ive got a 94 f150 5.0. i got code 157 and 158 which was maf signal high or low. i replaced the MAF and it still runs rough i can unplug it and it smooths out. also what confuses me is with the maf plugged up and the motor running rough i can remove the upper intake hose from throttle body and the engine smooths out ive also noticed that the throttle body is sucking alot of air it feels like its going suck your hand in while idling is this normal?here is a list of what ive replaced so far

coolant temp sensor
thermostat
removed the cats
i tried an extra 02 sensor i had but no difference
cap/rotor/wires?plugs
MAF
air filter
upper and lower intake gaskets
and i went through the entire vacuum system lookin for leaks while i had the intake off and all is good

any help is appreciated im lost

 

That's a stumper. Does it do the same thing with the old MAF?

 

same thing with the old one too. i took loose all the conduit tonight and traced the wires from the maf plug back threw the harness to the computer and everything lookd fine.

i noticed when i take the hose off the throttle body and the idle starts smoothing out the check engine light comes on and this is while the maf still hookd up.

someone has removed the egr pipe that runs from the valve behind the intake down to the exhaust, the pipe on the valve thats supposed to run down to the exhaust pipe has been cut and crimped togethor. could this affect nething??

 

If you changed maf, possible loose or corroded terminal plug? Either that or the ecu is bad.

 

its got a new computer on it i had some fuel pump problems a while back had to replace it.

i got my multimeter out today and checked the wires on the maf plug i tested while it was plugged in and idling. heres what i got.

lt.blue/red- .43 volts cold then after it warmed up it stayed at around 1 to 1.2 volts.

tan/blue- read 0 every time

black/white- read 0 also

red- read around 14.5 volts

 

Anytime as sensor is replaced, the battery should be disconnected for 5 mins to clear & rebuild the KAM. Especially air intake related matters. Personally, I would restore full EGR function also if you want your ECU to be friends w/ you again. Are your just ignoring those error codes?

 

I'm not sure how that animal works. Red is fine, it's the power wire. Black/white is ground so that is good.

 

i unhooked the battery and left it off to clear the memory and i tested it again. this time i got code 158 and 334.

the 334 is high voltage to the egr valve what could b causing this?

 

It's probably stuck open.

 

sounds like you have a grounding issue....

on my friends 95 5.0L MAF when I unplug the MAF it dies at idle...

as his truck has an idling issue when warm...not cold or hot but in between