P0171/P0174 Mass Air Flow sensor nightmare

[dangilroy]

just_randy,

In the thread you posted to, Brian1269 has my exact same problem. I will dig into some of the issues stated there.

I have to admit I replaced my MAF, because I thought that was the problem. I didn't know you could clean it, and replacing it didn't solve the problem.

But the vacuum leaks, I haven't checked into thoroughly.

 

[Just_Randy]

I got pretty excited when I saw the bouncing numbers and how they correlated to the air leak. I felt like I was on to something.

Always worth a shot to connect a voltmeter to the MAF and see what the numbers are. I'm pretty sure the reading should be a steady one.... at least at idle!

 

[BrokeRecord]

I had the same codes on my 99 ~ 4.0. It would start when temps were in 30s and go away in the Spring. It happened everytime I cold cranked the 1st time every single day. I carried my code reader on the passenger seat and plugged it in and removed the code every day. Mine was dribbling gas out of one injector and would backfire on start up.
So far no trouble with my 07.

 

[lhc_cj7]

The wifes 03 expedition had a real bad stumble at idle and would even die at stop lights. Found a vacuum hose on the back of the TBI with a hole. The daughters 94 mustang had the same deal. At idle I could actually hear the the vacuum leak coming from the back of the intake. Shot the area with carb cleaner and new I was right on when the rpm's increased. The vacuum hose was rotted and split. Both hoses where ran from the valve cover to the back of the intake. Replaced and all is good.

 

[TomTom59]

Lean Bank 1 & 2

I've heard of leaking intake manifold gaskets leaning out the mixture on 4.0s. If a two-piece manifold disassemble and replace gaskets and don't overlook a leaking throttle body to manifold gasket. You have a leak somewhere after the MAF sensor. Also if over 60k miles on it, replace the O2 sensors as well.

 

[Rangerboy]

My 95 Ranger is cutting out! When I take off and especially under a load. It's not throwing any codes and I've checked and cleaned the MAF and changed out the throttle position sensor. I've also changed the fuel filter and the fuel pressure regulator. Last year I went through the EGR system and all the hoses and tubes. I've also changed hoses that connected my purge system. I've got a new purge solenoid and purge valve. I haven't changed the cannister. I've heard you can just disconnect the hoses from the cannister and run it directly into the engine compartment? I don't know if that could even be the issue. I think I've checked a lot of the hoses just don't have a clue what else it could be???

 

[gator1gear]

EVERY single time My truck has thrown the same codes, a Fuel Filter has fixed it. Not saying that's your problem, but it's worth a check. 2000 Ranger. I spent days searching for a vacuum leak, cleaning the Mass Air meter etc...

 

[okietheranger]

My girlfriends explorer had the same codes but it ran great. Found out that the fuel pressure would drop just a couple psi when the engine was above idle. Replaced the fuel pump, I guess the psi that was lost was enough to throw the fuel trims off. never had the code come on again

 

[Hutch89]

I have a '94 4.0 and it throws code 157, MAF low voltage, but i replaced it and the code is still being thrown. Ive replaced both O2 sensors and i pulled a vacuum on it and theres no leak. Any suggestions?

 

[ranger123456789]

p0174

I had the same issue. I replaced the O2 sensor (right side) and the EGR valve. Nothing worked. Cleaned MAF, then replaced the fuel fitler (make sure you get the tool), no change. Finally, I replaced the fuel pump, after testing it, I only had 20psi of fuel pressure, 50-60psi is required.

The idle and power issues went away. No more check engine light. There is a good video on how to make your own fuel psi tester here: http://youtu.be/poS2K9VdTR8

If I had to do it again, I would have tested for airleaks then fuel pressure first. I spent too much money on parts I didn't need.