P0171 and P0174 after Engine Installation - Runs Fine

[50chevy]

I am new to posting here but I have been doing a lot of thread reading lately. I have a 1998 Ford Ranger 3.0L automatic and took the engine out last week to re-gasket it and install a new 4r55e transmission (from an Explorer). It has 182,300 miles. I replaced every gasket in the engine and reinstalled it. I had no parts left over. I turned the key and it started immediately and idled. I had it on a lift and ran it for about 30 minutes to check for leaks before I drove it. I took it for a 15 mile drive and it ran great. When I got home I turned it off and came back about 10 minutes later and drove it again. In about 300 feet the CEL lit up. Codes p0171 and p0174. The truck starts immediately, idles fine (about 1000-1100 rpm, I've had it 4 years and that is where it idles with NO codes). I checked for vacuum leaks by spraying brake cleaner everywhere and no idle changes. It has new gaskets, new PCV, new PCV hose, new EVAP hose, new injector o-rings. If the light wouldn't come on, I would not think anything is out of the ordinary. This truck is my baby and I know it very well. When I clear the codes, they come on after I start the engine after driving a while on the previous trip (with no CEL during that drive). It has about 100 miles on it since the engine install. Any suggestions would be helpful. Thanks.

 

[James86]

Its the O2 sensors.

 

[50chevy]

I replaced both of them at the same time as the engine work. They are Ford Motorcraft. Most forum replies indicate the O2 work when p0171 and p0174 are thrown becuase they are able to detect a lean condition.

Does the ECT sensor have any effect on lean conditions? I broke mine during the engine swap and bought a NAPA replacement but it looked a little differect from the OEM but still plugged in fine. I also cleaned the MAF.

 

[JP02XLT]

P0171 & P0174 are lean conditions on Bank 1 & 2, My truck will throw these codes along with a P0000, occasionally if I let it idle & if the temperature is near or below 15 deg, It also seemed to pop up more lately as I have been experimenting with a fuel mixture of gas & e-85. I had never seen this in temps above 40 deg. My O2's read normal & function as they should, I have data logged & graphed their cycles to be sure they are changing as often as they should. Even checked at idle with a wide band O2, the idle AF is spot on at 14.7, I have not been able to capture it on the wideband with the SES light on to see if anything is different then. Personally I think the Ford ECM's software combined with running strictly off MAF that they have a difficult time adjusting to winter blend fuels and the below normal cold temps.

Let me know if you find out anything, I have not been able to find out anymore helpful info about this scenario. I have checked for vacuum leaks & air intake leaks past the MAF as well. So for now I simply clear the codes to shut off the light, My truck runs and idles perfect otherwise, even with the light on.

I don't think this is an O2 issue in your case & I know its not in mine.

JP02XLT

 

[pcollins]

It is NOT the O2 sensors, a lot of people replace these when both codes pop up. What is the chance of 2 O2 sensors kicking it at the same exact time? Not big.

You need to clean or Change the MAF, and check for vacuum leaks. If both of those are good, you most likely have an Intake manifold leak. I just got these codes about a week ago on my 4.0, cleaned up the MAF and so Far, so good cause they aren't back. (knock on wood)

 

[50chevy]

I believe I may have solved the issue. I did find a vacuum leak where the EGR connects to the upper intake plenum. I replaced the gasket and reset the PCM again and went for 3 test drives this afternooon. The CEL is still off. The engine idles really smoothly at about 950-1000 rpm now. I'll keep you all informed if any other problems arise. Thanks for the help.