2008 Ford Ranger Running Lean

[tah8436]

Have you checked the throttle body for cleanliness?

Yes, thanks for reminding me. I also cleaned the the TB when replacing the air filter. It was already pretty clean, so just a touch up.

 

[tah8436]

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.

No codes or engine issues outside of the long crank times. But I agree with D60, ideally it would be below 10.

 

[tah8436]

Probed the harness side of the CHT connector and got a consistent 5V with key on. I will update with fuel pressure readings soon.

 

[tah8436]

Ok, fuel pressure sits at 63psi at idle. Right within spec of 60-65psi.

However, immediately after turning the key off, pressure starts dropping and hits zero in less than a minute.

Bad fuel pump check valve? But I don’t understand why that would affect LTFT while driving.

 

[tah8436]

Posting this just in case it helps someone in the future. I pinched off the vapor purge valve line going to the manifold, to see if it was stuck open and allowing extra air past the MAF. No change to fuel trims.

I also got Forscan and monitored CHT, which reads as expected, starting at ambient temp and climbing to about 180F after a 15 minute drive.

I still don’t understand how a bad check valve would hurt LTFT even when cruising