Here's a video: https://youtu.be/wYyaW9wRt6U

For a couple of months now my car has had a rough idle and shudders while accelerating - Vauxhall Astra J Exclusiv MK6, 4 years old 61k miles spark plugs done last year.

It starts off shuddering if I accelerate from too high of a gear (low RPMs) and then it progressively gets worse and happens even when in mid-high RPMs to the point where I would be on motorway at a steady 70 mph and still feel faint shudders. I guess as the car gets warmer it just gets much more noticeable.

A colleague told me to the clean throttle body which I did. I didn't notice any huge deposits just some oily grime around the walls and butterfly valve. Unfortunately cleaning this made no difference.

A local garage said they couldn't find the problem and advised me to go Vauxhall dealership which I want to avoid for now.

What's changed since a couple of months ago? I serviced the car myself (air + cabin filters and oil) in September.

For all you mechanically minded people out there, I would appreciate some things I could look into!


OBD trouble code P0301. Which for the "GM" section shows quite a long list of troubles. The problem has worsened over last 48 hours, it is idling is now very rough even from cold and with emissions control system (flashing amber) + electronic stability control (constant amber) on dashboard. Is there something here where I can read between the lines to remedy from home?

  • 1
    Are there any CEL codes? If you are talking about the ticking/shudder, it sounds almost like this is causing the computer to pull timing due to it coming through like a ping/knock. The ticking sounds more prevalent at the back side of the engine (where the intake is at). This could be a bad injector, which could also be the source of the issue. Hard to tell with just the video. Commented Dec 24, 2016 at 16:08
  • @Pᴀᴜʟsᴛᴇʀ2 I haven't got OBD code reader, I'll order one. When you say "bad injector", can I assume you mean fuel injector? If so, I'll look up in Haynes how easy it is to do myself it might be worth a shot.
    – codaamok
    Commented Dec 24, 2016 at 16:24
  • Do you remember the onset of the problem? It might be relevant to know if the problem "crept up on you" or if the onset was more sudden and noticeable.
    – dlu
    Commented Dec 24, 2016 at 16:30
  • Before you go changing out any parts, you really need to localize where the problem is stemming from. The ticking noise followed by the engine stumble is very noticeable. Get yourself an automotive stethoscope and localize where the sound is emanating from. From the video, this should be very easy to figure out and localize. If you cannot get or cannot afford a stethoscope, you can use a long screwdriver, placing the handle end against your ear, then touching the tip to various parts. Just be careful of the moving parts as you do this. Commented Dec 24, 2016 at 17:09
  • @Pᴀᴜʟsᴛᴇʀ2 Thanks, great advice "stop buying parts and start diagnosing" - if I manage to localise it, if I picture the unit/area, would you still be happy to help if replied back here? This may be some time after the holidays.
    – codaamok
    Commented Dec 24, 2016 at 17:51

3 Answers 3


I don't know that particular car well, but maybe a vacuum leak? Perhaps it's at the intake manifold, and worsening as the parts warm up, expand, and mating surfaces change shape?

  • 2
    Welcome! Thank you for contributing your thinking and experience here. If you can it would be great if you fleshed your answer out with some more information. Can you add any advice on how to test for a vacuum leak? Or where specifically to look? That would probably make the answer more useful both to this problem and for others with similar problems. Thanks again!
    – dlu
    Commented Dec 24, 2016 at 16:09

I can't quite hear the clicking properly but check your ignition leads.. If I'm hearing right it sounds like a plug lead or coil pack is arcing somewhere and its timed with the uneven idle too. Have a look around the ignition leads & spark plug areas if possible in the dark, you may be able to see arcing somewhere if that's what it is.

You'll likely be better guided once you receive the OBD tool & can read the codes, assuming the miss has been picked up buy the sensors.

EDIT... So the OBD tool has pointed towards a cylinder 1 misfire (P030'1')

I think just to rule out anything major I would be doing a compression check next on that cylinder, although a check on all cylinder pressures would be good practice. If cylinder pressures are ok, then I would still be considering the ignition system, especially as you suggest the issue seems to get worse as the engine warms up and is put under load. A plug, coil pack etc would exhibit this behaviour. Although there is always the chance of an electrical fault or ECM issue before these points.

Going forward I would perhaps advise that if you are not particularly versed in testing procedures etc that you perhaps consider whether or not to let a diagnostics technician or main dealer take a look at this fault. I only say that as... We will all try to guide you but at the end of the day these issues need fixing sooner rather than later, especially if you're using the vehicle. As depending on the misfire rate and driving conditions etc, un-burnt fuel from the misfire actually gets into the exhaust and can damage the catalytic converter too which would be more cost. This is born out by the now displayed emissions control warning lamp.

At least if you opt to have an experienced dealer technician look at the car he will have access to far better diagnostic equipment & parts too. Plus may have even experienced the same thing on the same model before so knows the signs. Although cost is always a factor here, a speedy repair may save you money overall.

  • Would ignition leads be called something else in the Haynes world? I see no section for it in the index for my car. There is this sentence "The ignition module consists of four ignition coils, one per cylinder, in one casing mounted directly above the spark plugs. This module eliminates the need for any HT leads as the coils locate directly onto the relevant spark plug".
    – codaamok
    Commented Dec 25, 2016 at 13:25
  • Sorry.. My terminology is from old school.. As you have no leads. The coil packs are attached directly or indirectly to the plugs.. These can and do fail though in a similar manner to leads either due to internal failure or high voltage breakdown via their plug caps which may start to arc around the plug sleeve. This is harder to see though as the plug connections/boots are normally shrouded or are obscured from sight. The OBD reader should point you in the right direction.. Unless you experienced in disconnecting each coil connector separately to try & trace the firing imbalance.
    – Orb
    Commented Dec 25, 2016 at 13:41
  • Thanks, I'll wait until OBD arrives. The ignition module is bolted directly on top of the spark plugs.
    – codaamok
    Commented Dec 25, 2016 at 14:49
  • Hi Orb, hope you had good xmas. I've updated question to include OBD info, your help would be great
    – codaamok
    Commented Dec 29, 2016 at 15:25

Hi I had the same problem vehicle shutters when warm up answer is replace plugs and coil pack and faulty injectot cost around 145. 00 for all put iridium plugs better firing plug and your problem will disappear good luck easy to do

  • Thanks, the problem was a misfiring cylinder so I replaced the coilpack and spark plug.
    – codaamok
    Commented Aug 13, 2019 at 11:21

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .