Couple days ago I posted that my engine temprature guage quit working. Along with that the check engine light is on. Now this morning in starting the truck it revs up to 2,500 rpm and slowly goes to idle. I am hoping these are quick fixes and not the beginning of a headache. What can cause these problems? Forgot to menion its a 2005 XLT Screw with the 5.4.

 

Sound like a coolant temp sensor to me. That would explain the check engine light as well. When they fail they default to -40 which would cause the truck to run very rich as well and that would be the cause of the high idle at first. It is somewhat normal for it to idle high at start up and go down if the motor is cold. That's what I would say.

 

what code is it ???

 

I have not pulled a code yet, don't have a scan tool. I am work right now so I can't get to a autozone. Is the temp sensor mounted at the radiator or near the thermostat? Thanks for the replys

 

its screwed into the block

 

https://www.f150forum.com/f4/2006-f1...cation-113292/

 

Thanks PicaFlor...great break down...

 

Yes thank you! Way better then describing it.

 

Finally was able to get around and pull a code. P1289 MAFS. Is there a possiblity that the temp guage not working is throwing off the mafs and into thinking the truck is cold? causing the high idle at first and check engine light.