Hi, I need some advice please. I have been trying to sort out the rough running problem on my car since I bought it from my uncle about 3 years ago. I have been doing a rolling restoration. My uncle had laid it up in 1995 after it failed it's MOT. The millage is 55000 miles. One thing it failed on was the Co levels . I know that was due to the AED unit which I have replaced but with a seconhand one.I got a home tune chap who came and checked the timing the plugs the compression.But at that time the AED unit was disconected as I had already warmed the car up before he came. One thing I have tried and don.t understand is if I take ignition lead 1 off while it's running you notice a difference as you would expect Also with 2/3.. But from 4/5/and 6 there does'nt seem to be a noticeable change.. I know that I would need a new AED unit. But I need to try and sort out the other problems first.
Any ideas, many thanks
Rough running series 2 4.2
Moderator:LJR
If removing the leads from 4, 5 and 6 (you know that on the XK engine 1 is at the back?) doesn't make a difference, it's possible that the carb supplying those cylinders is out of whack or the firing order is wrong. But the mobile tune man should have spotted that.
Check the leads coming off the distributor are connected in the right order (having regard to the back-to-front numbering system.)
Which year car is it and what carbs are fitted? Adjusting the HIF7 is different to the earlier models and the weak/rich screw appears to operate in the reverse sense in that you screw it in to richen the mixture (counter-intuitive, some find.)
Does it mis-fire if the AED is disconnected and the pipes from it plugged?
Check the leads coming off the distributor are connected in the right order (having regard to the back-to-front numbering system.)
Which year car is it and what carbs are fitted? Adjusting the HIF7 is different to the earlier models and the weak/rich screw appears to operate in the reverse sense in that you screw it in to richen the mixture (counter-intuitive, some find.)
Does it mis-fire if the AED is disconnected and the pipes from it plugged?
Al McL
'93 XJS 4.0 - '20 XF 2.0 Sportbrake
'93 XJS 4.0 - '20 XF 2.0 Sportbrake
The year is 1974 model with HIF8 carbs which I had refurbished.I am sure it ran better when I first drove it from my uncles house. It also had new leads new coil new ballast resistor. The firing order is correct on the cap. number 1 being at the back. timing 8 degrees BTC. I have checked each spark plug with one of those see through plugs and it is firing
many thanks
many thanks
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