high idle problem on a 4.0

[creepinjeepster]

If you believe it to be a shorted wire and can't find the short, try disconnecting that wire and running a new wire in its place (like through the door and into hood). If it fixes your idle by doing this than it will confirm your theory of it being the wire and you can run a new wire in its place.

 

[mailboxman]

Thanks Creepin--thats what I'm thinking--do you know if the PCM is the same as the EEC??? I am not sure if unplugging the EEC is the correct way to check this wire from the ECT---does the ECT send its signal to the EEC?? I know the wire on the ECT in question is grey with a thin red stripe--I cant find this wire on the EEC--

If this is something really stupid like a bad ECT sensor I am going to flip--i bought this sensor from Advance and wonder if I should go purchase another brand and try it---this eec-iac-ect shit is gettin way over my head

 

[Ranger44]

No, No, No, No

That's the Electric shift control module for the 4x4.

Ford call the computer a PCM. Powertrain Control Module.

If this is on a Ranger, it's located in the drivers side very back side corner.

 

[modelageek]

I am confused. On my truck where is the pcm/ecu. on trucks with 4x4 where is the electric controller for them.

 

[mailboxman]

wow--i learn something new everyday??? I do see the pcm tucked behind my cruise control----i will definitely have to pull the cruise control to get to this thing---

So--do I unplug the PCM and check for continuity in my coolant temperature sensor wires??? Maybe I will find some corrosion on the plug since this is exposed???

I found a schematic for the pins on the pcm and will try disconnecting the plug and see if i still have resistance in that wire

You guys have been great with all the help--thanks--i am gonna do my best to not have this thing beat me---i am still wondering if i should go to another auto parts store and buy another coolant sensor???

That sure sounds easier than getting into all this wiring that I know nothing about---what i do recall though is pressure washing that corner of the engine bay where the pcm is and hitting it pretty good---wonder if i am going to find corrosion or are these things pretty well sealed????

 

[Ranger44]

DO NOT let EFI scare you. Just understand it ALL is based on the principle of Input, processing, storage, and Output. Basic example: The Oxygen sensor measures the exhaust (Input), PCM processes this, and then changes the injector pulse (how much it puts out) (output). If you break it down like that, it's cake.

After taking 3 Rangers down to the frame (stripping them for parts), adding/designing my own circuits for aftermarket lights, fog lights, OBA, Cruise, etc., and having a Ford EVTM..........It'll all seem childishly simple. Especially since we are dealing w/ EEC-IV.

Just to eliminate the wiring, check it. Just undo the 10mm bolt. As you are, be careful aboutr how it comes out, it'll want to cock to one side and bind. Unplug. Unplug your sensor. Find the corresponding wire at the PCM plug. One lead in the PCM pin, one on the sensor pin (wire of same color). Check for continuity. It's that setting that'll beep when you touch the leads together. If that's good, move on to a resistance check. Do the same thing. Record the resistance reading.

I'd do this for both the ECT and IAT.

IAT: Your location is in the bottom left corner.

Btw, just buying a sensor isn't a way to fix anything.....

 

[Ranger44]

Did you ever get a resistance reading across the ECT?

It should be pretty high with the engine cold. Like 40-60 ohms. Between 50-70 degrees F.

 

[lifted92ranger]

what is the TPS? IAC??

 

[lifted92ranger]

never mind

 

[mailboxman]

Ranger 44--I wish i had your smarts--unfortunately I dont--i pulled the plug from the pcm tonight--i checked for continuity again on the ect wire and it was showing shorted just like it showed before unplugging--I started checking wires and it looks like there is a factory splice on the ect wire (it looks to be green or gray with a thin red stripe) with a black wire spliced in that goes to the firewall and is grounded with a copper bolt---this is freakin nuts???? I even took the copper bolt out and removed the black wire and reconnected and my cel went on and the idle was around 2000rpm.

I reconnected everything back up and will go to napa tomorrow and get a replacement for the ect i bought at advance---the wiring and everything else on this truck is in too good of shape to be shorted--i am banking on it being a bad ect, although i cant explain why it acted the same with the original ect????

I bought this truck because it is so cool looking and i was looking to have some fun with it--but something that possesses you like this idle sure takes the fun out of it.

unfortunately i have been using a sweep multimeter because i dropped my digital one and broke it---the pins on the ect are almost impossible to reach but i did make momentary contact and resistance was very low and engine was cold.. if the ect turns out to be bad--i will never shop advance again--i have a carquest and a napa that are a little out of the way but it will be worth it.

 

[mailboxman]

Here we go again--replaced my digital multimeter tonight and rechecked ECT engine coolant temp sensor, the ATS air temperature sensor, and the TPS throttle position sensor. All three are working and are within spec!! THANKS 44 for the Btw, just buying a sensor isn't a way to fix anything.....

So I bought the $10.00 meter and saved the $33.00 NAPA wanted for the new sensor. But Its still idling high--

I unplugged the new IAC motor and the idle went down???? to right around 600--I will look up the IAC test tonight and perform it tomorrow

I keep thinkin vacuum leak but I cant find one---

 

[mailboxman]

OK guys--this one beat me--i checked and rechecked all sensors and reran codes--nothing is showing bad--once again, when I disconnect the iac the idle goes to normal but this presents other drivability issues--I am going to try and find a shop locally that can diagnose this--appreciate everyones help--I will post back with outcome.

 

[mailboxman]

Update--I went to a local mechanic at lunch today and explained everything I did--he looked at the tps sensor and said to replace it with a motocraft!!!

I just ordered one online at silverstate ford--they had the best price--$52.00 w/shipping

I will post outcome--again, thanks to all

 

[94b4kzoomzoom]

this may sound dumb, I did find that when I changed my coolant in my truck if I didnt have the proper amount of coolant in the radiator my truck stayed above 1200 rpms and got up to temp quick, I poored the correct amount and it ran fine after it got up to temp.

 

[modelageek]

i dont think the coolant thought is dumb . On my truck if the coolant is not completely full and all air out of the systems the 2 sensors that sit in the outlet housing do not work properly because they are not completely submerged in coolant. and with certain parts i only buy motorcraft. ie. sensors, thermostats, etc