Rough running is easy to put up with. You get used to the shudder, you press the accelerator a bit harder, and after a while it just feels like the car’s age.
One of our customers had done exactly that with their 2007 BMW 325i. They booked it in for a minor service and mentioned, almost as an afterthought, that it wasn’t running as smoothly as it should.
The scan told us more than the service would have
I plugged the scan tool in before doing anything else. Several cylinders were misfiring.
A misfire means a cylinder isn’t burning its fuel properly. Owners notice it as roughness or hesitation, or just a car that’s lost its edge. The check engine light might come on. It might not. Plenty of cars run like this for months with nothing on the dash.
This engine has a separate ignition coil sitting on each spark plug. Six cylinders, six coils, six plugs. Heat and age wear them down, and a 2007 car has had plenty of both.
Six coils, six plugs
We replaced all of them. The customer approved the job before we started, and once it was done, the codes cleared, and the car ran properly.
Some mechanics would replace only the coils the scan flagged. I’d rather not on a car this age. The ones that haven’t failed are the same age and have covered the same kilometres, so you’re likely to be back for the next one soon.
But I’ll admit the scan pointed at several cylinders, not all six. Replacing everything was a judgement call, and it costs more on the day. This customer was happy to go ahead.
Why not just keep driving it?
You can, for a while. It gets expensive. Unburnt fuel goes into the exhaust, and a catalytic converter costs far more than a set of coils and plugs.
Guessing is the other expensive option. On a European car, swapping parts and hoping is a great way to spend a lot of money and fix nothing. A scan tells you which cylinder and which part it is.
What to watch for
- A rough idle at the lights
- Hesitation when you put your foot down
- A check engine light, especially a flashing one (if it’s flashing, stop driving and call us)
- Shuddering on a cold start that eases as the engine warms up
The RAC has a short note on car shuddering and misfires if you’d like a second source.
If your car feels off
Tell us what it’s doing, even if it seems minor. We can include a diagnostic scan with a car service, and if the scan flags something, you’ll get a quote for the repair before we touch a spanner.
We work across Parramatta, Castle Hill, Epping, Carlingford, Ryde and nearby suburbs. Contact us or call 0410 492 110. If your rego is due, ask about a mobile pink slip at the same visit.
FAQs
What does an engine misfire feel like?
Usually, it feels like a rough idle, hesitation under acceleration, or a flat feeling when you press the gas. Some misfires don’t trigger a check engine light at all.
Can I keep driving with a misfire?
A short trip to get it checked is usually fine. Weeks or months isn’t, because unburnt fuel can damage the catalytic converter. If the check engine light is flashing, stop driving and call a mechanic.
Do you need to replace every ignition coil at once?
Not always. It depends on the car’s age and how many cylinders are affected. On this 2007 BMW, we replaced all six.
Do you work on European cars?
Yes. We service and repair European and Australian vehicles.
