Ok, just got a code reader. Did the koeo test, showed 51. When I the truck about 3 weeks ago, it over heated do to hole in water pump but the factory gauge never registered an overheating it just bounce from low to mid way. I replaced t-stat and pump and put in a trusty mechanical gauge were the ect was. Temp is good. Before all this the check engine was on and rough idle from 700 rpms and lower and shuts off when temp on engine is low. I want to keep my mechanical gauge but how can I trick the computer or do I really want to do that? 1988 f150 5.0 ego with 120k on the odo.

 

Did you take out the ECT for the gauge or the computer? The one for the computer is in the pipe of the thermostat housing and it needs to be there.

 

"1988 f150 5.0 ego with 120k on the odo". I got the "odo", but "ego"?

No getting around accurate ECT "sensor" input. 51, you'll get if you didn't prewarm the engine to norm op. temp before testing. Coolant temp "sender" goes to the gauge.

 

I removed the sensor at the front of the engine on the drivers side just right of distributor. Picture in my book shows it in the t-stat housing, but Tue housing is not threaded for one. Not sure of any other sensor, were is the other one located?

 

I was thinking 4.9 again. On the 5.0 they're pretty much right next to each other near the distributor. The one for the gauge has one wire and the one for the computer has more than one wire.

 

EFI, sorry. 200 Degrees fully warmed up.

 

Water temperature switch = Coolant Termperature "Sender"

 

Yes just one wire.

 

The one wire sender doesn't need to be there. I'd try a new sensor for the other.

 

Above the T-stat housing. ECT mounts horizontally. Slightly obscured. If you reach back in, you'll run into the wires.