Can anyone give me any info on these 2 codes- PO171 and PO174. They are saying the system is running too lean. I have checked the voltage and listened with a steth to each injector and they all seem fine. I don't know what to try next. Thanks. 97 F250 LD auto 4WD 5.4L COP

 

You can look up the codes here:

http://members.monarch.net/dave_r/dtc's.htm

 

Thanks Myke, That gives me someplace to start.

 

Check for a vacuum leak. A good place to start is the hose from the pcv to the throttle body.

 

Also, try cleaning the MAF.

 

Hey Myke- You hit the nail right on the head. I pulled the PCV and put my thumb over the end and got a nice telltale sucking sound from behind the engine at the firewall. The hose was broken where it makes the bend into the IAC valve; an impossible spot to see and almost impossible to work on. I had to have my wife put the new hose on because my hand could not fit back there. Thankfully it was just a matter of pushing the new hose on. You'd never spin a wrench or a screwdriver back there. It cost me $25.00 at my local Ford dealer, which is not bad because it includes the PCV. I tried to buy just the rubber piece on the end, but the whole assembly is one part #. Anyway after I got it on I let the engine run and shut it off a couple of times to let the computer figure out that the human repaired it and the idle is back to a nice and smooth 750 RPM or so instead of fluctuating between 600 and 1000 and seemingly trying to die at every stop sign. Going to my local auto parts guy to clear the codes and hopefully not see that CHECK ENGINE again. If I do my next thing will be cleaningthe MAF. Thanks so much guys. '97 F250 LD auto 4WD 5.4L COP

 

Glad to hear you solved your problem. You can clear the codes by disconnecting your battery, drinking a beer, then reconnecting it. The beer is the most important part, so make sure you don't forget that part.