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Hello all and thanks for letting me pick the collectiave brain. I'll say that most of m vehicles are from the 70's 80's and now this 94 F150. I don't have much history of vehicles with air temp and MAP sensors in the intake tract. I understand the theory behind them but that's about it. This truck runs fine above 40 degrees. under that it takes forever to start then only idles for a few seconds and dies. My first thought was fuel pump, but a fuel pump would not be weather sensitive. I looked thru the venturi of the MAP sensor and things look clean. The Air temp sensor looks ok except the Oring around it is cracked. Are there testing procedures for these?
Key On Engine Off (KOEO) self test. You can test fuel pressure - there is a test port with schrader valve on the fuel rail.
You can also jump the STI and signal return then count the check engine light flashes. I use an Innova 3145 code reader which displays the code so I don’t have to hope I counted correctly.
.....This truck runs fine above 40 degrees. under that it takes forever to start then only idles for a few seconds and dies. My first thought was fuel pump, but a fuel pump would not be weather sensitive. I looked thru the venturi of the MAP sensor and things look clean. The Air temp sensor looks ok except the Oring around it is cracked. Are there testing procedures for these?
Yes, with a DVOM you can test sensors rather than wholesale replacing.
Procedures are posted many times, search or someone with them bookmarked may post for you.
