 4x4. A couple of years ago when the weather turned cold my Service Engine Soon light came on and the auto parts store ran the code and told me to spray the Mass Airflow Sensor and I did and it cleared right up. This year the first week it got cold (~10 degrees F.) The light came on. I tried spraying the MAS with no luck. I went to the auto parts store and they checked the code and said it was a PCV valve. I changed that with no effect. They checked again and said it's too lean and maybe an air filter. No luck.

After running about 20 minutes it starts to run rough. Sputtering and the Service Engine Soon light even flashes when it's running rough. I took it warm to another parts store and they checked it with their little computer and now said O2 sensor(s) and maybe #8 coil pack. I bought the front O2 sensor and loaned the tool. I changed it out and the truck still runs the same.

A buddy loaned me his Actron computer today and I checked and got 3 codes.
1/3 P0171 MOD $10
Bank 1 System Too Lean

2/3 P0174 MOD $10
Bank 2 System Too Lean

3/3 P0308 MOD $10
Cylinder 8 Misfire Detected

 

Fix the misfire first, erase the codes and see if any come back.

 

...and fix your vacuum leak.

 

You have been shotgunning parts at it based on the advice of a parts store. You will get much better code interpretation HERE.

Example - you don't replace O2 sensors for a lean code. For lean codes both banks, you have a major vacuum leak - the most likely suspect is the elbow on the back of the intake on the line coming FROM the PCV valve - not the PCV valve itself.

A specific cylinder misfire MIGHT be the coil, but it can also be the spark plug among other things.

 

OK, I will investigate the vacuum line from the PCV valve and change the spark plugs Any recommendations on spark plugs? I hear the #8 coil pack is a tough one to change out.

 

Motorcraft plugs, no antiseize, 28 ft/lb torque.

 

So I was going to give up and let a professional do it. I took it to the shop this morning and they said they wanted to charge me $550 for a full tune-up with plugs, PCV valve and EGR valve. I told them I can't afford that right now, going to pick it up at lunch.

So I think I will get it in a warm garage and try to find the vacuum leak, replace spark plugs and try clearing the codes.

Thoughts?

 

That price is typical I think. Several years ago, when I was still working away from home, I checked with a Ford dealer and they wanted $240 labor to install new plugs plus $10 each for the plugs. With EGR, it's about normal for a dealer. I ended up replacing my plugs when I took a week off and drove back home. It took a while because the plugs are so hard to get to. Like everyone says, you most likely have a vacuum leak. That would be the first thing I would tackle and I would put a bottle or two of Gumout for high mileage engines in the gas to help clean the injectors. Then I would change the plugs.

 

Get maf cleaner and spray the vacuum areas, if you have a leak it will sputter. Did this to find a leak on my 370z.

 

No, it won't, the computer is too fast.

 

No, use an unlit propane torch and watch the fuel trims with a scanner.

 

You are wrong. The propellant in the can does the same as the butane in a butane torch.

 

thanks for the tip glc, I was not aware of that one.

 

I am very correct. You have to do it as glc suggested, you CANNOT "spray and listen" as you had suggested, the computer is too fast. You have to watch what the computer does. Any flammable will work, ie, brake parts cleaner, intake/carb cleaner, unlit torch, etc.