So I just bought a 2001 3.0 v6 ffv ranger (My first ranger), I discovered it runs super rich, alot of soot out of exhaust on cold start, currently giving me 7 MPG!!!! conected obd reader and it has only 2 codes:

P2196 AND P2198 : HEATED OXYGEN SENSORS BANK 1 AND 2 STUCK RICH


I discovered on cold starts it adjusts correctly fuel trim long and short (closed loop) but imidiently starts pulling fuel out about 10 seconds in until it gets to -28% and PCM enters open loop.


Seems like somehow fuel is getting dumped into the cilinder or something... any ideas what it could be? i already changed the 02 sensors and it didnt fix it, maf looks ok, IAC is ok, new pcv valve, new plugs... already checked for obvious things like fuses, etc.

Can the EGR valve have something to do? or the EVAP system in general?

Vacuum leaks would make it lean if im correct?


funny thing is it runs good, just super rich and the 7 MPG is killing me... please help.

 

Welcome to the forum

I would first test fuel pressure, 60psi is expected, pump is capable of 80+ psi, pressure regulator is in the gas tank
I doubt it's the issue since cold running seems OK
There is no fuel pressure sensor, computer assumes 60psi +/-5psi

Some people think injectors are like Jets in a carb, they are not
So they put in larger injectors to get more power, and what they end up with is less power and RICH codes
The Computer(PCM) is programmed with injector size, so it knows exactly how much fuel is released at 60psi when it opens an injector for 100ms(milliseconds)
That's what the Fuel trims represent
0 STFT is computers calculated open time for each injector, based on RPMs, throttle position and sensor data, assumes fixed fuel pressure and injector size
+10 STFT means computer is opening injector 10% longer than it calculated based on O2 sensor feedback
-10 STFT means computer is closing injector 10% sooner than it calculated based on O2 sensor feedback

Having both banks of the V6 engine Rich means it's unlikely to be 1 bad injector, that would only effect that one bank, possible just a long shot
Wrong injectors size would be more likely

And then you have computer issue
On cold start the computer doesn't do air/fuel calculations, because O2 sensors need to be above 650degF to work, computer is in open loop so uses air/fuel mixes from a table in memory
The fact it runs OK cold tends to point to fuel pressure and injector size being correct

After O2s are heated up and working computer then takes over and does air/fuel calculations on the fly, Closed Loop
And this is where the problems start
As said computer "assumes" fuel pressure and injector size, it has no way to tell if those are wrong
It also has no "test" for O2 sensors to see if they are accurate but both O2s on each bank failing at the same time are long shots
MAF and other sensors can cause air/fuel mix issues, but almost always going with Lean codes, not Rich

So if fuel pressure is OK, 55-65psi
And fuel injectors are correct, don't look new
Then its most likely a computer issue

 

I wonder if an injector could be stuck open. https://www.ranger-forums.com/member...2/#post2201856 Here is how I test my injectors and clean them. Not the most high tech but works for me.

I see you just bought this truck. Nobody trades off a good truck that is not at least lacking in maintenance. I always expect to spend several hundred just in the basic of tune up, brakes, suspension... I have fixed several issues and it will keep you from going in circles. I dont even try trouble shooting until I know that consumable parts are replaced or at least in great shape. Always start with a complete tune up using top quality parts. O2 sensors and Throttle Position Sensors hardly are ever replaced and they just wear out. Other sensors may just need a good cleaning. How are your vacuum hoses? Are they brittle, cracked and routed properly? Any air that is getting into the system thru leaks is unmetered air and the computer cant react to that in most cases. Any gunk build up from the EGR? Ports clogged? I have seen carbon build up so bad in an Intake system I am surprised the trucks have even run.

 

I recently purchased a 99 with a 3.0 in it. I like you noticed a very rich exhaust smell walking around the truck during initial exam. Purchased truck as it was in great shape and realized there are no cats on the exhaust. I get around 270 on a tank which i feel is not good. However i bought the truck as a backup to my motorcycles that i ride to work unless it’s raining. A tank lasts me around 2 months so not really worried about it but would like to have it fixed but afraid not cost effective.

 

Yes, no Cats would cause Richer running, not because Cats are gone specifically, but because the O2 sensor after the Cats is either disconnected or can't work

The computer feeds a shot of extra gas into the exhaust every now and then to keep the Cats hot enough to work, this is based on that O2 sensor voltage/feedback
Since it not working computer runs the engine Richer almost all the time hoping to get it working
There is no work around to "fake out" computer on this sensors feedback, it not consistent voltage, computer runs exhaust lean then rich to test if that sensor and Cats are working so................

 

You should be getting a code of some sort basically pointing to Sensor or Catalytic Converter. The computer compares the differences of the exhaust before the converter and after the converter. With no converter the O2 sensors are reading the exact same fumes and computer should recognize and throw a code.

It has been a long time but I was around a car that was made before converter were installed. Like a late model 60s truck. There is a difference in the smell of exhaust fumes between trucks with converters and non converters. Took me a few moments to realize why smell was different or maybe a friend of mine pointed it out to me why pre cat trucks smell different.

 

One thing you need to check is the fuel pressure dampener on the fuel rail. Pull the vacuum line off of the end. If there's fuel in the vacuum line, or fuel spits out of the damper when you remove the hose, the dampener is leaking. When that happens, the vacuum hose sucks the extra fuel into the intake, which the computer is not accounting for. Causes a rich condition, which in turn causes the computer to subtract fuel. May not be the cause, but it is worth checking. I had the one on my 2002 Ranger fail, and it caused all sorts of issues for me.

 

I already checked fuel rail dampener and no fuel came out, changed fuel filter, new EGR valve, removed injectors and test them and still throws same codes.. MAF shows 4.48 g/sec flow rate on idle is this normal? also noticed lower o2 sensor doesent show voltage on OBD2 is this a problem? or normal? i couldt accurately check fuel pressure ( cheap chinese gauge) so im considering just replacing the fuel pump, but if it would be a fuel pressure issue wouldnt it throw a high fuel rail pressure code?

Thanks for the help!

 

Rangers never had fuel pressure sensor, so incorrect pressure would have Lean or Rich codes

O2 sensors need to be heated above 650degF to work, and they generate their own voltage after they are warmed up, so they would show no voltage at cold start, would have to wait for 3 or 4 minutes of run time at least

Rule of thumb for MAF grams per second reading is 1 gram per Liter of displacement at 500RPMs, so 3 liter engine should show approx. 3g/sec at 500RPMs
So RPMs are important, most WARM engine idles are 800RPMs, so would expect up to 3.8g/sec, 4.48g/sec seems high if engine was fully warmed up and idling at 800RPMs
And that would cause Rich codes since MAF is over reporting air weight, telling computer the air is heavier than it really is


Computer already knows its operating a 3 Liter engine, so it already knows EXACTLY how much air is coming in at any RPM, its just Math
What it doesn't know is how much that air WEIGHS per liter, that's what MAF("mass" air flow) sensor is for, it tells computer the weight of the in coming air

Gasoline engines used 14.7 to 1 air fuel ratio, and that's a WEIGHT RATIO not volume
14.7 pounds of air to 1 pound of gasoline
OR
14.7 grams of air to 1 gram of gasoline

Air weight changes quite alot when air is colder or warmer, or if you are driving at sea level or in Denver at 5,000ft elevation

So if MAF is reporting heavier air then computer adds the extra fuel needed for the heavier air
Then O2 sensors tell computer that there is too much fuel(low oxygen) in exhaust so computer reduces the fuel flow out of injectors, if computer has to reduce the fuel flow by more than 20% it sets a Rich code
Rich code tells the driver there is a calculation error in the computer, which is usually caused by sensor data or "assumed data", in this case fuel pressure since computer is programmed for expected pressure, and no sensor to correct for that