Engine flush and oil drain nut

[oakdale]

liner33 said:

The juddering is unlikely to be anything related to the spark plugs and/or fuel

Does the car have an egr system ?

As to whether its especially sluggish i guess you need to let someone with experience of them to drive it and confirm

Low throttle or coasting juddering is often related to closed up plug gaps in my experience.

[liner33]

oakdale said:

Low throttle or coasting juddering is often related to closed up plug gaps in my experience.

On four electrode plugs? If those are bent its new plugs time

[oakdale]

liner33 said:

oakdale said:

Low throttle or coasting juddering is often related to closed up plug gaps in my experience.

On four electrode plugs? If those are bent its new plugs time

Not sure what you mean but if one earth electrode is bent towards the centre electrode, only that one will spark (because electricity takes the path of least resistance) and it will be a poor spark.

[Chris32345]

liner33 said:

On four electrode plugs? If those are bent its new plugs time

On a lot of moderne plugs it is especially any sort of iridium or other ultra thin electrode plugs that most modern engines use

[captain.scarlet]

Thanks everyone.

Looks like if is the plugs then it'll be easier to just get all of them changed. Chances are there'll be plenty of oil in there from before needing to be wiped.

It's not a nice ride to have the juddering even if it's slightly faint at times.

Takes me on to another observation...a hissing sound on acceleration between certain speeds (20 to 30 mph) and/or revs. Not there at idle and it will go if I release the throttle or simply exceed a certain speed.

Possible air intake issue?

No coincidence this has come with the recent rocker gasket change! One thing cured, another broken.

[Athlon]

Two things on those engines if it is the one with the coil pack down the centre with a cover over it.
First is the coil pack, they are rubbish and fail often, this however usually brings the check light on.
Second is the breather system which is built into the rocker cover itself, run the engine and try taking the oil cap off, if it is really bad the vacuum will make it really difficult to get it off, or remove the dipstick and listen for the engine taking a gasp of air into the crankcase as the vacuum is released

[oakdale]

captain.scarlet said:

Thanks everyone.

Looks like if is the plugs then it'll be easier to just get all of them changed. Chances are there'll be plenty of oil in there from before needing to be wiped.

It's not a nice ride to have the juddering even if it's slightly faint at times.

Takes me on to another observation...a hissing sound on acceleration between certain speeds (20 to 30 mph) and/or revs. Not there at idle and it will go if I release the throttle or simply exceed a certain speed.

Possible air intake issue?

No coincidence this has come with the recent rocker gasket change! One thing cured, another broken.

I mentioned plugs as a possibility but i wouldn't change them until you've looked at them, I think you need to find the cause of the hissing sound first because an air leak will also cause the problem you're having.

Why not get the mechanic who did the job to look at it again? It's clearly not right since he worked on.

[liner33]

oakdale said:

Not sure what you mean but if one earth electrode is bent towards the centre electrode, only that one will spark (because electricity takes the path of least resistance) and it will be a poor spark.

yes and more likely to be misfiring under load rather than idle

The spark will ALWAYS take the path of least resistance and irrespective of the number of electrodes only one is ever used, its a misconception that four electrodes = four sparks

[captain.scarlet]

liner33 said:

oakdale said:

Not sure what you mean but if one earth electrode is bent towards the centre electrode, only that one will spark (because electricity takes the path of least resistance) and it will be a poor spark.

yes and more likely to be misfiring under load rather than idle

The spark will ALWAYS take the path of least resistance and irrespective of the number of electrodes only one is ever used, its a misconception that four electrodes = four sparks

Afternoon, Gents.

Thank you all for the suggestions.

Apologies I've not responded sooner. I only finally got round to taking some further action.

As far as taking it back to the mechanic who changed the rocker gasket is concerned, in typical fashion he couldn't find anything wrong with it, "your engine runs beautifully", another mechanic whom I know took it for a spin around the block and again it was a classic "didn't feel anything".

That said, we ran a diagnostics check despite there being no EML. Found a faulty AC pressure switch (changed and regassed yesterday but alas no AC on the hottest of days) and error code for the thermostat, which I'll replace once I get some new torx bits. Annoyed there's no AC and they insisted I keep the gas! The mechanic when taking the car into the bay did notice the misfire - especially worse at low speeds and slowing down.



I did check the spark plugs - they're only a month or so old and so hardly used (no more than 40 miles covered), but they had already accumulated what looks like soot.

Surely that indicates a bad air-fuel mix?


Little or no oil on them compared with when I first changed them, so the rocker gasket has sure cured that.


I do have replacement plugs in case these were dropped, but given there is no EML on and fuel economy has been exceptionally poor - just shy of a full tank on a 1.6 Ecotec petrol and the range is apparently 219 miles (!!!!) - I am toying with the idea of changing the camshaft sensor and possibly the lamda sensors.


That's before considering any PCV or EGR valve.

As for the rattle/hiss, it seems to occur when wanting to accelerate heavily, usually in 3rd gear, and only for a limited number of mph or revs. I'm starting to think it may be something loose underneath like a heat shield but the timing of the rocker gasket change is a bit coincidental.

Thanks again.