How to raise idle RPMS

[Tsensational]

Engine Coolant Temperature Sensor (ECT) Mod - YotaTech Forums

Have any of you ever noticed your car running alot better before its fully warmed up in comparison to fully warmed up? Any of you want to raise your idle for whatever reason? Well this trick supposedly keeps your operating temperatures normal while letting your ECU think otherwise.

Taken from Toyota forums:

Engine Coolant Temperature Sensor (ECT) Mod
1/27/2003

Galen (Dr. Zhivago on the forums) shows you how he installed a device to modify the output of the Engine Coolant Temperature sensor.

Hey All,

First let me start out by explaining what the ECT is: The ECT (Engine Coolant Temperature) Sensor on our engines is a Negative Temperature Coefficient (NTC) Thermistor. What this means is that as the temperature of the ECT Sensor rises, the resistance of it drops.

Here's a chart detailing the characteristics of the ECT Sensor in our engines. This is from a Toyota training document. The ECT Sensor used is the same in all Toyotas.



As you can see by the chart, the Vertical scale on the right shows Resistance and the Horizontal scale shows Temperature. You can see the relationship between the two variables.

Why is this important to know? The ECT tells the ECU what the internal temperature of the engine is which determines a few things. One thing that it affects is how much fuel is dumped into the cylinders. When an engine is cold, the ECU delivers more fuel and runs more timing advance because cold fuel does not atomize as well as warm fuel.

By modifying the ECT Signal, we can fool the ECU into delivering more fuel into the engine and running a little more timing advance, thereby enhancing power and throttle response. The ECT isn't the ultimate authority when it comes to telling the ECU what to do, but it has a heavily weighted opinion.

The mod involves installing a Potentiometer (Variable Resistor) in series between the ECT and the ECU. By adding resistance to the ECTs circuit, the ECU believes the engine is colder and makes the above mentioned changes almost instantaneously. It's a pretty neat trick.

Since we are using a Potentiometer, we can "Dial In" the appropriate amount of added resistance and we can also turn it off with the quick turn of a knob. Once the Pot is wired into the circuit, the mod is initially adjusted like so: Start the engine with the Pot "Zeroed Out" or turned fully counter-clockwise. Then once the engine has reached normal operating temperature, slowly turn the pot until the idle RPM's have increased 250-350 RPM's. Take it for a spin to feel the results!

On my truck, I currently have the ECT modded idle set to 1050 RPM's. My normal idle is 700. On my truck, this seems to give the biggest kick and it does not "bog" between shifts. Too much ECT modification can cause bogging between shifts.

By the way, this mod has been around for over 10 years. I didn't originate it. I ran it on my 87 Supra Turbo with great results. I hadn't heard of or seen anyone running it on their 4Runner, so I thought I'd dust it off and install it on my truck. As usual, it worked like a charm. I've been running it for about 6 weeks now. In that time, it has not caused any check engine lights to come on, nor has it appeared to negatively affect fuel economy.


Midiwall was kind enough to put together a page detailing the installation of the ECT Mod on his 96 4Runner Limited. Mark was/is my Beta Tester for this mod. This article is not meant to be an "End-All, Be-All" how to for this mod, but merely a guide to get you started. We will refine it in the near future.

Here's a link to the article. I know you will all have questions. So, please feel free to ask away.

I hope you all found this is useful and interesting.

Dr. Z

PS Thanks Mark!

This link is the How To for the 4Runner. It includes pictures.

ECT Mod


For our ECUs, both GT and GS, Engine Coolant Temp Sensor is Pin #93

[bullet06]

You have anymore on this. I'm running rich right now but timing advanced and high rpm sounds nice.

[FeaRlezZ]

do we need a potentiometer or could this just b done thru the fic. . but yes this needs more clarification

[Tsensational]

Tuning does wonders in my experience, so this in conjunction with tuning would be nice. I tried looking for the chart for our coolant temp sensor voltages x temp graphs but didn't find any.

I do have a spare coolant temp sensor sitting around and can verify that it uses two wires like the Toyota guy.

[Tsensational]

Condensed to 1st post

[Tsensational]

Condensed to first post

[bullet06]

Shouldn't be a problem with the fic just need to know how are sencor reads. I like the idea. It would help with racing from a dig.

[Tsensational]

http://www.autoshop101.com/forms/h32.pdf

This PDF tells you how temperature sensors work. Ours is the ECT. I have one sitting on my desk as we speak so I can verify that we use this kind of coolant temp sensor.

[bullet06]

Get a water temp gauge and ill be doing this.

[Tsensational]

If you need any help with the ECU wiring part, feel free to ask.

[bullet06]

Alright thanks. I don't have my egr anymore you think I will need to do anything with that? Maybe make the car think I have it with the fic?

[Tsensational]

Not sure about the EGR and not sure how the F/IC could do anything about it, or how its related to this matter. You'll be tampering with the Coolant Temp sensor, not the Exhaust Gas temp sensor.

[bullet06]

The link sead the egr and iat worked with the ect. So I just wounded if not having my egr it wouldn't work? I still have the sensor though so maybe feed it some low volts to make the car read it?

[Tsensational]

Well if your car runs off a cold start without the EGR, it should be the same. Doing this will make it seem like the car is continuing to be cold and will advance timing a bit. If theres no problems now, it shouldn't make new ones.

[bullet06]

Alright. I do have cold start problems so that maybe why. Thanks!