Code P0171 and P0174 during very cold weather only

[Eagle_Scout2002]

Well an update on my engine issue. Code never came back after temperatures warmed back up. Came back on again last Friday. Temperatures hit the double digit negatives. BRRRRRR!!! Well anyway, in the mean time I took a real good look over the engine. Found a minor coolant leak on the left side intake mainfold and a minor coolant leak at the cylinder head on the right side. Both leaking external. No coolant in the oil and not burning coolant. Been having to add a gallon of coolant into the surge tank about every 6 months or so. Just never got around to looking for the leak. Ordered a head gasket kit and head bolts from Amazon.com. Cheapest place I could find them. Same part number as what Napa, Autozone, and Rock Auto sold. Going to flush and change the coolant, thermostat, oil change, fuel filter, and some other maintance items while I am doing the head gasket. Hopefully I will get around to it this month, and if not it will be next month. Just have to find a weekend to be able to do it.

Ray

 

[Eagle_Scout2002]

Well I finally got around to replacing the head gaskets. Engine had just under 222xxx miles on it. Pulled it apart and inspected everything. No cracked heads, everything looked good and clean. Could still see the cross hatching in all the cylinder walls from the original machining. Really happy about that. Replaced the air filter, fuel filter, oil filter, oil, coolant, thermostat, and pcv valve. Cleaned everything and replaced all gaskets. Torqued the head and intake according the the service manual. Ran good before hand and ran a little better after. The codes were still coming on before hand and now they are gone.

Ran great for 4 days and now I have another issue. Now it does not want to idle properly. It idles at 1500 - 2500 rpms. No driveablility issues. Runs and drives great. No codes. Just idles high. Tried searching and did not come up with much of anything on this issue. Any suggestions anyone? Tomorrow, I am going to give everything a really good look over and see if something came loose or anything. Well thanks everyone.

Ray

 

[Capt Marvel]

I had the same P0171 and P0174 codes appear in -14 degrees C weather so I started with the MAF sensor and cleaned it with contact cleaner, but it didn't make any difference, the codes returned as pending codes. Following the advice found here I noted the fuel trim values at idle and at 2500 rpm and found that things were much worse at idle. So I went and bought some carb cleaner and started spraying around the intake connections and PCV hosing and no changes in RPM were detected. I found what looked like a small crack in the elbow of the PCV plumbing and sprayed right down the hole. No change in RPM. My advice is that it may depend on the formulation of carb cleaner you're using so don't assume no change is good news. Anyway, being a Saturday and the parts counter is closed, I removed the elbow, cleaned it off with the carb cleaner and taped it up with electrical tape. Sure enough the fuel trim values now hovered around 0.0%. After the weekend, I ordered a new hose assembly worth $45.00 as you can't just order the elbow.

Thanks for the great advice everyone, problem solved. The carb cleaner still came in handy and was useful all the same.