4.0 running rich

[bulldawg1081]

hey guys what would cause a 91 4.o to run rich to the point that the raw gas fumes burn your eyes? and also what would make it sound like its running off of about 4 or 5 cylinders when you get over about 1400 rpm? thankyou for your help.

 

[4.0B2]

if you don't have fire to a couple cylinders, you're gonna have raw fuel...

verify spark on all cylinders to start. take the plugs out, look at 'em.
check your fuel pressure, make sure you don't have way to much pressure.

 

[bulldawg1081]

if you don't have fire to a couple cylinders, you're gonna have raw fuel...

verify spark on all cylinders to start. take the plugs out, look at 'em.
check your fuel pressure, make sure you don't have way to much pressure.

I guess I'm going to have to take it to a shop to have the fuel pressure tested since I don't have a way to do it, the spark plugs are fine other than having black soot on them...I forgot to mention that at an idle it will smooth up for a few seconds then start running rough again,I also noticed today when I was messing with the pressure switch on the AC that when I'd stick a paperclip in the plug the engine would start running different, not sure how all of that ties together

 

[4.0B2]

have an Harbor Freight close by? Or Nothern Tool? or one of those "Cheap Chinese made crap" Tool Stores? They are cheap and work pretty good.
http://www.harborfreight.com/fuel-injection-pump-tester-92699.html


however, after you saying it idles fine to begin with, I'm kinda doubting a fuel pressure issue. Idk tho.. wouldn't hurt to know.

Have you verified spark on all cylinders?

 

[bulldawg1081]

have an Harbor Freight close by? Or Nothern Tool? or one of those "Cheap Chinese made crap" Tool Stores? They are cheap and work pretty good.
http://www.harborfreight.com/fuel-injection-pump-tester-92699.html


however, after you saying it idles fine to begin with, I'm kinda doubting a fuel pressure issue. Idk tho.. wouldn't hurt to know.

Have you verified spark on all cylinders?

No sir, the coil pack could be going out, never thought of that...also could it be the tps or the o2 sensor? No cel on though. Yes, there's a harbor freight in amarillo TX, about 45 miles away

 

[4.0B2]

for the price of taking it to a shop...
you could fire the "parts shotgun" at it... just start putting stuff on it.

I'd clean the Mass Air Flow sensor. Check fuel filter, air filter, plugs, wires.
if there's no code, I'd doubt that it's the O2 sensors or a sensor needing replaced... but it's possible.

there's a way to use an ohms meter to check the TPS, you'd have to look it up though b/c I don't remember how it goes.

 

[RonD]

Check the fuel pressure regulator on the fuel rail, it has a vacuum line attached, remove the vacuum line and see if it has gas in it or smells of gas.
The rubber diaphragm in the regulator can leak as it gets older, this will then suck fuel into the intake via that vacuum line causing a rich condition.

 

[bulldawg1081]

Check the fuel pressure regulator on the fuel rail, it has a vacuum line attached, remove the vacuum line and see if it has gas in it or smells of gas.
The rubber diaphragm in the regulator can leak as it gets older, this will then suck fuel into the intake via that vacuum line causing a rich condition.

Thankyou Ron never thought of that either, next day off that will be the next thing I check