MajorCommonEngine

Mazda CX-5: SKYACTIV-G Intake Valve Carbon Deposits

SKYACTIV-G Intake Valve Carbon Deposits is a common engine fault on the Mazda CX-5 on the 2012 onward cars, and we rate it major. Putting it right costs $700 to $1,800 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 36 documented faults on the Mazda CX-5.

Vehicle: Mazda CX-5
Engine: 2.0L / 2.5L
Years: 2012 onward
Fuel: petrol
System: Engine

This page covers the Mazda CX-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 CX-5 faults36 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 SKYACTIV-G 2.0-litre (PE-VPS) and 2.5-litre (PY-VPS) engines use direct injection exclusively, meaning fuel is never sprayed across intake valve stems. Without the cleaning effect of port-injected fuel, oil vapours from the PCV system condense on the back of intake valves and accumulate as hard carbonaceous deposits over time. By 80,000-120,000 km the deposits can reduce effective valve curtain area by 30-50%, causing rough idle, loss of power at high rpm, misfires under load, and cold-start hesitation. Removal requires walnut blasting or manual scraping with the intake manifold off, as chemical cleaners cannot penetrate baked carbon on the valve stems.

What you would notice

Rough idle particularly when cold
Hesitation or stumble on acceleration from low rpm
Misfires or rough running above 4500 rpm
Cold-start hesitation lasting more than 10 seconds
Slightly elevated fuel consumption
Occasional P0300-series misfire codes

How to check it

Where to look. Intake valve stems and heads, accessible via intake port with manifold removed

Watch for: Rough idle particularly when cold. If a workshop inspection is possible: Inspect intake valve stems and heads through intake ports using an endoscope; carbon deposit thickness on valve stem backs should be assessed — deposits exceeding 2-3mm indicate cleaning is overdue; check PCV hose condition as a blocked or leaking PCV worsens deposit rate; review service history for any record of intake valve cleaning.

Parts involved: Intake manifold, PCV / oil separator.

What it costs to put right

$700 to $1,800 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 the intake valves ever been cleaned by walnut blasting or chemical treatment?”
“Any history of rough idle or cold-start hesitation?”
“What is the current odometer reading and has the vehicle exceeded 80,000 km?”

Now check the Mazda CX-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 CX-5 buyer questions

Is skyactiv-g intake valve carbon deposits serious on a Mazda CX-5?

We rate it major and common on the Mazda CX-5. The SKYACTIV-G 2.0-litre (PE-VPS) and 2.5-litre (PY-VPS) engines use direct injection exclusively, meaning fuel is never sprayed across intake valve stems. Without the cleaning effect of port-injected fuel, oil vapours from the PCV system condense on the back of intake valves and accumulate as hard carbonaceous deposits over time. By 80,000-120,000 km the deposits can reduce effective valve curtain area by 30-50%, causing rough idle, loss of power at high rpm, misfires under load, and cold-start hesitation. Removal requires walnut blasting or manual scraping with the intake manifold off, as chemical cleaners cannot penetrate baked carbon on the valve stems.

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

$700 to $1,800 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 CX-5 years are affected?

Our research records this fault on the 2012 onward Mazda CX-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.