and I think I know why......

Just a bit of background, for several days now my truck would run normal as the engine was warming up to operating temps. After the truck was fully warmed, I started losing power. Take-off from a stoplight was slow, sluggish, and there was no throttle snap. Top end power and boost was dropping. If I romped on the pedal, it felt like it was defueling. Also the truck didn't want to downshift such as when passing, etc. None of those symptoms are present if the engine is still cold.

So I plugged in AE and ran some tests. Everything is normal. Started monitoring live data and found that my coolant temps were off - way off. Gauge showed normal (as normal as it always does for the Ford factory dummy gauge, meaning dead center and never moving), but under AE my coolant temps were reported at 280 degrees Started wondering if the gauge was wrong, or if it's just the PCM is seeing the wrong temps, so I checked the oil temps. That was only 207 degrees (oil temps are normally only slightly above coolant temps), so I figured by that report that the PCM is seeing the wrong coolant temps and is putting itself into a kind of limp mode. That would explain why the truck runs normal as the engine is still cool, and falls on it's face once it reaches operating temps.

If I remember to do this, then tomorrow morning I'm going to hook AE up again and look at coolant temps before cranking the truck. I just want to get a baseline to see if it's reading some funky number before the engine has warmed up.

As for a fix, I guess I'll need to swap out the coolant temp sensor. I have never paid attention to where it might be located. I'm guessing somewhere near the thermostat?? Anyone know for sure?

 

<style></style>Page Unavailable

There is also a temperature sender gauge switch if you need a picture of it.
Click on link even though it says unavailable.

 

Linky no worky for me. Is there a part number I can throw in the search box on the O-Reily site that will lead me to that page?

 

Curtis,

I assume you have an automatic....

The wiring diagrams for an '02 show that the coolant temperature sensor is ONLY used on manual transmission-equipped trucks. The TFT (transmission fluid temperature) sensor is hooked to the circuit that WOULD BE the ECT (engine coolant temp) sensor on a MT truck. The TFT, IAT 1 and 2, and EOT are the ONLY temperature inputs on your AT-equipped truck.

 

Cody are you sure??? Because I just went outside and popped the hood, and right next to the thermostat housing is a temp sensor mounted in there. Looks like that is the coolant temp sensor.

However, what I'm wondering is if that is for the gauge only, or if there is something else I'm missing. The reason is the gauge temp never moved past halfway, yet the PCM was seeing coolant temps well beyond what would have fried my engine. I'm just thinking about that discrepancy and trying to figure out what I'm forgetting here.

 

Oh, and I have tracked coolant temps in the past when playing around with AE. Particularly coolant temps vs oil temps. Oil temps were always about 10 degrees warmer when the engine has been running at operating temps. So this sudden jump in coolant temps is something new.

 

i wonder if ford might have installed the engine coolant sensors after the 2001 F-series models because i checked my truck and it has the engine coolant sensor right underneath the tranny temp gauge

 

Well I also got this from the service manual:

 

Sounds like you're looking at the right sensor. Look in the manual under Group 3 Engine. Scroll down to the bottom of that listing. The last one is 303-`4B Electronic Engine Controls - Diesel Engine. Under the removal section you will find the ECT instructions with a diagram.

Edit: Good catch on the coolant temperature reading being your problem. That's probably the last place I would have thought to check.

 

Just some thoughts.

Can you just unplug it and see if truck runs better? Or will it error.

Or maybe pull sensor, toss in a plug and take for a test ride while it is dangling to make sure before you spend the money.

Man, I got to get an AE.. It is on my santa list.
Yes indeed. Good catch.

 

Just subscibing to learn somethng new......

 

Check these two wiring diagrams. You will see the manual/automatic differences. Pin 37 is the input to the PCM on the orange w/black tracer wire.

On the second picture, the continuation at "K" shows the splice to ground. This is from ALLDATA.....and these are ACTUAL Ford diagrams.

Don't take it as gospel....it's just a representation.

 

I forgot to add that USUALLY...and that is used loosely......a temperature sensor used for PCM input will use TWO wires. A sensor output wire and a ground wire. A sensor used for a gauge will usually only have one wire since a discrete, high quality ground isn't really necessary. The discrete ground wire will supply a more consistent, low-noise ground to the sensor's output resistance as well as be on the same "ground plane" as the PCM that cancels out any high-resistance ground issues (corrosion on threads or teflon tape, etc.).

 

Pocket, whats an ae? Never heard of one, but with how you found such an odd problem with it, it sounds like it might be handy to have.

 

AutoEnginuity.