Hello again,

I've random and cylinder 1 misfire issue. I've already replaced the battery and spark plugs. To try I've reverse ignition coil 1 and 2.

Thx
yA

 

How many mils?

 

43000 miles but I don't know if the mileage is correct.

 

Are you able to monitor fuel trims? I know you can on USA market cars, I am guessing this is a European market car? If fuel trim is positive numbers, adding fuel, I would suspect a restricted fuel injector in #1.
Did you test compression when the spark plugs were out? It would be good to check, low compression usually gives a misfire at idle only, to begin with.

 

My XJS is coming from the States :-) I have a nice OBD scanner I'll check fuel trims.

Question, the exhaust downpipe has a leak but I need a lift. According to what I've read about fuel trims, by using oxygen sensors the computer compensate permanently the percentage of fuel through injectors. I suppose that I should replace the exhaust first!

 

"Question, the exhaust downpipe has a leak but I need a lift. According to what I've read about fuel trims, by using oxygen sensors the computer compensate permanently the percentage of fuel through injectors. I suppose that I should replace the exhaust first!"

The leak is probably affecting the exhaust sensors and their output to the ecu. Fix the leak and I bet your problem will be resolved.

 

I am going to try SEAFOAM on mine...
I have a 100000 mile on mine now...


you might want to check seafoam out...

 

Sensor 1 Bank 1



Sensor 1 Bank 2



Sensor 2 Bank 1



Sensor 2 Bank 2 Not present !?

Fuel trim

 

Seafoam is nothing more than a mixture of oil, naptha and rubbing alcohol. Nothing there that will fix any problems on a modern engine.

 

I am not familiar with the 4.0, but I would have assumed an inline 6 would have one precat O2 sensor and one post cat O2 sensor. Is the exhaust split into 2 sections off the engine, with 2 pre and 2 post catalyst O2 sensors? I see that bank 1 is pulling away a lot of fuel, 10% long term, and 20+% short term. Since #1 is misfiring, and I assume this is part of what is identified an bank 1, I still am suspecting #1 fuel injector.
For what it is worth, I know a lot about emissions controls and engines in general, I know quite a bit about early XJ-S V-12's, I know almost nothing about later XJS 6 cylinders.