2008 Ford Ranger Running Lean

[tah8436]

2008 Ford Ranger 2.3 Duratec

Symptoms: I noticed my LTFT was 16% at idle and 12% with throttle applied. My radiator fan runs immediately, even when cold starting. Lastly, when warm (30-120 mins after driving), I get long crank times before it starts. This is not an issue on cold or hot starts.

I did not suspect a vacuum leak, since LTFT stays high even under throttle. Cleaned MAF sensor, no change. Readings look ok to me (2.5 g/s at hot idle). Replaced air filter w/ Bosch workshop filter. Replaced cylinder head temp sensor with Standard Motor Products part. The old one had a crack in the plastic body, but could have been from when I was removing it.

After cleaning MAF, new filter, and new CHT sensor, no change to symptoms.

What should my next step be? I’m getting no codes, but fed up with the higher-than-ideal fuel trims.

Also, o2 sensors are reading as expected.

 

[ripcord]

I believe an 08 Ranger would have a conventional clutch and belt driven fan, not an electric one? Your fan clutch may have seized up which is not unusual with a high mileage rig. When they do that they can be quite loud. If you determine this is the case, I would get a new standard duty (not heavy duty) fan clutch unless you sometimes tow heavy and run hot. A heavy duty clutch fan is louder, spins the fan more than necessary and wastes gas.

How do your plugs look?

https://giooomxdw.blob.core.windows.net/spark-plug-spark-color.html

 

[JavierH19]

Radiator fan runs immediately? i wonder what the temperature sensor that is used by the computer to run the math on the air fuel mix is reading. It's rarely the same one as the one on the dash but i think it uses data from the other in its math but usually refers to one as the main. I believe most everything has two being one for the coolant and one for the head or two for both heads.

 

[tah8436]

I believe an 08 Ranger would have a conventional clutch and belt driven fan, not an electric one? Your fan clutch may have seized up which is not unusual with a high mileage rig. When they do that they can be quite loud. If you determine this is the case, I would get a new standard duty (not heavy duty) fan clutch unless you sometimes tow heavy and run hot. A heavy duty clutch fan is louder, spins the fan more than necessary and wastes gas.

How do your plugs look?

https://giooomxdw.blob.core.windows.net/spark-plug-spark-color.html

Thanks for responding. I believe my specific Ranger (2.3L with A/C) used an electric fan. My plugs look ok, they’re about 30k miles old.

Could my fuel pump be getting weak, causing the high positive fuel trims?

 

[tah8436]

Radiator fan runs immediately? i wonder what the temperature sensor that is used by the computer to run the math on the air fuel mix is reading. It's rarely the same one as the one on the dash but i think it uses data from the other in its math but usually refers to one as the main. I believe most everything has two being one for the coolant and one for the head or two for both heads.

The way I understand it, the cylinder head temp sensor commands the cooling fan and communicates engine temp to the ECU, whereas the other coolant sensor just sends the dash temp gauge a reading.

 

[JavierH19]

The way I understand it, the cylinder head temp sensor commands the cooling fan and communicates engine temp to the ECU, whereas the other coolant sensor just sends the dash temp gauge a reading.

Yes but one if not both can be used by the computer to determine how much fuel to inject either more or less depending on what it's calculating

 

[tah8436]

Yes but one if not both can be used by the computer to determine how much fuel to inject either more or less depending on what it's calculating

I have the Motorcraft part for the other sensor. I’ll try replacing that too, giving me new sensors on both sides.

 

[ripcord]

Thanks for responding. I believe my specific Ranger (2.3L with A/C) used an electric fan. My plugs look ok, they’re about 30k miles old.

Could my fuel pump be getting weak, causing the high positive fuel trims?

I could have sworn those all had mechanical fans. Is the electric fan an additional one mounted on the front of the condenser behind the grill with a conventional fan mounted to the front of the engine?

If you suspect a weak fuel pump, you should test the fuel pressure.

 

[tah8436]

I could have sworn those all had mechanical fans. Is the electric fan an additional one mounted on the front of the condenser behind the grill with a conventional fan mounted to the front of the engine?

If you suspect a weak fuel pump, you should test the fuel pressure.

Ah, you are correct, I see a second fan back there. Thanks for the tip on the clutch. Harbor freight had just closed when I tried to grab a fuel pressure gauge, so I’m planning to stop there tomorrow.

 

[ripcord]

Ah, you are correct, I see a second fan back there. Thanks for the tip on the clutch. Harbor freight had just closed when I tried to grab a fuel pressure gauge, so I’m planning to stop there tomorrow.

OK. So the electric one should cycle on when the AC is in use.

I'm not 100% sure your engine has a schrader valve on the fuel rail to easily check pressure. If not, you may need to 'T' into the fuel line to measure it. I have that Harbor Freight fuel pressure kit and it has an adapter for doing that, but you might need to buy an extra length of fuel line and some other bobs and bits to rig it up.

 

[Lubener]

2008 Ford Ranger 2.3 Duratec

Symptoms: I noticed my LTFT was 16% at idle and 12% with throttle applied. My radiator fan runs immediately, even when cold starting. Lastly, when warm (30-120 mins after driving), I get long crank times before it starts. This is not an issue on cold or hot starts.

I did not suspect a vacuum leak, since LTFT stays high even under throttle. Cleaned MAF sensor, no change. Readings look ok to me (2.5 g/s at hot idle). Replaced air filter w/ Bosch workshop filter. Replaced cylinder head temp sensor with Standard Motor Products part. The old one had a crack in the plastic body, but could have been from when I was removing it.

After cleaning MAF, new filter, and new CHT sensor, no change to symptoms.

What should my next step be? I’m getting no codes, but fed up with the higher-than-ideal fuel trims.

Also, o2 sensors are reading as expected.

A problem with the coolant temperature sensor feeding the computer (not the dash gauge) can cause your problem and make the cooling fan to run when it shouldn't.

 

[tah8436]

A problem with the coolant temperature sensor feeding the computer (not the dash gauge) can cause your problem and make the cooling fan to run when it shouldn't.

I agree. That’s the one I already replaced, but unfortunately did not fix the issue.

 

[tah8436]

OK. So the electric one should cycle on when the AC is in use.

I'm not 100% sure your engine has a schrader valve on the fuel rail to easily check pressure. If not, you may need to 'T' into the fuel line to measure it. I have that Harbor Freight fuel pressure kit and it has an adapter for doing that, but you might need to buy an extra length of fuel line and some other bobs and bits to rig it up.

There’s a schrader right up front on the rail, so I’m hoping that part will be easy enough. I’ve seen that I might need to cycle the key a few times to get an accurate KOEO reading. I’m going to try 3-4 turns of the key.

 

[D60]

So what is water temp/CHT reading?

If it's not getting a reading or it's the default -44 then it'll kick on any fans it can and dump a ton of fuel. This also causes easy cold starts and difficult hot starts.

 

[tah8436]

I assume my coolant temp reading comes from the sender that supplies the gauge. It reads as expected, increasing from cold up to 190ish when hot. I don’t think my scan tool can read the CHT, I don’t see that as an option.

 

[D60]

I assume my coolant temp reading comes from the sender that supplies the gauge. It reads as expected, increasing from cold up to 190ish when hot. I don’t think my scan tool can read the CHT, I don’t see that as an option.

Is this a generic reader? There's gotta be a PID for engine or water temp somewhere. I know my Otofix could pull up CHT on an '06 Expy 5.4 (and the results were really weird)

D

Post in thread 'Ford's CHT (cylinder head temp) sensor'

Sep 4, 2025

It's dry, I've replaced it before.

Ford did some annoying stuff on the modulars like moving the sensor around a bit and I think some of the earlier years (ie bubble bodies) had two: one for PCM, one for the gauge. But AFAIK '06 just used the CHT here for both engine mgmt and the gauge.

I think I'll fire up my wife's '08 F150 and see if the 0.5V behavior occurs. Curious to know.

• D60

• 

 

[tah8436]

Is this a generic reader? There's gotta be a PID for engine or water temp somewhere. I know my Otofix could pull up CHT on an '06 Expy 5.4 (and the results were really weird)

D

Post in thread 'Ford's CHT (cylinder head temp) sensor'

Sep 4, 2025

It's dry, I've replaced it before.

Ford did some annoying stuff on the modulars like moving the sensor around a bit and I think some of the earlier years (ie bubble bodies) had two: one for PCM, one for the gauge. But AFAIK '06 just used the CHT here for both engine mgmt and the gauge.

I think I'll fire up my wife's '08 F150 and see if the 0.5V behavior occurs. Curious to know.

• D60

• 

yeah, it's a cheap generic reader. I'm looking into better scanners or Forscan right now. Interesting thread there, thanks. I guess something I can do right now is test if the harness side of the connector is getting 5V with the key on?

 

[goofy]

Have you checked the throttle body for cleanliness?

 

[mk378]

The electric fan may start rather promptly if the A/C compressor is engaged with the vehicle not moving. This includes the defrost setting.

Yes you need something that can read live data to confirm temperature sensor readings.

I think up to 20% LTFT is acceptable, if you're not getting runnability problems or codes.

 

[D60]

I think up to 20% LTFT is acceptable, if you're not getting runnability problems or codes.

10, really