The temperature gauge goes up too, which I've never seen on my truck. So I quickly connect my Xcal3 and start datalogging the cylinder head sensor and it's reading 235 F! I'm staring to crap my pants at this point when suddenly the temp sensor on the dash throttles to the hot end completely and the message center on the truck reads "reduced engine power". So I pull over and check under the hood. The engine is not overheating. I just installed e-fans about a month ago and I got to know what the rad hoses feel like as well as temperatures I measured throughout the motor with an infrared temp sensor. No boil over, top rad hose seems correct temperature. So a few minutes later I get in the truck and take off. Same thing happens a few minutes later and again nothing on the truck seems wrong.

So I'm thinking I might have a bad CHS, but I wanted to test it a bit first before buying another. They pretty cheap, but it doesn't look easy to get at. Does anyone know what the resistances of this sensor are at given temperatures and is the wiring more accessible somewhere else so I can measure the temperature of it while it is still in the head?

Thanks.

PS: When my truck went into this mode, the check engine light did not come on (and it works) and the A/C did work and I seemed to have normal power. I guess I wasn't in fail safe mode, but a warning mode.

 

what motor and mileage? when was your last tune up if ever? may be time for it. if you noticed no power difference then that could meen that your so use to how its been running and the gaps on your plugs could be getting too large and the light has decided to come on now because it lost the power and you didnt notice because it lost power very slowly. just a thought.

 

5.4L 3v with about 100k kms. Just changed the plugs a few months ago. I installed the efans about a month ago and was monitoring the temperature of the CHS and it ranged from 190 to 202 F. Never 230-240 F. I did find another post that said the fail safe mode is at 258 F so I never actually got that high. The message I got was probably more of a warning cause I know I was running on 8 cyclinders. Either way, I don't believe the numbers I'm getting from the temperature sensor and I want to test it for accuracy. I'm hoping someone has the temperature vs resistance chart and knows where the wiring might be exposed so I can measure the resistance.

 

what brand plugs? if bosch then take them right out and put a set of motorcrafts in it. any of the cheap brand plugs will cause issues like this and you could burn a valve. and if i'm not getting through to you then search "what bosch plugs can do!" which was posted by torkum and you'll want to get them out. as for the overheating according to the gauge, did you make sure the fans were running? and just so you know the closed coolant systems can run up to i believe 260 and not boil. and the gauge would read hot because its suppose to be around 190-200*f

 

I put in Autolites. My A/C was running at the time so the e-fans were cycling on a regular basis with the compressor. I've been monitoring this gauge for months now. Since I bought the Xcal3. I've never seen it go above 205F. Even when pulling my trailer.

 

autolite is a good plug and they make fords plugs but they dont meet the heat range that the engine requires unless you get the motorcrafts because they are the ford spec plugs. jbrew has had problems with his truck running on autolites and he put in motorcrafts and fixed the problem. you may have burnt up the autolites. and i guess someone else can help you with the temp gauge issue your having.

 

Matts Ford, your answers are subpar. That guy gave you a ton of data and your hypothesis was so not even close to his diagnosis.

 

You reopened a 9 year old thread simply to say that?

 

Well alhrocks what's your diagnosis, hurry up with it because it's been 9 years and this guy needs to get this fixed.

 

I just had this same issue yesterday. My truck has 176000 miles and just replaced the spark plugs with Motorcraft last week. I was pulling a trailer on the PA turnpike when the truck started beeping and the "Reduced Engine Power" notification came on. The temp gauge was pegged on "H". The truck never really seemed to be having a problem although I slowed to 40 MPH and got off at the next exit which was only 4 miles. I turned off the engine and let it sit for 30 minutes. My friend was behind me so he took my trailer. I started it up and the truck ran fine for the rest of the trip home (2 hours).

Any clue?

 

 

Did you ever figure out what it was? We are having the same issue. Thank you.