P0171 & P0174

[freak]

I have a 4WD 2000 XLS 4.0 OHV 5sp 160,000mi. Last winter one day it was something like -5F and it started running rough and had the lean codes. Went away when it warmed up. Figured it needed upper intake gaskets. Cleared the codes. This year I get the codes again. So I replace the upper o-rings and gasket and injector o-rings. PVC sounds ok. Installed a new IAC (to get rid of IAC noise) Cleared the codes. Codes come back the next drive. Also my idle (warm or cold) is high. At a stop light with the clutch in it is about 2000rpm then it will slowly drop (sometimes) to maybe 1000/1200 which is still too high. The cable is not stuck. I have checked everywhere for a vacuum leak cannot find one. (I would love to have a smoke machine!) What should I look at next?

 

[BrooklynBay]

Welcome to this forum! Check # 51 in my list of useful threads for more information: http://www.explorerforum.com/forums/showthread.php?t=177975

 

[alan21]

Those codes relate to the outside temperature sensor
Alan

 

[freak]

No... they're system too lean bank 1 and 2.

 

[aldive]

Those codes relate to the outside temperature sensor
Alan

Naw.

 

[briwayjones]

How many miles are on the spark plugs? Worn spark plugs can cause those codes and a lean condition.

 

[ThePhoenix]

that would explain multiple codes at once right?

 

[briwayjones]

It would explain at least those two codes at once. I had very worn spark plugs and had those two codes. Flipped the the O2 sensors around they weren't the problem. Finally put new spark plugs and wires on and presto the codes were gone and never came back.

 

[freak]

Seems ok now. Here's how I fixed it... Figuring that there was a vacuum leak I fashioned a plug for the intake hose at the air filter. In the plug a put a air hose coupler. Then I applied about 3psi to the intake. I could feel and hear air leaking from the IAC which is normal. But I could also hear it down below by the EGR valve. Finally figured out that the EGR gasket was bad. Initially the plenum gaskets were bad and I replaced them. To get the plenum off I had to remove the EGR valve. (Didn't realize at the time that I could have left it on because I didn't know that the EGR tube was just stuck in the plenum) Anyway I must have damaged the EGR gasket as I removed the EGR. To get the EGR off to replace the gasket I had to heat it with a torch by the nut that connects the exhaust tube. Figuring the heat could have damaged the EGR I replaced it too. Now my idle is correct (under 1K) and once I clear the codes tonight I don't expect to see them again.

 

[BrooklynBay]

Thanks for the troubleshooting information!