MajorCommonEngine

Mazda MX-5: P5-VPS SKYACTIV-G Intake Valve Carbon Buildup

P5-VPS SKYACTIV-G Intake Valve Carbon Buildup is a common engine fault on the Mazda MX-5 on the 2015 onward cars, and we rate it major. Putting it right costs $700 to $1,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 26 documented faults on the Mazda MX-5.

Vehicle: Mazda MX-5
Engine: P5-VPS
Years: 2015 onward
Fuel: petrol
System: Engine

This page covers the Mazda MX-5 as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mazda MX-5 faults26 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the Intake manifold or PCV / oil separator yet. We would rather show none than show a picture of a different part.

What goes wrong

The P5-VPS SKYACTIV-G 2.0L engine uses gasoline direct injection, meaning fuel is never sprayed across the intake valves and cannot wash away PCV oil vapour deposits. Over time carbon accumulates on intake valve heads and stems, restricting airflow into the combustion chamber. Above 80,000-120,000 km the deposit layer becomes significant enough to cause rough idle, hesitation on acceleration, misfires under load, and measurable reduction in power output. Correction requires walnut blasting or manual cleaning with the intake manifold removed.

What you would notice

Rough or lumpy idle at operating temperature
Hesitation or stumble on initial throttle application
Reduced power and throttle response above 100,000 km
Increased fuel consumption
Occasional misfires under moderate to hard load

How to check it

Where to look. Intake valves, intake ports, cylinder head inlet side

Confirm mileage and ask whether an intake cleaning service has been performed.
Check for rough cold idle and hesitation during a test drive.
If a workshop inspection is possible: Use a borescope through the intake ports or spark plug apertures to inspect intake valve faces and stems for carbon deposit accumulation.

Parts involved: Intake manifold, PCV / oil separator.

What it costs to put right

$700 to $1,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has an intake valve walnut blast or manual clean ever been performed?”
“Has an oil catch can been fitted to reduce PCV oil vapour?”
“What is the current mileage and full service history?”

Now check the Mazda MX-5 you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Mazda MX-5 buyer questions

Is p5-vps skyactiv-g intake valve carbon buildup serious on a Mazda MX-5?

We rate it major and common on the Mazda MX-5. The P5-VPS SKYACTIV-G 2.0L engine uses gasoline direct injection, meaning fuel is never sprayed across the intake valves and cannot wash away PCV oil vapour deposits. Over time carbon accumulates on intake valve heads and stems, restricting airflow into the combustion chamber. Above 80,000-120,000 km the deposit layer becomes significant enough to cause rough idle, hesitation on acceleration, misfires under load, and measurable reduction in power output. Correction requires walnut blasting or manual cleaning with the intake manifold removed.

How much does it cost to fix on a Mazda MX-5?

$700 to $1,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mazda MX-5 years are affected?

Our research records this fault on the 2015 onward Mazda MX-5. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Confirm mileage and ask whether an intake cleaning service has been performed. Check for rough cold idle and hesitation during a test drive. If a workshop inspection is possible: Use a borescope through the intake ports or spark plug apertures to inspect intake valve faces and stems for carbon deposit accumulation. Look here: Intake valves, intake ports, cylinder head inlet side