2001 ranger xlt, 2wd, std cab, manual trans, 2.5L I-4 (dual quad)
ERROR CODE: P0117 - engine coolant temp circuit low

I am encountering an issue with rpm runaway. Ill pull it out of gear and the RPM's run up to 2.5-3k. Thought it might be an issue with cruise control or sticky throttle. Unplugged cruise control module, tightened throttle linkage and cleaned the linkage arm. Better for a a day, then right back to the issue, progressively got worse. Pulled the codes from O'Reilys cheap equipment, code posted at top. Most of the info I was able to find on the web was not for the dual quad variation, pretty much all of it. Found and swapped both ECT sensors. Now the Check Engine idiot light is on. It is really rough to start now. The only way I can get it to turn over is to pump the gas pedal, it will backfire and start. I have to maintain about 1500 RPM's for 30 seconds then I can release the pedal and it idles like it should and wont die. Once running, it runs great with exception to the RPM runaway. Even with 3k RPM with my foot off the gas and the truck in gear, it doesn't have enough torque to maintain the gear with out me using the pedal. If it is running away I can usually tap the gas or come to a complete stop, and RPMs come down. I broke out my voltmeter here are my findings:

Orange clip: bigger hole 119.2 ohms and 9.51VDC. Smaller hole 4.2 ohms and .013VDC
Black clip: bigger hole 19.54ohms and 4.65VDC. smaller hole 4.3 ohms and .015VDC

Neither connector nor the the wires have visual damage, but joins a main bundle so I couldnt inspect the length.

P.S. looked at other threads, couldnt find any with this ECT issue

 

Have you tried to start with ether in the air box?
If it tries to start it might be a fuel issue


Any new codes?


The book I have, Powertrain Control/Emissions Diagnosis Service Manual, has the solutions of PCM reprogramming, or replace fautly ECT sensor, if there are no wiring issues present.


Most of the steps in this manual are better performed by the technician with the proper OBDII programming.


On this small engine I would suspect a blown head gasket.

 

no new codes. the troubleshooting recommendations are:
ECT/CHT damaged connector, sensor fail, signal circuit shorted to ground, or PCM fail. Im in school for aviation maintenance so if I can fix it I want to. Also replaced both ECT sensors. havent tried the ether, im pretty sure its not the fuel. The rough start started right after I swapped the coolant temp sender switch (Orange connector). RPM runaway more intermittent now than it was before ECT swap.

 

I agree, can you get the PCM reprogrammed?

 

Ill see what I can find for the PCM reprogram. Strange that resistance was so far off, and it started right after ECT swapped. Ill try the reprogram tonight and will post results and any codes that come up

 

Welcome to FTE.
You may have more than one problem.
On the runaway rpm, next time it happens disconnect the IAC electrical connector & tell us what happens.

 

RPM's only run up after I put it in neutral. generally when I come to a stop (or near stopped) it runs back down to about 800 RPM (Where I had it with no issues), Ill have to find a side road, let it run up, park and ill give it a shot but it will be back at 800 RPM

 

Have you upgraded the air box to a free flow type filter?


What's a dual quad?

 

I did upgrade to the K&N replacement for OEM a few years ago. No issues. Since these issues have started, it's been cleaned and replaced with no change to current issues. (Dual Quad is 4 cylinders, 8 plugs)

 

If this is a typical/plain jane 2 wire Ford ECT it should read around 2,000 ohms engine warm or around 30,000 ohms engine cold. If it's reading 2,000 ohms cold it will be too lean to start.