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running rich


sammyboy

New Member
Joined
Sep 1, 2015
Messages
3
Vehicle Year
1994
Transmission
Automatic
I have a 94 4.0 ranger. Idles rough, running rich. Had a mass air flow code, changed it same thing any ideas.
 
What is the code?
Codes rarely mean a part is bad

Engine is running rich?
No code, right
Just fuel rich smell, black exhaust?

On the fuel rail is the Fuel Pressure Regulator(FPR) passenger side front on intake.
It will have the Fuel Return line and a vacuum hose connected.
Engine off
Remove this vacuum line and check it for Fuel or fuel smell.
Inside FPR is a rubber diaphragm if it leaks fuel will be sucked into the intake via vacuum hose and cause Rich mix
 
Thanks I did that,no fuel smell. Also checked fuel psi and it was 35.
 
The code was 159 mass air above/below normal
 
159 has a couple of things that set it
key on, engine off self-test, if MAF voltage is greater than 0.7
Engine running self test, MAF voltage is not between .20 and 1.50 volts

All air coming into intake needs to pass thru the MAF sensor, all of it.
So a leak in the larger air tube will cause bad MAF data, or a vacuum leak.
 

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