Excuse my basic knowledge of mechanics. My above vehicle has started running rough or "chugging". My mechanic cannot get it to throw a code but has replaced the back cylinders coils and spark plugs.This did not resolve the problem. He then suggested Cylinder 5 was not firing correctly. He has now arranged to have the fuel injectors cleaned. I have read elsewhere that the MAFS can cause these type of symptons but he claims to have cleaned this. You can actually smell petrol at times (running rich?). He seems to be at a loss as to the cause. Would a dealers computer analysis be superior to my local mechanics tool he plugs in beneath the dash? Any advice would be appreciated as I dont want to keep throwing money given the age of the car and its market value

 

might want to also do the front plugs and coils. maybe play with the old coils that came off the rear.

from my experience, when a coil goes bad I always see an ashy looking grayish spot towards the bottom of the coil on the rubber boot that goes over the spark plug.

 

Well I and the mechanic are baffled. 3 new coils and plugs in back row with 2 old coils (which included a newish one) moved to the front. 1 spare coil left. Engine still running rough and injector clean (independantly carried out and no problems noted) conducted. Original coil from cylinder 5 then removed from front and replaced with the spare. Voila, engine running like new again. It appears Cylinder 5 coil the problem all along so not sure why this was not picked up from the outset? Guess coil and plug replacement at rear probably not a bad investment with 226,000Ks on the clock. At least the front row can be accessed easier if and when required! Still an expensive exercise!
PS Thanks for your advice uptownsamcv it appears to have been spot on, especially playing with the old coils at front.

 

nice advice uptownsamcv