where is my engine coolant temp sensor

[DCannon2763]

I have a 98 f150 5.4 L 4x4 I cant find the coolant sensor the coolant switch is just behind the alternator by the thermostat housing but the sensor isnt there where is it?? pictures or discriptions will help thanks

[torkum]

Do a SEARCH on 'Cylinder Head Temperature Sensor'.

[DCannon2763]

I didnt think they switched to those and did away with the engine coolant temp sensor until either 99 or 2000

[DCannon2763]

can anyone help??

[Paralyzer]

its under the intake maniflold. screwed into the passenger side cyl head.

[DCannon2763]

can i get to it from the top do i have to remove anything to get to it??

[torkum]

Yes you can and thats why I told you to do a search on CHT. To remove take the alternator off and you can reach it but its harder putting the new one back in. Once you get the thread started it will get easier.

[jbrew]

I guess he doesn't want to search torkum, not sure if it's working yet.

BTW - That's a temp sender behind the alternator. The bulb on the bottom corrodes over time and needs to be cleaned/taped/reinstalled.

The PCM uses info from both sensors to cipher on the 98. IE: ECT/CHT.

What's the problem with it anyway?

The 98 5.4L CHT =

[DCannon2763]

sorry my skills are kinda basic but the truck runs fine half the time and half the time at low idle exspicailly as soon as it is started the truck will idle real low and real rough and sometimes it will die and at this time it dont matter how much you press the gas pedal nothing changes a machanic told me that the temp sensor is out and telling the computer the truck is hot when it is really cold and vise versa

[torkum]

That sounds more like a IAC [idle air controller] problem. Do a search to see if others description meets your symptoms.

[Neal]

HI!... Here's a pic :



You can see it on the driver's side of the engine just under the 1st intake port on the cylinder head.

It can be changed out with the intake manifold still in place but it's a PITA! Just pull the intake manifold off. The intake gaskets are reusable so there are no parts to be bought to re-install it. Good time to to a plug change while it's off. 100 times easier. Another one of FORD engineers great ideas where to place a sensor.

[jbrew]

Originally Posted by DCannon2763

sorry my skills are kinda basic but the truck runs fine half the time and half the time at low idle exspicailly as soon as it is started the truck will idle real low and real rough and sometimes it will die and at this time it dont matter how much you press the gas pedal nothing changes a machanic told me that the temp sensor is out and telling the computer the truck is hot when it is really cold and vise versa

How did the mechanic determine? Did he/she run diagnostics? The mechanic is desribing what the PCM intiates -"limp mode". You should have a check engine light on regardless.

Make sure your check engine light works. - Turn your key to the run position without starting. Does the check engine light come on?

If so - I think it's just what torkum suggests. Also clean your MAF sensor.

Yea , don't go for the ECT CHT yet unless diagnostics were run to determine. Other than that , sounds like a bad guess to me.

[DCannon2763]

I have a brand new IAC and MAF all new plugs all new coil packs all new O2 sensors my engine light is coming on it is giving code p0171 which is a lean code he ran some test he hooked up something to the port in the cab and watched it while it ran but i dont know what

[DCannon2763]

could it be a vacuum leak? how could i check?

[jbrew]

Why the hell didn't you say that at first ? Yea , use the search bar.