I picked up a 93 Ranger 4x4 from my father in law for 1K bucks. it has 134,000 miles with the 4.0L 5spd. it needs some help.

it has been missing and chugging when going down the road so i replaced the plugs/wires, cleaned the MAF sensor, new air filter. this made a huge difference and it runs much better now, however, it feels like it has more power but something is holding it back. I had a 91 4.0 5spd that i bought new so know what this engine is capable of.

i have codes: 172,173,176,177,185,186,528









I've been told the flames add 10 HP too

 

Any trouble code clues stored in the KAM???? If so, post All code Numbers.
Are the O2 sensors OEM, if so, check their switching range & speed, as most are ready for replacement around 75-100K miles. If you have, or can come by a scantool that'll read fuel trim, have a look at that & the upstream O2 sensors, to see how things look & post the results for both cyl banks.

EDIT: Woooops I missed the posted codes, they sorta blended in with the house roof line. You definitely have a fuel trim problem. Did you remove the MAF for cleaning & did you use a plastic safe, non residual, cleaner formulated just for cleaning the MAF sensor, like CRC, or Valvolene MAF sensor spray cleaner & did you allow it to cool before cleaning, didn't touch the sensor & kept it squeaky clean when re-instaiilng???? The P0185 code is for a lower than expected MAF output, which would suggest it may still be dirty & not properly sensing air flow over its heated element.

 

check your codes here:

OBD-I Diagnostic Trouble Code (DTC) Applications - Ford 3-Digit Codes

 

i used a cleaner specifically for MAF sensors. it was done in the morning before the truck was even started. definitely did not touch any part of the sensor, it was extremely dirty before i cleaned it. he needs this truck until september so it will be weekend work until i can get it home. some of these codes seem contradictory, 172,173 says its rich and lean- i thought i cleared them after the oil change and before the road test but perhaps i didnt. i will clear them and see what i get.

 

With the MAF sensor dirty, it was sending the computer corrupted info about true airflow into the engine, so the KAM fuel trim tables are likely corrupt too & should be cleared by disconnecting the B- battery cable for a few minutes, so the computer can begin to build new fuel trim tables with the cleaned MAF sensor input. As this procedure also wipes the cold & warm idle strategy, take the time to perform the cold & warm idle strategy relearn routine here Ford Truck Enthusiasts Forums - View Single Post - high idle problem & that may prevent idle & driveability problems. Let us know how it goes.

 

Another thought, seeing as how the MAF sensor was dirty & its only to see filtered air, be sure to inspect the cold air filter box & air tube fitting between the air box & MAF sensor for correct fit & that all fasteners are properly tightened.

 

got the truck at my house for the weekend. some things i've noticed is that it runs better than it did, but it still is hesitant. kinda chugs a bit when cruising. not sure it is missing but hard to tell. also when you are picking up speed, and it is kinda hesitant, if you really give it the gas she takes off pretty good. almost normal i'd say. i stopped by the parts store and picked up a fuel filter. i'll put that on this weekend before it goes back to him for a couple weeks. i also found out that he put in a new fuel pump and found the filler neck was cracked pretty bad. he went to get a new one and didnt want to pay the 100 bucks so he put on a radiator hose. he said it leaks if you fill it to fast, or all the way. i found i can get one on ebay for under 40 so that will be done soon.

 

ok, played with the truck today. if you drive normal it is sluggish. if you floor it she takes off and runs great. sometimes you will be cruising along going great, then for no reason it loses a little power and you have to either give it alot of gas or downshift. i know the power is there but at cruising speeds it feels weak. so i'm thinking fuel problem so i put in a new fuel filter and went to test it and it felt pretty good at first. then back to what it was doing before. i was checking out under the hood and found what looked like cracks on the coil so i put in a new coil. that wasnt it either. so i cleared all the codes and went for a drive until the engine light came on.

codes now are:
my book says
157 mass air flow sensor fault-low voltage
176 HEGO (ho2s) sensor fault/always lean
173 HEGO (HO2S) sensor fault/rich

I have an exhaust leak on the right bank at the manifold i think. i'm thinking this would be a lean fault because its before the sensor? not sure what the rich fault would mean. what would low voltage mean on the MAF? should i replace it? i cleaned it before but it could be bad.

 

I agree that the exhaust manifold leak that's up stream of the O2 sensor could affect its output reading to the computer.
The MAF sensor low voltage code could mean its still dirty. Did you remove it to clean, so you could get at both sides???
Did you measure V Ref to the MAF sensor???

 

i did pull it out and sprayed it pretty good with maf sensor cleaner. i did not measure voltage to the sensor. i will clean it again, i am reading about testing it now. from what i've seen online i think the maf sensore is my problem with it. well, one of my problems, i have a stuck caliper that is on the docket for tomorrow. so i'll do brakes and caliper and more maf testing.

 

OK, that sounds like a plan.
On the stuck caliper, be sure to give the brake system a good flush & Motorcraft PM-1 DOT-3 fluid is recommended, as its of high quality.

 

did some testing on the MAF this morning. all voltage was normal as far as i could tell. i decided to change it anyway. for the same price i could either replace just the sensor or the entire thing housing and all. so i replaced the whole thing. Bingo! that was it. runs a lot smoother and i can actually use the cruise control now and it will keep up. replaced the caliper and as a bonus the brake pads were fine so it was an easy day. cleaning up all the tools and putting them away were the hardest part haha. Thanks pawpaw for all the help!

 

Allright, good trouble shooting & feedback. Way to hang in there & persevere to see things through to a successful ending & to hear all seems well & your on the road again!!!!

 

Reviewing all we talked about, did you get around to inspecting the air box, air filter, air tube & how it all fits together???? The air filter, air box & air tube need to fit together right & should be all buttoned up properly using all the factory fasteners & be without damage, so the new MAF sensor doesn't see dirty air & have its PID output to the computer about true airflow into the engine get corrupted again!!!!

 

yep, i did take the tube right off the intake and check the bottom for holes or split seams. everything is tight. new air filter, cleaned out the box, really glad this took care of it.