[DrDave]

When its running good (which USED to be most the time), the car runs perfectly, and starts in less than 1 second. However now, at random, the engine completely STALLS while driving, and is then sometimes hard to start. I managed to check the sensor readings once while it was acting up, and found that the coolant sensor was reading LOW (52) while the manifold air temp sensor (MAT) was reading normal (about 100). The newish O2 sensor was also reading low (17-18, which I believe is lean?), but now seems to be fine again. Normally, I would think it was a bad coolant sensor or something, since it's usually pretty close to the MAT's value.

However, the coolant sensor has since started reading normally as well (until it dies out, when it's probably reading 52 again).

Do these types of sensors fail completely, or is it possible to fail sometimes (stay around 52), and then other times act normal (read 90-100 again)?

Does this have any relation to the O2 sensor? Could it be bad wiring?

Help!!

 

[thu]

What codes are stored?

 

[DrDave]

There are NO codes stored. It was running beautifully before this intermittent problem came up--and now its happening more frequently. Could the wiring cause this, or is it possible it's the sensor?

I'm not sure if coolant sensors fail completely or if they can 'intermittently' fail. Anyone who knows would be of great help...

 

[100]

This is just my guess, but I think the coolant temperature sensor is a resistance-sensor, which changes its resistance as temperature changes (at least my 4.9 has that type of sensor). If so, bad wires (like Cu conductor inside the wire is about to break) may result temporary open circuit, causing the sensor to read either its maximum or minimum values. Or bad insulator may result temporary short circuit, resulting in the same thing. This may be in the sensor, but could happen anywhere along the lead wires.

You could remove the sensor and connect to the ohm meter while you heat up the sensor and see how the resistance changes. If it show erratic behavior, the sensor is in bad shape.

Good luck!

 

[adalla]

Yeah... the sensor is right by the thermostat on 4.9. I do not know about your engine though. I would play with wires, connector etc.

 

[DrDave]

Hmm.. if I wanted to re-wire everything under the hood, does anyone know what that would involve with the center/LH/RH bulk-heads? What do those connectors look like?

I've never taken one of those bulkheads off, but I don't want to disturb them until I'm planning to rewire them.

Any thoughts?

 

[Brix]

Can anyone please tell me where the coolant temp sensor on my 4.1 is on my '85 deville? I haven't got a clue. Neither of my manuals tell me where to look. Please!!!! Help!!!!:worship:


-Brix