If your XJ’s etc. does not respond till it warms up or schackes the engine
till it warms up you might try replacing the Thermo time on the intake
manifold or the water temp. sender hooked up to the computer.
I have those items advertised in the classified section of this forum.
Long time member of this forum Walter![20210210_091305|281x500](upload://yxuYtmXOV4rCy1dnq5tcrbnMEMQ.jpeg)