1994 Ford F-150 5.0l
OK so I got this mass airflow code 157
I checked the mass air flow sensor with multimeter and the maf voltage test good. MAF out wire to computer is good.
I have no power, engine spitting, fume level is high and getting the maf code 157
not sure what my next move should be.
anyone had this problem?

 

Forgive me if mistaken but that means the reading was too low

does your tp sensor have any wiring issues amd is your iac working and clean? Filter? Clean?

use maf sensor cleaner on the elements? I had debris on mine

 

Code 157 (Stored Code): MAF sensor went below 0.4 volts during the last 80 warm-up cycles.

This is a code displayed in Stored Codes/Continuous Memory. The most common cause of this error is a bad connection to the MAF. After cleaning and verifying the connections, as well as MAF output, it is highly suggested you then clear the codes stored in the computer's memory. Drive the truck, then re-run the KOEO tests and Stored Code display.

 

I cleared codes. Not getting 157 code anymore so it must of been an old code.
MAF Is clean voltages check out
IAC cleaned and idles fine
TPS tested and voltages test fine
drove it down the rode after clearing codes and still runs like a piece No code thrown after the drive.

 

Check the fuel pressure at idle (30-32 PSI) , then remove the vacuum hose to the fuel pressure regulator. The pressure should increase to ~40 PSI or greater. While the vacuum line is off inspect the FPR vacuum port for signs of fuel. Very common issue is a leaking diaphragm inside the fuel pressure regulator. If that all checks out good, re-install the vacuum hose then blip the throttle. The pressure should rise from ~30-32 to ~40 PSI.

Are there any exhaust leaks before the O2 sensor(s)? If there are the computer will add fuel thinking the mixture is lean.

How old are the spark plugs, wires, cap/rotor?

How old is the air filter? and fuel filter?

 

fuel pressure at 30 psi. Remove FPR no change in pressure. No fuel coming out of FPR
Need a FPR?
fuel pressure actually drops a little when blipping throttle
Fuel filter is new

truck idles smooth and does not have a miss in it that I would relate to plugs firing.

 

Good be a bad regulator or plugged fuel filter or a weak pump. If the truck has dual tanks test the pressure using each one. Simple and easy is replace the fuel filter.

Does the truck have dual tanks? If so, do you notice a difference in MPGs between the two? Does one tank seem to fill itself?


Under load aged ignition components will rear their ugly head. How old/miles are the ignition components?

 

not just ate either. Bent and loose plug and cap connections from improperly putting on and taking off wires will decrease contact area, increasing resistance, potentially cause gaps, which spark now loses energy to jump but with time and no grease, the gap causes air nearby to ionize and can degrade things…and can also leave a pleasant surprise by slowly zapping away the tower/plug end to be smaller.. and also etch marks in them which are nit conductive and impossible to clean

carbin tracking is fun, plugs are shot if you see or period and it happens way too ofte. Carbon gets etched in porcelain and wire ends of plugs, these tracks are deep and don’t help conductive paths they burn into.

use dielectric grease for ignition connections use plug wire tools for wires, route wires away from engine control wiring, short as possible to and from cap and plugs, use quality wires, don’t let wires lay on each other. Use separaters If need. Avoid aluminum maintenance parts, get brass plated or just brass parts, use proper gaps, torques, and just ensure proper connections on all parts. I’ve seen new ignition parts die quickly from “small” issues lol. Ones that make it to old age usually means they were doing something right

oh and of course verify timing

 

Just replaced FPR , same results.
the fuel filters is not old month or two and the line is not stopped up as I tested the line with air.
Even with the new FPR fuel pressure drops when revving the engine. From 30 to 25ish. Maybe lower.
im starting to lean to weak fuel pump. But then why would fuel consumption increase. Just hate to bust out another dollar for nothing.

this is my brothers truck and he is in the hospital, I’m trying to get it going for him when he gets out. Probably going to be a few weeks

dual tank - yes it is a duel tank, but the front tank has a know Bad pump. So I can’t use that for testing

we did replace the rear fuel pump about a year ago.

 

does the front take slowly fill with gas

 

Sounds like you need two new pumps to me. Pressure dropping when blipping the throttle is the key. Under actual load, I bet it drops below 20 psi.

 

Arounagirl negative, Don’t have that problem thanks.

I am going to put a nee pump on today. See what happens. Thanks

 

Turned out to be fuel pump. Holds pressure of at least 35 lbs.
thanks for everyone’s help.