Sensor Question

[81Cutty]

There is a sensor of some sort in front of the carb on my 3.8L V6 that is computer controlled. I need to replace the plug because when you move it the car goes from idling good to idling rough. I looked it up in my repair manual and it doesn't show a sensor where it is on my car.

All I know is that when you wiggle the plug/wire it quickly changes the engine from running good to running rough.

Any ideas?

 

[joe_padavano]

There is a sensor of some sort in front of the carb on my 3.8L V6 that is computer controlled. I need to replace the plug because when you move it the car goes from idling good to idling rough. I looked it up in my repair manual and it doesn't show a sensor where it is on my car.

All I know is that when you wiggle the plug/wire it quickly changes the engine from running good to running rough.

Any ideas?

Is it the two wire mixture control solenoid plug or the three wire throttle position sensor plug?

 

[81Cutty]

Is it the two wire mixture control solenoid plug or the three wire throttle position sensor plug?

It's 2 wires and on the intake manifold.

 

[85 Cutlass Brougham]

Post a pic of the general area it is in, and put an arrow or circle around the part in question. It's easy to do that edit in MS paint and it will help us to see what you are talking about.

 

[81Cutty]

Since it pretty much right on the front of the intake manifold, could it be a coolant temperature sensor? It would make sense because it never really wants to engage the choke and when you wiggle it the idle changes from good to rough instantly.

This is a picture off Autozone.com of a new one:
http://econtent.autozone.com:24999/znet ... 2/image/6/

 

[mhamilton]

If it's threaded into the intake itself (in the water crossover passage?) then it's the coolant temp sensor. Very important to the mixture control.

The choke is still a purely mechanical device, that works like any non-computer Rochester choke.

 

[81Cutty]

If it's threaded into the intake itself (in the water crossover passage?) then it's the coolant temp sensor. Very important to the mixture control.

The choke is still a purely mechanical device, that works like any non-computer Rochester choke.

Yeah, it's threaded into the water crossover passage. I figured it was something to do with the coolant temperature.

And, it has an electric choke and it is computer controlled.

 

[joe_padavano]

If it's threaded into the intake itself (in the water crossover passage?) then it's the coolant temp sensor. Very important to the mixture control.

The choke is still a purely mechanical device, that works like any non-computer Rochester choke.

Yeah, it's threaded into the water crossover passage. I figured it was something to do with the coolant temperature.

And, it has an electric choke and it is computer controlled.

Yes, the choke is electric on the Dualjet and no, the choke is not computer controlled. All it does is use an oil pressure sensor so that the electric heating element in the choke is only active when the engine is running.

 

[85 Cutlass Brougham]

The CTS is important because it tells the computer to run in closed loop and start reading the o2 sensor. In these older cars without heated O2 sensors, it took a few minutes before they would get up to operating temperature, so it was necessary to have a means of telling the computer when to switch over. The CTS also affects the ignition timing map as the computer adjusts the timing to match the engine's requirements based on temperature.

Now the problem is likely NOT the sensor itself. Rather, it is likely to be the wires on the harness at the plug have an internal break that is causing an intermittent fault to exist. You will need to fix the connector, not replace the sensor if you want to fix the issue. This is common on older computer controlled vehicles as wiring tends to deteriorate with time, especially under the hood. If you can get a pigtail with the connector on it and good wire coming off of it, don't use crimp connectors to install it. Rather, use solder and heat shrink tubing as it provides a much longer lasting connection.

 

[81Cutty]

The CTS is important because it tells the computer to run in closed loop and start reading the o2 sensor. In these older cars without heated O2 sensors, it took a few minutes before they would get up to operating temperature, so it was necessary to have a means of telling the computer when to switch over. The CTS also affects the ignition timing map as the computer adjusts the timing to match the engine's requirements based on temperature.

Now the problem is likely NOT the sensor itself. Rather, it is likely to be the wires on the harness at the plug have an internal break that is causing an intermittent fault to exist. You will need to fix the connector, not replace the sensor if you want to fix the issue. This is common on older computer controlled vehicles as wiring tends to deteriorate with time, especially under the hood. If you can get a pigtail with the connector on it and good wire coming off of it, don't use crimp connectors to install it. Rather, use solder and heat shrink tubing as it provides a much longer lasting connection.

It's only $17 at Autozone to buy a new sensor that comes with a good plug and wires. I know the sensor isn't bad because when you wiggle the plug it changes.

And yes, I plan on doing the proper way of connecting the new wires to the old wires. Plus, the correct way looks a lot better.

Thanks for all the help. 😀