Hey Ron: I've got a 91, 2.3 that has random power loss after it warms up a little. I can't get the RPMs over about 2000. It doesn't always happen, but it's happening more and more. I have replaced a good number of parts, including fuel pump, ignition control module, EGR valve, ETC sensor, plugs, etc. I just took it to O'Reilly's for another computer test, and this time it flagged 21 and 51, both of which may relate to the ECT. Could problems with this sensor cause my truck to lose power? If I have already replaced it, is there a way to test the one I bought to see if it's good? Any other suggested fixes? Any help welcome. Regards, Uncle Buck

 

Computer sends ECT sensor 5volts on one wire, if ECT sensor is cold(65degF) it will send back 3volts on the other wire(return wire), the colder it is the higher the voltage it will send back.
As ECT sensor warms up voltage will drop on the return wire, at operating temp, 195degF, the voltage on the return wire should be under 1 volt.

The 5volts the computer sends out is shared by a few things, ECT sensor, Air Temp sensor, and Throttle position sensor.
test for the 5volts first

 

Ron: If the sensor is defective and never sends out the correct voltage when the car is warm, will this cause significant power loss? Could this account for my problem? Thanks. John

 

Ron: Just tested sensor. I get five volts going in. JXM

 

What was the "out" voltage?

It should get lower as engine warms up.

Don't think it would cause loss of power to the extent you describe.
And MPG would be down from running too Rich.
Check a spark plug and see if engine is running too rich

 

Ron: The out voltage, while truck was cold, both before I started it and after, was 1.8 volts. As the vehicle warmed up over about 10 minutes of idling, it moved up to about 2.4 volts and stayed there. Curiously, the in voltage, which had been at 5 when car was cold and turned off, dropped to about 4 volts when it was running. I suspect this only clouds the issue, but any analysis welcome. The sensor is new, but for $20 bucks, I can buy another if that's a prudent move. And by the way, Happy New Year. I got to bed at 9 p.m. and for me that's a happy ending to 2015. Regards, JXM

 

Yes, Happy 2016

We went to bed at 10:00, had our 3 year old grandson staying over.
Wife and are having a bet on when we hear from his parents today.........my bet is tonight, not today, lol

Have a look at this diagram: http://www.therangerstation.com/tech...ls2_3_3of3.JPG

It shows a different wiring than I thought, Gray/red stripe wire comes from pin 46 on Computer(EEC), that pin is listed as EEC Ground, I assumed it was hooked to pin 26, which is the 5volt power from computer.
This Gray/red wire runs to pretty much every sensor including O2 sensor via Orange wire.

I have this diagram for the EEC: Ford EEC-IV

I wouldn't get a new ECT sensor, I would test that Gray/red wire at other sensors to see if it is a ground, seems like an odd setup and either diagram could be wrong,
but this 2.9l diagram shows same setup: http://www.therangerstation.com/tech...ls2_9_2of3.JPG

Pin 46 as the common reference for all the sensors

 

Ron: Thanks for the interest and advice. I'll get to this chore over the weekend. Will also check plug to see if running too rich. Plugs are new so it should be easy to see. Regards< JXM