QuestionHi,my problem is that every once a while driving in the 50 to 60 mile an hour the car gives a jerk sometime mild, other time real hard. At lower speeds it dosn't do it. It may a 100 to 200 miles an just when you get thinking its drove out of it. It does it to you. The car started doing this problem at around 143.000 Kms
Do have any suggestions as to what might be causeing this jerk. It does show any codes when garage checks out the computer.
Other than this and the normal repairs this car runs like a dream.
Your advise would be much appreciated
AnswerHi Syd,
It sounds like a misfire that happens rarely. If it were electrical it might be an intermittent failure of the spark coil, but only time will tell when/if it becomes more frequent. It might be a spark plug that is dirty or has too wide a gap. But that too would "progress" to become more frequent. On the fuel side it might be water condensation in the fuel tank that occasionally is drawn into the fuel pump and then momentarily causes a failure to ignite the mixture when injected. If you have a high humidity climate that could be the cause. Or a fuel filter that is occasionally obstructed for a moment might produce that effect.
Of course if it is an electrical intermittent, the possibilities of that are unlimited, you either have to be looking for it with a meter when it happens or the frequency or severity of the "mis" has to increase until you can detect it with an instrument without having to wait.
A last possibility is the ignition switch which might be flaking out. You can see if it feels like what you experience by turning it back from the run position for a moment, but not totally letting the engine die, to see if it feels like the phenomenon you experience at random.
Those are some possibilities to consider, but compare them to the service work that has been done to see if any of them might be applicable. I would only consider those that servicing might have overlooked.
Roland
