Running Rich? by Mattdel
 

Ok, so I've seen a bunch of people asking about running rich, what causes it, etc... Because of the age of our fox body's, the engine coolant temp(ECT) sensor is more than likely the cause, if everything else seems normal. But no one knows the proper way to test it. Well, here ya go. Pics provided.

Alot of people think that the computer uses the same sensor as the gauge. This is false. The sender for the temp gauge in your dash is located just to the right of the distributor.
The sensor that the computer uses is on the other side, near the #1 cylinder injector.

The Engine Coolant Temperature (ECT) sensor is threaded into a coolant passage with the sensing bulb extending into the coolant.
The ECT sensor is a negative temperature coefficient sensor, meaning that as the temperature of the sensor increases, the resistance will decrease. As the resistance value changes, the signal sensed by the Electronic Control Assembly (ECA) also changes. The ECA reads the varying sensor resistance and determines the engine operating temperature, using this information to optimize the air/fuel mixture and ignition timing.
The ECT sensor will also set a fault code when the ECA determines the output signal to be out of the normal operating range.
^^^ not always true, if the values are still within range but still subsequently wrong, no code will be set.

The ECT sensor has 2 wires in it's harness connector; a black with white stripe, thats the ground.
The other wire is Light Gray with a Yellow stripe, this is the one we will be testing.

Most Multimeters are capable of testing many different ranges of resistance, we only need one that can measure up to around 75 ohms. Select Ohms(anything above 75 is ok). Look for this symbol. Ω

The engine doesn't need to be running, only the key on, but you should test at different temps, and see the differences.

With engine at desired temp, place the negative lead of the meter into the ground wire of the connecter, being sure that it is touching the metal inside the connector.
Place the positive lead of the meter into the connector Gray wire, and use charts below

http://i133.photobucket.com/albums/q.../sensors-1.gif
http://i133.photobucket.com/albums/q...tang/chart.gif
http://i133.photobucket.com/albums/q...ang/chart2.gif

Thanks to Mattdel!

For Mattdel (Acer2428)
 

I do short distance driving patterns. The car barely warms up before I have to shut it off. I want to try a parallel resistor on the temp sender to lower the resistance (and voltage) under all conditions. This will make the engine think it is warmer than it really is during warm up and result in a leaner warm up mixture. Additionally, I want the computer to think the motor has reached 178 degree closed loop temperature a little earlier than 178 degrees.

My question is at what 'high temperature limit' does the computer think the motor is too hot and either turn on cooling fans or richen the mixture, or whatever else might happen. I want to tune the parallel resistor to read hotter BUT not create another problem.

Thanks for any insight.

RJ

You need a tune.

The computer uses the 02 sensors and if you do what you do, it will correct.


The ecm will always go for OEM target values, and when a dyno tune is obtained, substantial gains are had at the rear wheels and drive ability.

Dude, you replied to a thread from 5 months ago. ;)

Ya and the previous poster before that woke a thread that was almost 2 years old.:D

dude....check out the first post ;)

waking this post again
 

I have a blind mechanic and my dash temp gauge was not working.so he decides to hot the wrong plug and grounded out my ect before realizing it was'nt the temp sensor for the dash. well now the vehicle will not idle untill it gets to what 600 degrees if I read the book correctly, then after it gets to temp it will not take any throttle and is running very rich. will this effect the pcm ? how do I reprogram the pcm. the battery has been disconnected.I changed a few sensors. is there a choke assembly on an 88 5.0. this is my 1 st. fox body. been driving 1967-68 all my life. I don't want this purchase to be a mistake. any help would be greatly appreciated.

Whoa, talk about grave digging. I forgot I wrote this.

Anywho.. your PCM is probably cooked. Might be repairable by someone that does that kind of stuff, but might be easier to just replace it. You'll need to find out if your 88 is a MAF design or SD. I have an SD computer laying around you can buy off me.

whoever you had working on your car.... don't ever go back to them..

What do you need to get for the pcm? It is an Sd. Is there a test you could do on the pcm?

Bonesaw