For the last month, I have been getting the P0171 and P0174 codes. I replaced the PCV, replaced the fuel filter, checked vacuum hoses for cracks (although I only found two hoses -- PCV hose and one other). I also removed and cleaned the MAF two times. I inspected the air fliter to throttle body hose for cracks and found none.

Any other ideas? Could it be the oxygen sensors? Leaky gaskets? Any ideas would be appreciated before I hand it over to the Ford dealer.

 

my 2000 explorer just threw both of those codes. i have cleared them twice just to see if its a fluke, but it seems to throw the codes at idle. where did you start?
any help?

 

I had the same issue with my 99 Explorer. I thought the O2 sensor as well and the first time replaced the codes were clear but returned veryt quickly. (week or 2Turned out to be my MAF (Mass Air Flow) Sensor. Mine was dirty and cleaning it worked just fine, but could also be faulty.

 

If my MAF is faulty, will driving around with it disconnected keep the codes from returning? Will it damage the vehicle?

 

If you unplug the MAFS you wont run at all. Have you looked at the IAC?

 

Actually, I unplugged it and it ran fine at idle with no MAF. Is this indicating that the MAF is faulty? Could the IAC cause these CEL codes?

 

It WILL run with the MAF unplugged, but it will set more codes for lack of MAF signal. Now if you leave the MAF plugged in, but disconnect the air tube.. then it won't run.

Your P0171/P0174 codes are being caused by leaking intake manifold gaskets. When the vehicle is cold, start it up and once RPM stabilizes immediately start spraying carb cleaner or intake cleaner around the mating surface of the intake and the engine. If you notice a change in idle while spraying, they are leaking for sure. Sometimes they can still leak but still pass this test as well.

I've done several of these for that specific problem. Can also cause cold start issues. Good luck!

 

Any idea how much it costs to replace the intake gaskets? That's not a job I can do myself.

 

Oops yea my bad! I was thinking about no MAF and no intake tube. I just did the intake gaskets on mine and it's not a too hard of a job. A local mechanic estimated about $500-600 to do the job I did it for $200. Dont run with the MAF unplugged or you will get all kinds of codes! If it were an 02 sensor you would get a code specific to the 02.

 

I've been getting those same codes on a 2001 Sport 4.0 sohc, I am getting the gasket set and I am going to attempt the job myself. Any pointers from any of you
Veterans out there that have done hundreds of these..
Thankyou for your help.

 

I just had the same problem and took it to the local shop. They had to replace my gaskets and my intake manifold because it was warped.

 

What did they charge you for that job?

 

$390 out the door

 

Well I thought i had the problem fixed the mil came back on with the same codes 5 miles later. Reset the computer and came back on within 5 miles. Did this several times the took it back to the shop. They hooked up a smoke machine and smoke was billowing out from the back of the intake. Now what is back there that smoke would come out of.

 

sounds like they either left a vacuum line disconnected back there, or they cracked the intake on installation.