Hi all. Made a post a few days ago, said it needed moderator approval... well 3 or 4 days later it's still not posted, so I'll rewrite this.

Recently bought a 2000 Ford Ranger XLT 4x4 3.0 FFV w/ 5-speed standard. Had a bad head gasket from the start, so changed those, as well as thermostat, coolant temp sensor, radiator, camshaft synchro, water pump, timing chain, intake gaskets, DPFE (the black plastic one with two hose ports, original cracked when removing), spark plugs and wires.

Didn't drive the truck a whole bunch before doing all this work, but didn't have any rich codes being thrown that I can recall.

Now, have a P0172, P0175, P1132, and P1152 being thrown.

P0172 - Fuel System Rich: Bank 1
P0175 - Fuel System Rich: Bank 2
P1132 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 1
P1152 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 2

Have checked for vacuum leaks with propane and carb cleaner, nothing. Checked fuel rail pressure, at idle it's about ~63psi, and after shutting down, doesn't drop below about 37psi. Tried the leaky fuel injector test, car doesn't start. Did notice that the MAF was reading something crazy, like 70g/sec so replaced the MAF and now it's down to around 3.5g/sec. Reset the computer after doing this... Nothing. Showing LTFT at -25%, really trying to compensate.

The cat does stink like sulphur sometimes, so I know that'll most likely need to be replaced.

It used to get about 240 miles per tank, 12mpg. Last night it left me stranded at only 201 miles after running out of fuel... So just at 10mpg.

Anyone have any suggestions? Could it be a bad/faulty alcohol sensor telling the computer that I'm always running E85 when I'm not?

EDIT: I'll also add that it idles rough and will die occasionally when I'm making a low-speed turn and have the clutch pressed in (engine dropping to idle). When I hit about 96mph, it'll lose power, almost like it's hitting a speed limiter, or not able to get enough fuel or air... Hard to say. Tried a new IAC from Advanced Auto, it just made the thing constantly idle at 3000rpm so put the original back on.

 

Codes

Freeze frame from when codes came up

Vacuum measured at manifold on drivers side front of engine

 

Vacuum is low, 14", but Colorado Springs shows 6,000ft elevation, I would expect 16" at least, 18-21" is expected at sea level to 2,000ft
Just looked it up and 5,000-6,000ft is 13-17" so I guess its OK
But man it must suck for power on any non-turbo engine at that elevation, lol, sorry

Yes, 1999/2000 Ranger 3.0l Flex fuels do have a fuel type(ethanol) sensor, you can get a "replicator" to replace it, turns it into Gas Only though
And it does read like you are running RICH so not simply a computer error

Couple of things to check with your OBD reader, if possible
Barometeric pressure, there is no Baro sensor but computer does calculate barometeric pressure based on other sensor inputs, like DPFE sensor
Google: colorado springs barometric pressure

Usually local airport or ?? will have that, it changes hourly but not by alot, see how they compare

And fuel type, there may be an ethanol % reading available

And/or air:fuel mix calculations
Gasoline is 14.7:1
E85 is 9.8:1

So a big difference, this might tell you if computer "thinks" its running higher ethanol mix, than it is

STFT is the calculated OPEN TIME for each fuel injector
+ STFT numbers means computer is Opening injectors longer because O2 sensor showed Lean(high oxygen)
- STFT numbers means computer is closing injectors sooner because O2 sensor showed Rich(low oxygen)
And it is a %
So if computer calculated open time of 100ms(milliseconds) then +2 STFT would mean injector was opened 102ms so 2% longer
And -2 STFT so 98ms would be 2% shorter open time than calculated


Yes, you can only use Motorcraft or Hitachi IAC Valves on Rangers, just a heads up, its not a stepper motor just a solenoid

 

RonD thanks for the reply.

Yeah, anything normally-aspirated here is a dog. Bleh!

I did however notice that the TPS is reporting 15% at idle with no foot on the gas, and only 85% at pedal-to-the-floor... Possible culprit?

I'll include two photos, one at idle, the other at ~3000rpm.



At idle (yes, it idles at 1000rpms...)

at 3000rpm

 

TPS reads correctly, those are "learned" % as well, generally 14-18% at idle is seen, and 85% at WOT(wide open throttle) is normal

Its a 5volt variable resistor sensor
Closed throttle should be .69-.99volt not 0volt, 0%
WOT should be 4.5v-4.7v so not 5v, 100%

Cold idle can be as much as 1,300rpm, but should drop as engine warms up
Warm idle should be 800rpms with automatic, 700rpm with manual

But Warmed up is when ECT sensor shows above 150degF

You said you replaced thermostat?
Did you use 190-195deg T-stat?
Thats spec, not 180deg


The O2 sensor voltage is looking better in the last set
.1v is Lean, high oxygen
.9v is Rich low oxygen

So sweet spot is .3-.4v


O2 sensors use chemical reaction to detect oxygen so they do run out of chemicals, upstream O2's usually last 100-150k miles
When they start to run out of chemicals they show a "false Lean" so computer will run engine RICHER than needed, BUT...........this won't show "rich codes" because computer doesn't "know" its running the engine too Rich, lol.


And just as a heads up, since vehicle is new to you
Some people think larger injectors will give more power, like larger JETS on a carb can
This is not the case, all you get with larger injectors are RICH CODES
Computer is programmed for injector size and fuel pressure, thats how it knows how much fuel will flow out of each injector when its opened for say 100ms
If larger injectors are installed it see O2s showing high volts so it goes into - STFT to correct it, and when it gets to -20 STFT you get Rich codes, and NOT more power, lol.

 

Makes sense. Won't touch the TPS.

Gotcha, thanks for that bit.

Yeah, I replaced it with a 192(?) degree thermostat. It was the hotter opening one that was offered at the auto-parts store.

At speed, when I check the on-the-fly O2 sensor voltage, they both will read around 0.88v. So based off your info, super rich. Interesting to know about the O2 sensors running out of chemicals... I'm almost certain these haven't ever been replaced.

Grr! I read one forum post here about a guy who had carbon-plugged port on his intake manifold (somewhere). Do you happen to know/remember that post? (I ask 'cause you responded in the thread, the seeming Ford Ranger resident scholar, lol)

Can't find anywhere that lists air/fuel ratio or alcohol % in my OBD2 scanner app. Don't know what else to check! With the two O2 codes appearing at the same time, I wouldn't think the O2 sensors are bad, but could it be...? Or a bad ECU/PCM?

 

Well darn. Pulled out the oscilloscope and looked at the waveform going to the injectors... had heard of a guy with a bad diode in the alternator that would still put out 14v into the system, although a very noisy signal that interfered with the injectors causing them to stay open longer. Well, alternator in or out, the waveform looked the same. I'm not sure where to go from here. I don't think the injectors on this car have been changed, but it'd probably be worth pulling one to check the model, just in case.

I don't know how, but could a clogged cat cause a rich condition through high back pressure??

 

You can test for back pressure with the vacuum gauge
Run engine at about 2,000rpm, just steady higher RPM and watch the gauge, it should stay steady, if it slowly starts to drop back pressure is building up in the exhaust
You can also "blip" the throttle, open it and let it snap closed, should see vacuum drop to 0-2" with throttle open then quickly come back to 14"(or higher), a slow return to 14" means blocked exhaust

Yes, 2 O2s failing at the same time are very long odds, but with no history you don't know that one failed a year ago, lol.
And in either case you WILL need to change them once you find the problem, rich running will ruin them

And what does Bank1 sensor2 show?
Thats the O2 after the Cat converter should be steady, .7-.8, "rich" but not really, the Cat converter should burn up most of the oxygen as is burns up emissions, so Downstream O2 should have a steady voltage and high for little oxygen seen


Just FYI, you can test for bad or leaking alternator diodes with volt meter set to AC Volts
Test battery with engine running, need to see UNDER .4vAC under 1/2 volt AC, if over then alternator is leaking AC into the system which can cause several issues

 

Just looking on line and there are ODB2 readers than can see fuel content, and maybe reset them, although the "replicator" may be the long term fix at this point

The Fuel sensor doesn't detect ethanol or gasoline, it detects WATER content, I didn't know this, lol

video here:

 

Good to know, I will check for a blocked cat with the vacuum gauge.

The downstream sensor does show .7-.8 volts... but I'm noticing that all three of them jump around seemingly randomly. It's hard to say with certainty where any one of them sits. Even when I look in a long-term graph, they're all over the place, up, down, you name it.

I pulled the upper intake off and used gasket sealer on the upper gasket... It actually idles much better now. I'm not convinced that my propane/carb cleaner vacuum test earlier really worked. The difference at idle is much better. Fuel trims are still showing -25% short term, so no dice with the mixture issue.

I've just purchased three new O2 sensors based on your input, which makes sense. This whole time I've assumed that they were both still good since the codes came up at the same time, but I have been getting one side rich much longer than the other side, so who knows? I'll change the three sensors and report back.

Thanks for the video! I want that guy's test setup, hah. If these O2 sensors don't fix it, I'll head to the pull-and-pay this week and pull one off a wrecked Ranger, just to see. Then I'll consider the eliminator product.

 

The upstream sensors should jump around fast, .2-.7 is normal after warm up, O2s need to be above 650degF to work, just FYI
Downstream will jump less
The computer is constantly changing injector open times, on purpose, it does go RICH every few seconds to feed the Cats extra unburned fuel to get them, and keep them, HOT
And it will suddenly go Lean to see if downstream O2 voltage drops to see if its working

Only 1999 and 2000 Ranger 3.0l flex fuel had the fuel sensors, so not easy to find and they sell for $550-$750 even used
Maybe try unplugging it, then do a computer reset
It will set a code for fuel sensor being unhooked, and I am hoping it defaults to gas only

Maybe see if the STFT starts to go to +15

The LTFT(long term fuel trims) stay around and are part of the base air:fuel calculation, so running at +15 STFT will slowly bring LTFT closer to 0
So if Bank 1 LTFT is -14, and STFT is -20 then thats actually -34 fuel trim, way Rich
So if you find and fix the problem you should start to see higher + STFT which will bring down the - LTFT closer to 0 each time you drive vehicle