I have a 1990 F-150 with a 4.9 inline 6. The check engine light is on and the snap-on scanner returns these codes:

24 - Air Temp (ACT/VAT) Out of Range
41 - EGO (Ho2s) Not Swithing Rich & Lean
and Fix Last code is
18 No Tach Input pr spout CKT Open

I'm sure there are various cures to these codes but where should I start? What are all the acronyms?

Thanks for any help

 

- ACT/VAT = Air charge temperature / vane air temperature (means sensor that measures the temperature of your incoming air)

- EGO = Exhaust gas oxygen sensor (means sensor that measures the amount of oxygen in the exhaust. The amount of oxygen is a measure for how rich/lean your engine is running)

- HO2s = heated O2 (oxygen) sensor, same as above.

Both of these sensors are easy and comparatively cheap to change, but needn't be the cause. Bad contacts and un-insulated wires to/from these sensors will trip error codes, an oxygen sensor might burn out due to an exhaust leak.