I have a 1992 F350 with a 5.8L or 351CI EFI however you prefer that is severely lacking power. It has a standard transmission and so have been able to determine its not dependent on RPM. Its hard to start when its warm, requiring a quick burp of the throttle while cranking and then it will fire up and idle fine. Starts fine cold. One odd thing I have also noticed is that it has way more power at night then day, i'm assuming because the air is denser. In the day it can hardly pull itself 80kph and at night we were pulling a stock trailer uphill at 90kph and accelerating. Too me these symptoms seem to point to a rich running condition but I can't find a MAF sensor, IAT sensor, or anything really that i'm familiar with on my daily driver pickup. So my question is does anyone know what is responsible for fuel control on these trucks? Is it all done by the O2 sensors or are the other sensors just hidden where i can't see them? Or has anyone perhaps had this problem before and thinks i'm going in the entirely wrong direction? thanks!

 

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First run a self test see if it reports anything.







Let us know what you find if anything, you should either get system pass or error codes one or the other.

Your codes will be three digit.

 

The EFI computer is responsible for fuel control so you need to ask it if there are any problems by following the procedure outlined by Danr1 above.