99.2.5: Runs rough-Where to start?

[Leigh]

(1) The last few days began to smell fuel "odor" near bed area.

(2) Today, noted black, sooty water from exhaust pipe.

(3) Did a "Key-On" / Engine-OFF diagnostic.= 4 Results:

P1506: Idle Air Control Overspeed. Error
.
P0453: EVAP Emission Control System Pres Sensor High.

P0302: Cylinder #2 Misfire Detected.

P0304: Cylinder #4 Misfire Detected.

ADDITIONAL INFO:

Two days ago, the fuel gauge "dropped" to a reading of 1/2 tank, with a near full tank, then rapidly to "0". (I thought it might be the Anti Slosh Module, but with all this other "stuff", I'm not sure?)

I replaced the Fuel-pump with a new Delphi unit, about 6 months ago, & Rail pressure was well within spec., & Truck ran fine.

Truck wont run long enough, or "smooth enough to do a MIL / Engine running diagnostic.

 

[RonD]

No matter what they add to the outside of a gasoline engine it is still just a gasoline engine

And while computers make them 500% more reliable than the "good ol' days" they all still run because of 3 things
1. Spark, at the right time
2. Fuel, in the correct mix with air
3. Compression, above 120psi

Computer codes are "nice" but a vehicle computer is not smart, a vending machine from the 1980's was "smarter"
But they do have their uses

The misfire codes mean you need to pull out a spark plug from #2 and #4 and see what the tips tell you.
I would also pull spark plug from #1 to use as comparison.

Google: spark plug reading chart

Lots of images of what different tips mean

See if you are running Rich or Lean
With misfires you usually also get Lean code, because of the extra air(Oxygen) in the exhaust, but you are not getting that.
And misfire also means raw gasoline is going into the exhaust, it wasn't burned, so raw gas smell from exhaust, and black sooty look from partial burning of raw fuel in Cat Converter

The IAC Valve overspeed can be from the misfires, since engine is struggling to idle, computer is opening IAC Valve more than it thinks it should to get, for example 700rpm, so it says IAC valve is open farther, "overspeed" than it should be.

So diagnose misfires first.

Since you are smelling gasoline near the tank you could have a pressure leak in the system, but could also be exhaust leak near there and you are smelling raw fuel in exhaust.
1999 Ranger should have 65psi fuel pressure at the fuel injectors, there is a test port on the injector rail.
You can borrow or rent a fuel pressure tester from most auto parts stores.
Pressure should be 60-70psi with engine running.
After engine is shut off pressure should hold above 45psi for a few MONTHS, not minutes, hours or days, months.

 

[tomw]

I think I just read this post ... or one like it.

I'd check the fuel pressure regulator. If it fails, you'll get a crappy idle, and fuel mileage will drop in half. Take a whiff test of the vacuum line on the regulator and if it smells of fuel, likely diaphragm failure, requiring a replacement regulator.
tom

 

[Leigh]

I think I just read this post ... or one like it.

I'd check the fuel pressure regulator. If it fails, you'll get a crappy idle, and fuel mileage will drop in half. Take a whiff test of the vacuum line on the regulator and if it smells of fuel, likely diaphragm failure, requiring a replacement regulator.
tom

Thanks,
Where is the Fuel Pressure Regulator located---, in the engine compartment, or on the Fuel-pump?

Leigh

 

[RonD]

1999 Ranger 2.5l uses a Returnless fuel system, 65psi pressure, so it won't have a Fuel Pressure Regulator like previous years.

After looking at #2 and #4 spark plugs to ID misfire cause, also try unplugging the MAF sensor and then starting the engine, see if it runs better, could be MAF sensor is dirty or failing