Rough idle/missing

XJ
1

I have a rough idle/missing issue with my 1979 XJ6L. (Vin JAVLN49C101207)
Done so far:
New plugs, plug wires, rotor, distributor cap, coil, fuel filter, injectors cleaned, tanks flushed, replaced ECM.
Note: coil gets extremely hot to the touch.
It’s better, but far from smooth. Any suggestions? Thanks

2

hot coil? what temp is your extremely? is the coil you replaced match the original in specs or close to?..easy to test

3

It is direct replacement according to supplier. I have no means test it. Coil I replaced also felt hot to the touch.

4

any type of thermometer will check temp, little laser type are good, they do get warm so a reading would be helpful, if you have access to a multi meter you can test the coil Ohms, supplier?..
out of curiosity, were you advised to or had deemed all those items you replaced - to be faulty?

5

I recently bought the car and was trying to solve the issue and was advised by a foreign car specialist mechanic to make the changes. More about possible needs since the car had been sitting for a while, and perhaps fixing the problem. It’s a 79 with 99,000 miles. According to po engine n trans were rebuilt, and that appears to be true.

6

Verify that the cap, rotor and plug wires are all in good shape, and the plug wires are all in the correct order. if all is correct, check your fuel rail pressure, or be sure of the relief valve function.

7

The first step is certainly a compression test, dry and wet, Oldcat - to verify that the engine itself is not the cause. Easily done - and conclusive…

The coil will inevitably be hot; coil current averaging around 2A gives some 25W heat effect - and the coil is not that big…

Two simple checks; verify that the white wires are connected to coil ‘+’ the other 3 to coil ‘-’. And measure coil resistance by disconnecting coil ‘+’ and measure between ‘+’ and ‘-’…

Frank
xj6 85 Sov Europe (UK/NZ)

8

Thanks for the input. I have solved the problem (for me) I sold the car.

9

I have solved the problem (for me). I sold the car. Thanks for the input,

1 Like
10

A very effective solution indeed…!!