Hesitation

[kmorrison2011279]

Hi all, I have a funny & random kind of hesitation that I need to investigate!
It happens out of the blue when I'm cruising at 50-60mph or when I'm accelerating mainly when the engine is up to temperature
when it happens there's a slight vibration & drone kind of noise, if I take my foot off the accelerator then put it back down it clears itself some times I can accelerate and drive through it other times not.
I thought it could be the prop shaft with the vibration noise but it looks & feels fine! I have checked every coil on each spark plug but all is good there. as yet I haven't replaced the plugs but that's the next thing on the list! then maybe do a complete engine service including air fuel & oil filter.
Should there be anything else to look out for?
The car is a 1997 X300 with less than 70k on the clock

[J44EAG]

Throttle body sludge is often a problem. Crank case breather residue fouls the throttle body throat and butterfly plate. You might also find any small bore rubber pressure or vac hoses are breaking up and need replacement. Both of these faults can affect idle and pick up. I suggest you go to a main dealer or a company such as Manners or Barretts and order new pipes and a throttle body gasket before you start the job. Use rubber gloves or you will quickly get mired in sludge!

At this mileage you may also begin to see camshaft position sensor break down. Worth getting a sensor as a spare in case of future issues. The sensor is on the top front of the engine and is easily changed.

Probably not presently an issue but the cylinder head temp sensor can also begin to fail due to age and mileage. Again it is a simple one to change......fitting a new thermostat is also worth doing whilst in the area.

A bit of basic maintenance needed here before ploughing in deep.

Mike K

[kmorrison2011279]

Thanks for your reply Mike, I will indeed do what you suggest and see where we go from there, will be back with an update soon
Keith

[kmorrison2011279]

Throttle body sludge is often a problem. Crank case breather residue fouls the throttle body throat and butterfly plate. You might also find any small bore rubber pressure or vac hoses are breaking up and need replacement. Both of these faults can affect idle and pick up. I suggest you go to a main dealer or a company such as Manners or Barretts and order new pipes and a throttle body gasket before you start the job. Use rubber gloves or you will quickly get mired in sludge!

At this mileage you may also begin to see camshaft position sensor break down. Worth getting a sensor as a spare in case of future issues. The sensor is on the top front of the engine and is easily changed.

Probably not presently an issue but the cylinder head temp sensor can also begin to fail due to age and mileage. Again it is a simple one to change......fitting a new thermostat is also worth doing whilst in the area.

A bit of basic maintenance needed here before ploughing in deep.

Mike K

Update, replaced all 6 plugs & coils & camshaft position sensor plus added a litre of injector cleaner = misfire gone, I suspect the crankshaft position sensor was the culprit as it looked like it was the original one.
thanks for all help

[ptjs1]

Keith,

Well done for sorting the problem! Just as a matter of interest, did you change the crankshaft position sensor, or the camshaft position sensor (known as the engine position sensor on these AJ16 engines)? My guess is that you changed the crank position sensor as the camshaft or engine position sensor doesn't do anything on these engines once the engine has started?

Paul