5.0 running very rich

[Hill185]

For sometime, my car has been running very rich with loss of power, stumbling, and misfires.

I have replaced the following,

-Upper plenum gasket
-PCV valve and screen
-endless vacuum lines
-MAP sensor
-throttle position sensor
-EGR valve
-fuel pressure regulator
-spark plugs and tune up
-fuel pump
-fuel filter
-smog/air pump
-IAC valve
(added fuel injector cleaner to gas as well)

I recently did a smoke test to look for vacuum leaks. only leak I observed was smoke emanating from a metal pipe that crossed over the transmission bell behind the back of engine, but I think that’s the air injection pipe that sends emissions to the cats so I don’t think that’s affecting the operation of the motor (pic below). No other leaks observed.

OBD I reader is giving me code ‘32’ which is a bad EGR I believe (pic below). But that was replaced with no improvement, unless the new EGR is bad?

i’m thinking maybe bad fuel injectors? I’m running out of ideas. Thanks for any pointers .

[WagonMan]

Bad Oxygen sensors or wiring,(cut wires). Check grounds on back of engine by bell housing. WagonMan

[gadget73]

32 is an EGR position sensor thing, usually won't cause any grief other than the EGR won't function with the sensor out of range. Fuel mix won't be affected.


agree on checking that wire at the back of the intake, its the sensor ground and if thats off it skews things. Its an orange wire that comes out of the O2 sensor harness. Some use a stud at the rear of the lower intake, some bolt to the back of the head. doesn't matter so long as its connected.

[Hill185]

Thanks guys, I’ll replace the 02s and look around for wiring ground issues. (Sorry for the double post if an admin could delete the duplicate)

[Hill185]

Looks like the ground wire is intact. As seen in the photo. I’ll order 02 sensors to see if that helps. Those don’t look fun taking out lol.
you guys recommend taking those out from the engine bay or from underneath?

[sly]

Try unplugging the vacuum line on the EGR valve and plugging the line. If it runs better, it could be the EVR (the solenoid that regulates the vacuum to the EGR).

[Hill185]

Thx Sly, I’ll give that a shot as well

[Hill185]

I unplugged EGR vacuum line and plugged it with no change I even bought a whole new EGR also with no change.

I did buy two new oxygen sensors, but I could not get the old ones off so I cleaned the old ones, again with no change.

**Is it possible the new aftermarket MAP sensor is no good?

** I have not changed the coolant temp sensor on the manifold, not sure if that would cause it to run extremely lean?

** just to clarify, this large air/vac that runs on passenger side which turns into metal pipe behind the engine near the tranny bell housing failed the smoke test near the bell housing (rotted metal). I included a pic and its highlighted in red.

I must admit, this has been driving me nuts lol.

Thanks guys for all the help. I used to be the advocate for the 5.0 over the 5.8 not sure I can do that anymore lol

[friskyfrankie]

Before making yourself nuts you do need to fix any and all vac leaks. Then go from there.....

[Hill185]

Yes, took the upper intake off, changed all those vac lines, and many more. I did a smoke test to try and see if that could narrow down any further leaks. As a result of the smoke test, only the metal tube behind the engine, as mentioned above, showed a leak .

[friskyfrankie]

Is it the type of environment where you can replace the metal pipe with a silicon heat resistant vac hose?

[Hill185]

Hm. I suppose it could be done. The metal pipe plugs into the back of the drivers side head. I’m assuming it’s an air injection pipe for the crank case??

[gadget73]

normally I've just cut those things off, flipped the plates over and bolted it back on. Not much chance of getting a plug into those things most of the time, they are well packed with carbon

also unlikely to be seeing intake smoke out of it since its on the exhaust side of the head. If there was a leak you'd hear a sound like an exhaust leak. What you might see back there which is connected to the intake is the PCV valve though. Leaks around the grommet will appear rear center of the engine.

If the smog pump controls were messed up and pumping air into the head all the time it will read lean on the O2 sensors and run rich as a result. Pull the belt off the smog pump and see if anything changes.


thats not for the crankcase. its air injection for the exhaust. For the first few minutes it pumps air into the heads which comes out through a small hole in the exhaust port to help warm the converters up quicker.