I have been reading a number of threads on this forum that have dealt with diagnostic codes P0171 and P0174, but very few that say anything about P0174 only. This is my problem. Vehicle is a 98 F150 4.2 V6. From what I have read, it would seem that if only one of the two codes appears the problem is probably not vac related or MAF related because that would affect both banks.

Does anyone have any ideas where I should start when only having the P0174 code? Any help would be greatly appreciated.

Bob

 

Look for a vacuum leak first - clean your MAF anyway, doesn't hurt. Replace the PCV valve and make sure you check the whole line out very well for leaks!!

After all grommets and lines are checked + plus the MAF cleaned - It leaves the intake gaskets , that job is easy but time consuming.

 

I started with both codes, then did the standard checks and repairs, turned the CEL off, ran 700+ miles, then P0174 only came on.
(1) cleaned, MAF "AGAIN", with CRC elec. cleaner, (had really good pressure out of the can). Everthing in the MAF looked new when I was done.
(2) Replaced the entire PVC line assembly ($28.00) from Ford.

Been running great with no CEL for the last 2 months. I check it every now and then for pending codes w/ my scanner and I have nothing, all green lights,and alot better power and MPG.

Unfortunately, your dealing with a code that has alot of possible fixes. Try to find the thread I started for this problem (FEB/MARCH-2008). It has alot of answers. Got me through my problem.

Good Luck,

TJK

 

I attempted to clean the MAF, but hit a snag after I got the assembly out of the air horn. One of the phillips head screws holding the MAF sensor to the assembly has had it's head filled with a hard plastic substance, making it impossible to remove. I suppose Ford doesn't want it removed and cleaned. Anyway, I sprayed CRC every which way I could and hopefully did some good.

I also sprayed all vac lines and vac line connections with starter fluid and go no appreciable increase in rpm. However, the rpm of the motor at idle is going up and down a little, which is usually associated with a vac leak. My next question is where is the pcv on my 98 4.2 liter engine. I have seen threads here that say it is on the valve cover and other threads that say it's on the intake manifold. If it's on the valve cover it must way in the back in an very difficult location.

Once again, any help will be greatly appreciated.

Bob

 

Cleaning the MAF only requires you to access the unit by removing the air filter then spraying the cleaner that's formulated for this. CRC maf cleaner is my choice. What ever you do don't touch the wire in there or you will be getting another MAF to replace it.

 

Ford had a huge problem with the seals around the isolator bolts leaking on the upper intake. They have a kit at ford with a redesigned intake with new bolts that will most likely fix your problem. Its around 300 bucs took me an hour to change it and the codes havent been back and the truck runs smoother. It's been 8 months so far.

 

There is no reason to open up that MAF Sensor. You should be cleaning just the wires at the end of the sensor which are visible as soon as you seperate it from the air filter housing. You do not need to remove the sensor from the
"black plastic housing", that connects to the throttle body.
The hard coated plastic in the screw is there for a reason. It is saying "stay-out".
That setup has very fragile wiring, actually all MAF's do.

Good Luck....