i just bought a 1998 ford ranger with 228000 miles on it seems to run fine has the 2.5 4 cylinder with auto trans. check engine light is on and code is a po 171 ive cleaned the mass air flow sensor and fixing to install new fuel filter any other ideas as to what the problem could be thanks for any input

 

Thats a lean code. I would start by spraying carb cleaner anyplace after the MAF, to include intake gasket area and see if the idle changes while your spraying. Could also be a partially clogged injector.

 

Welcome to FTE.

P0171 = System adaptive fuel too lean (bank 1)

Seeing as how you have a 4 banger, the bank one part doesn't figure in as you only have one bank of cyls, but the adaptive fuel part does & suggests that the computer has been adjusting fuel trim to make up for something thats been changing over time & its now at its adaptive limits & can't make further adjustments. SO, without more code clues to help us make an informed guess, the mileage on this puppy, unknown maintenance & repair history, a lot of possibilities exsist.

Rubber hose vacuum leaks (this would include the PCV valve & its rubber connections), clogged air filter, clogged fuel filter, weak fuel pump/low fuel pressure, dirty MAF sensor, dirty fuel injectors, lazy O2 sensor, leaking intake manafold gaskets are some of the things that come to mind that belong on your suspect list.

So, maybe consider beginning with an under hood inspection of All rubber vacuum lines & their connections for signs of dry rot cracks, or soft, mushy, loose fitting barb connections.
Maybe rig a propane sniffer to probe the intake manafold gaskets or hard to get at vacuum lines or connections for vacuum leaks & if any intake suspect areas are found, try re-torquing the intake fastners to spec, or replace suspecct vacuum lines.

If you have, or can come by a scantool that'll read sensor PID's to the computer, have a look at & post the short & long term fuel trim figures, O2 sensor response time & voltage switching range to see if its lazy, MAF sensor PID to the computer & do a fuel pressure test & post the test numbers for review.

Given the unknown maintenance/repair history, the mileage on this ride, I agree that changing the fuel filter is likely a good idea, but I would continue on & make sure All past & present due scheduled maintenance are brought up to date.

More thoughts for consideration, let us know how it goes.

 

ok so far have cleaned maf sensor sprayed over half a can of air intake cleaner in throttle body replaced fuel filter,airfilter,pcv valve put lucas injector cleaner in tank and still getting code po 171

 

OK, you've been busy!!!! Did you remove the battery B- cable, to wipe the computers KAM & corrupt fuel trim tables & the trouble code????

 

no i used a code scanner to erase code and turn light off is removing the battery cable the best way to remove codes ?

 

The code scanner is ok to reset the computer. Can't remember if it also wipes the KAM, so that the fuel trim tables are cleared, so the computer can begin to build new fuel trim tables after the MAF cleaning, PCV valve & fuel filter replacement, but i know removing the battery B- cable wipes the KAM & clears codes.

Do you have a code reader, or scantool that'll read live sensor PID feeds to the computer???? If it'll read PID's look at the short & long term fuel trim & O2 sensor PID's & post the Numbers.

If after erasing the code the CEL turned back on, that says that the computer says it still hurts some where, so do your vacuum hose inspection & propane sniffer test for vacuum leaks & let us know how it goes.

 

ok i done alot of checking no vacuum leaks changed idle air control valve no change took it to a friends son who is a mechanic did a fuel pressure check and found out only had about 40 psi of pressure thats running and not running just installed new fuel pump and strainer reset light and is running so much better put code scanner on to check and no codes showed up and had a green light on for a week stopped yesterday and bought gas took it on interstate and ran it at 85 mph put scanner back on no light but code po420 is on with yellow light on scanner could this just be bad gas or a cat gone bad

 

OK, you've been busy & done a lot of work, good to hear its running better. The P0420 code is for the cat converter efficiency being below threshold, maybe a cat going out, maybe its down stream O2 sensors sensitivity getting weak. So if you have emissions testing, before throwing a cat at the problem, have someone with a scantool that'll read live PID's have a look at the after cat O2 sensors switching range & speed, to see how its performing numbers look. If you live in cold country with lots of salt on the road, carefully check the electrical connections to the after cat O2 sensor for corrosion.

 

ok now i have another problem erased the 420 code got the green light now when i start the truck after it sits all night it runs good for a minute then it surges like its running out of gas surges for a minute then smooths out and runs good but still seems like its holding back if you get into the gas

 

OK, so do you still have the P0171 code, or is it gone now????

Did you remove, or clean the MAF sensor in place???? Did you let it cool & clean it with a non residual, plastic safe cleaner, formulated just for cleaning the MAF sensor, like CRC, or Valvolene MAF sensor spray cleaner product & didn't touch or poke its electrode & kept it squeeky clean on re-installation???? It's very important not to damage or contaminate its heated wire grid, so as not to corrupt its sensitive calibration.

Did you disconnect the battery B- cable to wipe the KAM & corrupt fuel trim tables, so the computer could begin building new tables after the work & did you go through the cold & warm idle relearn proceedure????

 

no the code 171 is history since fuel pump replacement i cleaned the maf awhile back before i knew it was low fuel pressure and no i havent disconnected battery cable after replacing fuel pump will give it a try and see but the way my luck is it will be something else lol thanks for everyones feedback

 

Perform this base idle relearn proceedure, Ford Truck Enthusiasts Forums - View Single Post - high idle problem so your certain the corrupt KAM fuel trim tables have been wiped & the computer can begin to build new ones after the repair & the computer has relearned its new cold & warm idle strategy & thus you'll have a good base line to proceed on your trouble shoot, if this doesn't help.
Let us know how it goes.