Vauxhall Z19DTH 1.9 CDTi 150hp Injector Problems: Symptoms & Repair (UK)

The Z19DTH is a Fiat-sourced 1.9 CDTi engine used across Vauxhall's range. Found in the Vectra C, Astra H, Signum, and Zafira B, it uses Bosch solenoid injectors. The 150hp version is the most common in the UK and injector failures are well-documented.

Common Z19DTH injector failure symptoms

• Rough idle and vibration: Injector imbalance causes the engine to run unevenly at idle.
• Black smoke under acceleration: Over-fuelling from worn nozzles.
• Loss of power: The ECU limits output when injector deviation is detected.
• Diesel smell from engine bay: External leaks at injector seals.

Why Z19DTH injectors fail

• fuel contamination
• high-pressure wear cycles
• carbon buildup
• poor fuel quality
• internal valve wear

How to diagnose Z19DTH injector faults

1. Read fault codes: Connect an OBD-II scanner and note any injector-related codes (P0201–P0204, P2146, P2149). This identifies which cylinder is affected.
2. Perform a leak-off test: Disconnect the fuel return pipes and route into measuring containers. Run the engine at idle for 60 seconds. Compare volumes per cylinder against manufacturer spec.
3. Listen for injector tick: Use a mechanic's stethoscope on each injector body. A dead or irregular tick indicates a stuck or failing solenoid.
4. Check fuel rail pressure: Monitor live fuel rail pressure data via diagnostic tool. Low pressure can mimic injector symptoms and may indicate a fuel pump issue instead.
5. Inspect for external leaks: Check around injector seals for signs of fuel or combustion gas leakage. Black carbon deposits indicate a blown seal.
6. Cylinder balance test: Use diagnostic software to run a cylinder contribution test. This electronically disables each injector in turn to measure its effect on engine speed.

Fault codes linked to Z19DTH injector issues

• P0201-P0204 – Injector circuit malfunction
• P0087 – Fuel rail pressure too low

Z19DTH repair advice

The Z19DTH uses Bosch solenoid injectors. IMA coding is required via Tech2 or compatible tool. The same injectors are used in Saab 9-3 and Alfa Romeo 159 versions.

Z19DTH injector replacement cost (UK)

• Per injector: £180 - £350
• Full set: £700 - £1,200
• Labour: £120 - £300

Compatible injector part numbers for Z19DTH

• Bosch 0445110276 – Bosch injector for Z19DTH 150hp
• Bosch 0445110159 – Bosch injector for Z19DTJ 120hp
• Vauxhall 55200259 – Vauxhall OE reference

Vehicles using the Z19DTH engine

• Vauxhall Vectra C (2004-2008)
• Vauxhall Astra H (2004-2010)
• Vauxhall Zafira B (2005-2011)
• Saab 9-3 (2004-2012)
• Alfa Romeo 159 (2005-2011)

Find your exact Z19DTH injector by registration

Frequently asked questions

Is the Saab 1.9 TiD the same engine as the Vauxhall 1.9 CDTi?

Yes. The Saab 9-3 1.9 TiD uses the identical Z19DTH engine with the same Bosch injectors.

How much does Z19DTH injector replacement cost?

A set of four costs £350-£600. Labour is 2-3 hours.

Do Z19DTH injectors need coding?

Yes. IMA coding via Vauxhall Tech2, MDI, or compatible diagnostic tool is required.

How much does it cost to replace injectors?

Replacement typically costs £150–£350 per injector depending on brand and engine. A full set of four with professional fitting usually costs £600–£1,200.

Can I drive with a faulty injector?

Driving with a faulty injector can cause engine damage, increased fuel consumption, DPF contamination, and oil dilution. We recommend diagnosis and replacement as soon as possible.

Do new injectors need coding?

Some vehicles require injector coding after replacement using manufacturer-specific diagnostic tools. Many Bosch solenoid units are plug and play. Check your engine guide for specific requirements.