Infiniti G35 Firing Order : VQ35DE & VQ35HR – Complete Technical Reference
🔧 2. Why Does the G35 Use This Specific Firing Order? (Engineering Deep Dive)
The 1-2-3-4-5-6 order provides even firing intervals of 120° of crankshaft rotation between ignition events. Because the VQ35 is a 60° V6, this firing order alternates between cylinder banks: 1 (right front) → 2 (left front) → 3 (right middle) → 4 (left middle) → 5 (right rear) → 6 (left rear). This alternation minimizes rocking couple and reduces vibration without requiring heavy balance shafts. The result is an engine capable of revving to 7500 RPM (HR version) with exceptional primary and secondary balance.
• Smooth idle & high-RPM stability
• No need for balance shafts
• Better exhaust scavenging
• Even-fire: 120° intervals (G35)
• Odd-fire: 90° & 150° (older V6)
• Crossplane V8: 90° intervals
Bank 1 (Right/Passenger): 1-3-5
Bank 2 (Left/Driver): 2-4-6
Front of engine = timing cover side.
🛠️ 3. How To: Verify and Use the Firing Order on Your G35
Even though the G35 uses coil-on-plug ignition (no spark plug wires), understanding the firing order is essential for:
- Diagnosing misfires: OBD2 codes P0301–P0306 correspond to cylinders 1–6. Knowing the firing order helps interpret pattern failures.
- Engine rebuilding: When installing a new engine harness or aftermarket ECU, ensure the injector and coil firing sequence matches 1-2-3-4-5-6.
- Performance tuning: Aftermarket standalone ECUs (Haltech, Link, AEM) require correct firing order configuration. The VQ35 uses a 60-2 crank trigger, but the output order must be 1-2-3-4-5-6.
- Compression/leakdown tests: Knowing the order helps identify related cylinder issues (e.g., adjacent cylinders in firing order often share head gasket stress).
1. Locate cylinder numbering on intake manifold or engine cover.
2. Use a scan tool with “cylinder contribution” test.
3. Disable injectors one by one; engine RPM drop should follow the 1-2-3-4-5-6 sequence if ignition timing is correct.
4. Check camshaft and crankshaft correlation with an oscilloscope – the ECU triggers coils according to this order.
⚠️ 4. Is It Safe? – Consequences of Wrong Firing Order
Is it safe to change or miswire the firing order? Absolutely NOT. The VQ35 engine’s mechanical design (crankshaft journal arrangement, camshaft lobe phasing) is permanently fixed to the 1-2-3-4-5-6 order. If you accidentally swap ignition coil connectors or reprogram an ECU incorrectly, the engine will experience:
- Severe misfiring and backfiring through intake/exhaust.
- Loss of power, engine shaking, and possible stalling.
- Unburned fuel entering the exhaust, overheating and destroying catalytic converters.
- Potential piston or valve damage due to improper combustion timing.
Safety verdict: Always adhere to OEM firing order. There is no performance benefit to altering it; it will only cause catastrophic failure.
📈 5. Advantages & Disadvantages of the G35 Firing Order (1-2-3-4-5-6)
✓ Perfect primary & secondary balance – no need for balance shafts.
✓ Smooth power delivery across all RPM ranges.
✓ Even exhaust pulses improve turbocharger spool (if boosted).
✓ Reduces torsional vibration on crankshaft.
✓ Enables high specific output (up to 306 hp in HR version).
✓ Excellent idle quality and low NVH.
✗ Not compatible with other V6 firing orders – no interchangeability.
✗ Requires precise cam/crank timing; any error leads to misfire.
✗ Misdiagnosis common if mechanic assumes odd-fire order.
✗ Aftermarket ECUs must be carefully configured to match order.
📊 6. Detailed Technical Specifications Table
| Parameter | Specification |
|---|---|
| Engine codes | VQ35DE (2003-2006), VQ35HR (2007-2008), also VQ35HR in later G37 but G35 specific: DE & HR |
| Firing order | 1-2-3-4-5-6 (even-fire, 120° intervals) |
| Cylinder numbering | Passenger side (right) 1-3-5 front to rear; Driver side (left) 2-4-6 front to rear |
| Crankshaft offset angle | 60° V-angle with crank pins offset 120° |
| Ignition system | Individual coil-on-plug, waste-spark not used |
| Firing interval | 120° crankshaft rotation / 240° camshaft rotation |
| Engine balance | Primary & secondary balanced without balance shafts |
🔬 7. Use Cases & Practical Applications of Firing Order Knowledge
Understanding the G35 firing order is essential for:
- Custom exhaust header design: Exhaust pulse pairing (1-2-3-4-5-6) helps equalize flow and scavenging.
- Standalone engine management: When swapping a VQ35 into another chassis, configure the ECU ignition output to 1-2-3-4-5-6.
- Performance camshaft installation: Degreeing cams requires knowledge of firing order for proper valve timing events.
- Vibration analysis: If you feel an odd vibration at specific RPMs, checking firing order integrity via oscilloscope can reveal misfiring cylinders.
- Engine synchronization after timing chain replacement: The timing marks on cam sprockets are set relative to cylinder #1 firing TDC.
🧪 8. How to Troubleshoot Firing Order Related Problems
Symptoms that may indicate firing order issues (despite modern ECU control, wiring mistakes happen):
- Rough idle + P0300 random misfire: Could be crossed coil connectors if someone swapped harness plugs.
- Backfire on deceleration: Indicates ignition event at wrong time.
- Engine cranks but won’t start: In extreme cases, reversed firing order (e.g., 180° out) can prevent starting.
Diagnostic tools: OBD2 scanner with live data, ignition timing light (check that cylinder #1 fires at correct timing), lab scope for crank/cam correlation.
❓ 9. Frequently Asked Questions (Expert FAQ)
What is the exact firing order for Infiniti G35 VQ35DE?
1-2-3-4-5-6. Cylinder #1 is passenger side front, #2 driver side front, #3 passenger middle, #4 driver middle, #5 passenger rear, #6 driver rear.
Why didn’t Nissan use 1-6-5-4-3-2 like some V6 engines?
Nissan engineered the VQ series with a 60° bank angle and specific crankshaft offset to allow the sequential 1-2-3-4-5-6 order, which reduces vibration and improves throttle response.
Can I change the firing order with a custom camshaft?
No. The crankshaft journal phasing is fixed. Changing cam lobe order would require a custom crank, which is not practical.
Does the G35 firing order affect the exhaust note?
Yes. The even firing sequence produces a smooth, linear V6 growl. An uneven order would cause a lumpy idle similar to a crossplane V8.
What happens if I swap two ignition coils on a G35?
Swapping coils between cylinders will alter the effective firing order, causing severe misfire, backfire, and possible catalytic converter damage.
How do I confirm my G35 has correct firing order?
Use a scan tool to monitor misfire counters. All cylinders should have low counts. Perform a cylinder balance test; RPM drop should be equal across cylinders.
Is the firing order same for manual and automatic transmission G35?
Yes, transmission type does not affect firing order. All G35s with VQ35DE or VQ35HR share the same order.
Can a bad crankshaft position sensor cause firing order confusion?
The ECU relies on the CKP sensor to determine firing order timing. A faulty sensor can cause incorrect ignition timing but not change the order sequence.
What is the difference between firing order and cylinder numbering?
Cylinder numbering is the physical labeling; firing order is the sequence in which they ignite. For G35: numbering = 1,2,3,4,5,6 physical; order = 1-2-3-4-5-6.
