I'm going to go buy an OBD1 testing unit to figure this out myself, but I thought I would run this by you guys to see what you think. My family has owned this truck since the end of 94' (95' 5.0L XLT 2WD) and it has -never- thrown a check engine light. I've driven it for three years myself and never seen one. I was coming back from someone house this weekend in heavy traffic in Houston, trying to get around some idiots so I could make my exit. I hit 80mph, and my check engine light came on. It stayed on for maybe 6-7 seconds then went off. I continued my drive home (about 30min) and it never came on again. Faulty electrical or actual problem?

 

You dont buy the OBD1 tester, just look at this thread to do it-
https://www.f150forum.com/f10/how-re...es-obdi-10907/

It makes the CEL flash and you just count the flash and look up the corresponding numbers.


Did you "race" up to 80mph or was it kind of easy acceleration?

 

If your engine isn't MAF, your K&N intake will push you into leaning out under load. How old is your 02 sensor? Their switching speed slows & accuracy diminishes w/ use (I change mine @ 30K. 60K should be max, especially if your tend to run lean anyway). A Fuel delivery reduction can also do it.

 

Last time I averaged 80mph, my whole rear view mirror lit up. $518. but radar did verify I was averaging 80MPH. You can do the codes manually but .......http://www.handsontools.com/Equus-In...ol_p_5574.html

 

The light came on... okaaay. You won't know squat until you read the codes.

 

Call it a hunch!

 

The old girl's tongue was probably hanging out, tellin ya to slow down.

 

Yes, my truck is MAF and no it is not running lean, it is actually running quite rich with advanced timing. The engine's internal's have been built, bored .30 over, new pistons, new cam, etc - so the "old girl" wasn't begging to slow down :P She's seen 120mph. Also, yes I can buy an OBD1 sensor, I already ordered it. The "Equus Innova 3145 OBD-1 Ford Scan Tool". The O2 sensors probably do need to be replaced, thanks for the tip on that. Im not sure if they have EVER been replaced, and my truck has close to 240,000 miles.

 

Also check temp sensor not sender and wiring, my old truck had a corroded wire and it ran rich.

 

Very helpful to wait till the #8 post to mention that. Check fuel pressure including blead down. If the computer starts shutting down the injectors around
80-85mph.........nevermind.