I have a 1988 XJS Hess Esinhardt convertible 5.3 V12. Without letting the engine warm up to when heat gage starts to move, It will run about a mile then when you push hard on the acelerator it will totally shut off. When put in neutral and restarted it, runs fine and will not quit once it warms up. Replaced ECM, coil, plug and coil wires, injector wiring harness. Any suggestions?

 

My first guess is that the coolant temp sensor is inaccurate, telling the ECU that the engine is warmer than it is. The ECU responds by pulling back on the 'cold enrichment' fueling. On a carbureted engine it would be like pushing the choke knob in too soon.

The 'could be' list might get long. As guess go, the coolant temp sensor isn't painful in either cost or effort.

Cheers
DD

 

Thanks. I will have my mechanic check it out.

 

Does the AAV work as it should? This is the fast idle on startup gadget? If it is working properly the car should tickover from cold at about 1000 rpm after a few seconds.
Greg

 

Is the AAV the same as the "coolant temperature sensor"?
Sorry, I am not up on the terminology.

 

No.

The AAV (Auxiliary Air Valve) is a temperature sensitive mechanical device which allows more air into the engine so as to give a faster idle speed when the engine is cold.

The coolant temp sensor is an electronic sensor that feeds temperature information to the computer (ECU-electronic control unit). The ECU is the brains of the fuel injection system

Cheers
DD