Spark Plug Replacement
Also called plug change
Spark plugs ignite the fuel mixture. They wear as the gap widens, which makes starting harder, raises fuel consumption and eventually causes misfire. Cars running on CNG wear plugs faster and often need a different heat range. Old plugs are worth reading: oily, sooty or white plugs each point to a different engine condition. Replacing plugs restores clean ignition. It does not fix a coil fault, a blocked injector or low compression, though it makes those easier to identify.
Signs you need this
- Harder starting, especially on cold mornings
- Rough idle or a slight shake at a standstill
- Higher fuel consumption with no change in driving
- Hesitation when accelerating
- The plug replacement interval has been reached, or the car runs on CNG
Not all of these have to be present, and one of them on its own can mean something else entirely. That is what the diagnosis is for.
What the job includes
- Old plugs removed and read for wear, fouling and heat colour, cylinder by cylinder
- Correct plug type and heat range for your engine and fuel, including CNG
- Gap checked against specification before fitting
- Plug wells cleaned and checked for oil leaking past the seals
- Plugs torqued to specification, not over-tightened into the head
- Coil boots inspected and the engine road tested afterwards
How we do it
Confirm the right plug
Type, heat range and gap are matched to your engine and fuel, as CNG cars often need a different specification.
Remove and read
Plugs are removed in order and read, since their appearance shows how each cylinder has been running.
Check the wells
Plug wells are checked for oil, because oil sitting around a plug destroys coils and causes repeat misfires.
Gap and torque
Each new plug is gap checked and torqued to specification, which protects the threads in an aluminium head.
Test and report
The engine is run and road tested, and we tell you what the old plugs indicated about engine condition.
How we work
The same on every job, which is why we can write it down.
Diagnosis before quote
We find the fault first. A price given over the phone for a noise nobody has heard is a guess.
The price is agreed first
You approve the work and the cost before a spanner is picked up. Extra work means another call.
Parts you can check
We tell you whether a part is genuine, OEM, aftermarket or used, and what each one costs.
Old parts returned
Ask and we will hand back whatever we replaced. It is the simplest proof that the job was done.
Book spark plug replacement
Fill this in and a person will call you back to confirm the time and the price. Only your name and one way to reach you are required.
You send this
Takes a minute. No payment, no obligation.
We call you
To confirm the car, the time and the location.
Tell us the car and the symptom
We will arrange a mechanic at your location, or a slot at the nearest workshop. No payment until the price is agreed.