Air temp sensor on left air intake snorkle reads the correct resistance across various temperatures. Ohms range is 960 with very cold air to 80 with very hot air. I am gauging pretty close with MM.

If I plug the connector in when cold the engine gets lumpy. If I plug the connector in when warm the engine falters and dies. So I run without it plugged in and it's "fine".

However, I note across the engine temperature range sweet spots and some not so sweet spots, mainly in acceleration from a cruise speed.

I don't understand how sensor inputs work. Are 12 V sent through the sensor and the "box" determines degradation and trims injector pulse width?

I have a feeling there could be connection/continuity issues or perhaps even box issues.

If both lines go the brain box I can check continuity at least? Is this correct?

The air temp sensor works with the MAP and coolant temp sensor. The manual says the air temp sensor is not be be viewed as a control device. More like a fine tuning device. So if everything is correct, it could (should) not stall the car.

 

First take into consideration that I'm not too familiar with the earlier, "Pre-HE" systems.

That said, on the HE models, it is common to mix-up the air temp sensor connector and the coolant temp sensor connector. The sensors reside in the same neighborhood, have the same type of connector, and the wiring is long enough to reach either one....and thus possible mix-up. Weird things happen when they're incorrectly connected. Just something to think about

Yes, continuity and resistance of the wiring from the sensors to the ECU can be checked. Do you have a good diagram? One that shows the pin locations at the ECU connector?

Cheers
DD

 

You are dead right on the location issue. They both come out of the same loom and are the exact same length and size. I do see little white bands on them. One says air. One says water. Seems ok.

I have the Series 3 factory manual but there are comprehensive sections on the older 12 cylinder in it. There is a small 2 1/2" X 3 1/2" diagram of the digital fuel injection system and pin-outs to the ECU. I would not call it good but I can make the numbers out, so it's functional.

I'll do some grunt work and post what I find.

 

Well the Series 3 manual diagram is a "6CU" ECU and my 77 has the "3CU" ECU.

I did find a much better (and correct) diagram on the AJ6 engineering website.

Now I can do some testing.

JAGUAR V12 FUEL INJECTION 1975-1980 - D Jetronic / AJ6 Engineering

 

Well, the testing proved that a husky guy can easily fit into the trunk.

Good continuity to the correct female terminals and the box does not smell like cooked electronics inside.

Was worth a shot. Thanks, Doug.