Restricted performance

[hector]

Update: 2 coil packs causing a misfire and a 3rd overheating! New packs ordered and new plugs fitted. This car has done 60K and is 18 years old so I am told that to renew all packs makes sense and the plugs are due to be renewed at that milage.

[J44EAG]

Two grades of plugs tend to be prominent on the market place. 60k or 90k miles lifed. I recall the genuine OE plugs are 60k lifed so your replacements are really to be expected.

Given age, then plugs do tend to become iffy after so many years in service. Misfiring plugs are guaranteed to wreck coil packs.

Plugs can fail well below the 60k service change. I`ve had that on both V6 and V8 Jaguar engines in the past. Realistically and in my opinion, a 50k change out is perhaps better given that plugs are relatively cheap whereas coils packs are not! It is quite normal on the V8 to find misfiring occurring at 1600 & 2300 RPM. Left in that condition for long enough, the coils on the offending cylinders are placed in immediate jeopardy. Caught early, a plug change is often enough to preclude coil failure. I`ve seen that a couple of times in the last thirteen years.

Best advice is obviously to buy the best quality plugs that you can afford. Cheap products are rarely reliable in the long term.

Mike K

[hector]

I have had my 308 back for a week or so coil packs and plugs replaced, took her for a couple of 40 mile runs. The improvement is fantastic so smooth and extra power, it looks like the fuel consumption has improved too. You don't realise over time how performance can deteriorate. Looking forward to the XJ event in Warwick.