My Truck is an F-150 supercab with the 4.6L. Here is the Info:

Temperature Readings (after Warmed up & with heat full on):

Dash Sensor- about 1/3 from C on the C-H scale
At Thermostat- ~140 Degrees
Heater hose(inlet)- ~138
Heater hose(outlet)- ~130

RPM at idle in park- 1000
RPM at idle in drive- 900

Observations:

Engine idle speed fluctuates slightly- believed to be a/c compressor cycling (a/c is not turned on).

Fluid is at correct level

There is no problem getting heat in the cab

Work preformed (futile attempts at a solution):

Seafoam treatment through brake booster line
Remove TB and clean all- one EGR port was plugged
Remove, clean and lubricate IAC
Replace thermostat (195 Degree stant)
Clean MAF sensor
Replace Plugs, wires, PCV, fuel filter, air filter.

Conclusion:

After all that work engine still high idleing and running cold. I am in a colder climate average temp in 20's this time of year. i wonder if high idle is caused by cooler water temp? like the engine is trying to warm up... but cant get there?

i just replaced the thermostat.. but the temp readings lead me to believe the new one is opening too soon as well. hate to change it again if not needed..

any suggestions?

 

Hi and welcome to the forum

An engine running too cool will burn more gas than normal.
Do you know anyone with a scan tool that can read live data? Checking the engine temperature by looking at the ECT (Engine Coolant Temperature) reading is a more accurate way. Even in 20 degree weather it should still get hotter than what it appears to be now.
The engine temperature shouldn't have much effect on the idle speed. I'd be looking more for a sticky IAC or maybe a vacuum leak although that will usually cause a rough idle too.

 

Temperature Readings (after Warmed up & with heat full on):

Dash Sensor- about 1/3 from C on the C-H scale
At Thermostat- ~140 Degrees
Heater hose(inlet)- ~138
Heater hose(outlet)- ~130


I was wrong in my previous post. If it caused you any grief, I'm sorry. I read HEATER hose (inlet) and I typed HEATER hose inlet. But I was thinking RADIATOR inlet hose. However you checked the temps above, do the same at the radiator inlet hose. If it is near the ~140 degrees measured at the T-stat, than you should check the T-stat as I described.

Racerguy is very knowledgeable. Do what he say.

 

Thanks for the replys. i understand what you guys are saying... i need to get the ECT, the sensor appears to be a thermistor- i dont know anyone with a unit to hook up. does anyone know where i can get resistance tables for it?

 

Just another tip....if the IAC is bad, then cleaning MIGHT help, and if so...only for a short time. If you noticed any improvement after cleaning the IAC...replace it. If you already have, then just ignore me and I'll flap my lips elsewhere.

 

I'm having a hard time making a table here so this is a bit hard to read. Hopefully I can fix it later.



°C °F Voltage (volts) Resistance (K ohms)
120 248 0.27 1.18
110 230 0.35 1.55
100 212 0.46 2.07
90 194 0.60 2.80
80 176 0.78 3.84
70 158 1.02 5.37
60 140 1.33 7.70
50 122 1.70 10.97
40 104 2.13 16.15
30 86 2.60 24.27
20 68 3.07 37.30
10 50 3.51 58.75

The voltage readings shown are based on 5V reference voltage going into the sensor.

 

When I read that my Ford temp "guage" was no more than an "idiot light" I became very nervous. Aluminum heads + overheating = warpage. I wanted a real temp guage. I also wanted an RPM guage.which my '98 didn't have, and a MPG readout to adjust my driving style for max MPG. To buy and install these three cost more than I wanted to spend.

Then I read abot this: http://scanguage.com/

I bought for ~$100.00 and am very happy with it. It plugs into the diagnostic port and displays ECT in degrees F or C from the sensor, RPM, MPG plus alot more. Check it out. I'm not connected with the company in any way. Just thought you might be interested.

 

FWIW, the in dash temp guage is a 'real' guage. It has its own sending unit that is in the coolant flow. The computer uses either the ECT or the CHT, depending on which engine is in use - you didn't specify which you have. It is that sensor that your Scanguage device is accessing. FWIW, I can hook my laptop up to my truck and do the same thing for diagnostic purposes. Any good scantool will also have this capability.

It's the oil pressure one that's just a mechanical idiot light.



Steve

 

I have the 4.6 Vin 6 Engine.

How exactly did you hook your laptop up to get this diagnostic info?

 

I have a Laptop. The only way I know to "hook it up" to the diagnostic port is to buy the software needed to read the digital info it puts out. The software is packaged with the cable which attaches to the diagnostic port at one end and the USB port of your computer at the other. The package is $expensive$ last time I checked.

This "diagnostic software is, IMHO, far superior to the Scanguage. But is NOT what I wanted. I wanted RPM, Coolant Temp and MPG guages. The fact that it displays OBDII codes plus many other things was a bonus.

As far as the "factory" temp guage is concerned, I've read comments from many posters who called it no more than an "idiot light". Coolant temps as high as 235 degrees and it doesn't budge,it is so dampened. I like to see a number. What is the ECT. Is it 220 degrees and climbing? Or is it 198 and steady?

 

Yeah i know what you mean... I am seriously considering the scangauge, for the money it seems to have many features. Information like ECT, MPG and the ability to read codes make this unit attractive. Too bad it's so ugly... they could put it in a nice black case, and put a decent screen on it for a marginal price. Or better yet, make it operate as a remote screened unit, with the screen and input devices separate from the rest. The next thing to consider is the mounting of it... i'm thinking right behind the shifter, low enough to still read it when the shifter is in the drive position. anyone else have one? what do you think?

 

I decided to Contunue this scangauge issue in a different thread. Please post any more suggestions regarding the original post.

Regards,

Matt