Hey guys, on my '02 Ranger with 115k miles I've started receiving codes that both banks are running lean. My understanding is that this basically means either I have a vacuum leak or a problem with my fuel system, or a bad/dirty MAF. My fuel filter is only like a year old so I doubt it's that, but it could be my fuel pump I suppose. In looking around I found that you can usually narrow it down by watching the fuel trim. My long term is usually around +25 with short term around 5-10 while idling, but if I start driving they usually average down to zero. My understanding is that generally means fuel is fine (as the problem would be worse when driving than idling if it was a fuel delivery issue, right?). Would this also likely rule out the MAF? I would think the problem would be more consistent if it's the MAF. That leaves me with vacuum leak.

My PCV valve is only ~2 years (and 10k miles) old. I checked the hose/elbow for it and it seems fine, and I replaced the grommet as it was a bit loose (but that didn't solve my issue). The hose to the brake booster and the breather to the intake also seem fine, and the main intake hose (that the MAF is attached to) also looks fine. There's a hose going from the throttle to the EVAP which seems a bit suspect (photo attached), so I may look at replacing that... could it be the EVAP canister itself?

I also have noticed I've got a coolant leak coming from what appears to be the upper rear of the engine block (above the spark plugs). Does this point to a bad intake gasket?

Finally, I replaced the timing cover gasket about 2 months ago... would a bad seal on that cause this issue? I would think if so I would have seen the problem sooner than a week ago.

 

02 Sensors, there is two up front and 2 down below......i have the 03 v6 it has the plastic intake with O rings sealing it to the intake manifold.....check seals and O2s in header pipe

 

 

yes wild for both if they done over 100,000 miles replace .. 03 3.0 does not have EGR....i think your MAF could be the problem you can test it with ohm meter


On a 2003 Ranger the IAT is in with the MAF sensor, combo unit.
The two outside wires of the 6 wires are for the IAT sensor.
Inside 4 wires are for the MAF sensor.

Remove the MAF connector, key off
Set OHM Meter to 100k or so
Touch probes to the 2 outside connections on the MAF sensor.
At 50degf you should see about 60.0k ohms
At 60degF you should see about 45.0k ohms
At 70degF you should see about 35.0k ohms

So the warmer it gets the lower the ohms
If you can, blow some warm air thru sensor, hair drier but not too hot, to see if ohms are changing.

 

Lean both banks is usually a vacuum leak post maf. If your also leaking coolant I'd look into an intake manifold leak. If you have an obd adapter and torque software you can log the wave form of your o2 sensors and pretty quickly detect a lazy sensor.

 

Hey guys thanks for the posts. Due to the weather here in CO I put off looking into this until recently. I built a paint can smoke machine based on instructions online and hooked it up to the brake booster line. I didn't see any smoke come from anywhere, but I could hear an audible hissing coming from the engine. I couldn't pinpoint it but if I climbed under the truck it sounded like it was coming from the driver side somewhere around the middle of the block. AFAIK the main gaskets here are head gasket, intake gasket, and timing cover gasket. I recently replaced the timing cover gasket so I worried I botched the job but I don't think there should be any vacuum passages that rely on that gasket. Similarly, if it was a head gasket, I would think I'd only get a code on one bank instead of both. Does that sound right? If so, I'm thinking it probably is the intake gasket, I just want to be pretty sure before I undertake the job. Is there anything else in the region it could be?

Thanks for the help!

 

Both banks lean means Computers calculations for injector Open Time is low, so computer is opening injectors longer to balance Oxygen Levels in exhaust, O2 sensors
STFT(short term fuel trim):
+1 is 1% longer open time for fuel injector
+5 is 5% longer
+10 is 10% longer

-10 to +10 are fairly normal ranges as engine and systems get older

At +15 or so computer will set Lean code, to let driver know its calculations are off

Computer uses Tables in Memory for engine size, RPM, Throttle Position to set BASE air fuel mix.
i.e. a 3 LITER engine, at 1,500rpm and 1/4 throttle will suck in XXX liters of air per minute, EXACTLY, its just math.
Computer uses MAF sensor to fine tune the Mix and also air temp, this tells computer how much each LITER of air WEIGHS, at vehicles elevation and outside temp.

Gasoline Air:fuel ratio is 14.7:1, and thats a weight ratio
14.7 POUNDS of air to 1 POUND of gasoline
14.7 grams of air to 1 gram of gasoline
WEIGHT ratio
(so there was NEVER a 200mpg carb, and pre-vaporizers can never benefit you, lol)
A liter of air weighs more at sea level than at 4,000ft elevation.
Colder air is heavier than warmer air, i.e. "hot air rises"
So MAF and IAT sensors compensate for elevation and air temp.


For both banks(V6, V8) to show lean then yes it is unlikely to be O2 sensor problem, but just FYI, upstream O2 sensors with over 100k miles lower MPG slightly, so changing front two O2 sensors can pay for themselves over the next 100k miles.

Could be MAF sensor, probably not IAT sensor, but not off the table.
Vacuum leak is really the most common issue.
Simple test
Warn up engine to operating temp, let it idle
Open the hood and unplug the IAC Valve
IAC Valve will close and engine RPMs will drop to 500 or engine may even stall, either is GOOD it means no vacuum leaks

If RPMs stay high then you have a leak

Leak would be in upper intake or its hoses, lower intake leaks usually only effect 1 bank

If no leak, i.e. RPMs drop in test, then check fuel pressure, 2002 should be 50psi or higher.
Run some injector cleaner in the gas tank, dirty injectors will drip fuel at low RPMs so poor mix that doesn't effect higher RPMs

 

I'm getting +25-+30% STFT+LTFT at idle, but under load it seems to about zero out.

I'll check out the IAC if you think the lower manifold is unlikely. Thanks for the feedback!

 

Lower intake would effect one bank/cylinder, not both

Switch MAF readings to gm/sec, grams per second

At 700-800rpms you should see "displacement" of engine
So 4.0l engine would read about 4, +/- .2
3.0l = 3
2.3l = 2.3
5.0l = 5

 

Being that I'm at about 6000 feet, and thus the air is about 15% thinner here, would I expect my 3.0l to be more like 2.5-2.6?

 

Yes, MAF reads the WEIGHT of the air so at 6,000ft it would weigh less, but don't know the calculation for that.
15% less sounds right though