Quick answer: Spark Plug Replacement on a 2004–2007 Cadillac CTS is rated Moderate and takes about 2-3 hours. You'll need 9 tools for this job, and parts cost about $50. This guide walks you through the full job step by step, including the mistakes to avoid.
| Part Name |
Part Number |
Price |
Buy |
| Spark Plugs |
— |
$50.00 |
|
About prices: shown prices are typical retail averages and change frequently; cheaper alternatives may be available. Confirm the current price before buying.
💡 Pro tip: Order all parts at once to save on shipping
Step-by-Step Instructions
Follow these steps carefully
1
Cool the engine (verify 2004+ LY7!)
The 2004–2007 Cadillac CTS 3.6L (LY7 V6) uses ACDelco 41-990 double platinum plugs. Gap: 0.043". Torque: 15 ft-lbs. Note: the title may say '2003–2007,' but the 2003 CTS had the 3.2L (not the 3.6L LY7). The 3.6L LY7 is 2004–2007 ONLY. If you have a 2003 3.2L, this guide doesn't apply. Catalog confusion: 41-990 vs 41-988 — verify the 41-990 is correct for your LY7 (the 41-988 is a different application). You'll need: 6x ACDelco 41-990, spark plug socket, extensions. Critical: let the LY7 cool — aluminum heads. The LY7 is port-injected (not DI) — the plugs last well.
🔧 Mechanic's note — Tom Becker
I verify the LY7 and let the CTS cool — torque wrench out for the plugs, always. The 3.6L aluminum head does not forgive, and I have done the timesert repair that proves it. I would rather spend the extra two minutes.
2
Access the ignition coils
Remove the engine cover. The LY7's layout is straightforward — no plenum removal needed for basic access (unlike the later DI 3.6Ls). Unplug any connectors blocking access. The port-injected LY7 is simpler than the later direct-injected versions.
3
Remove one coil at a time
Unplug the connector, unbolt the coil, pull it straight out. The 2004-2007 CTS is getting old — the boots may be brittle. Replace any damaged boots. Don't mix up the coils.
4
Remove the old spark plug
Remove the old ACDelco 41-990 with your socket. The old double platinums should show normal LY7 wear. If a plug is oil-fouled, the valve-cover gaskets are likely leaking (common on the aging LY7). Don't drop anything into the wells. Verify the old plug is the 41-990 (not the 41-988).
5
Gap and hand-thread the new plug
The new ACDelco 41-990 double platinum comes gapped at 0.043" — verify (double platinum can be carefully adjusted if needed). Hand-thread the new plug into the LY7's head until it seats. NEVER wrench-start — the aluminum heads strip. The LY7's plug wells are accessible — hand-threading is easy. If it binds, back out. Ensure it's the 41-990 (verify against the 41-988 confusion).
🔧 Mechanic's note — Tom Becker
I gap and hand-thread the CTS plug — then one hand on the ratchet to tighten. I have stripped plug threads with two hands on the wrench, and I have learned my elbow lies about snug.
6
Torque to 15 ft-lbs
Torque to 15 ft-lbs. Use a torque wrench. Do not over-torque — the aluminum heads strip. The accessible layout means precise torquing is easy. The 15 ft-lbs ensures good seal for the port-injected combustion.
7
Reinstall the coil
Reinstall the coil — seat it firmly, bolt it down, reconnect the connector (click). Repeat for all 6, one at a time. Reinstall the engine cover. Verify all connectors are clicked.
🔧 Mechanic's note — Ray Delgado
I reinstall the CTS coil and I seat the connector until it clicks — the LY7 coils are buried, and I am not going back in. I have learned that the click is the only confirmation I trust down in that valley.
8
Reassemble and test
Start the engine — the 3.6L LY7 should idle smoothly with its V6 burble. Check for misfire codes. The 2004-2007 CTS's LY7 is port-injected and robust — the plug job is simple. Test drive: the LY7 should pull cleanly. The ACDelco 41-990 at 0.043" and 15 ft-lbs is the correct setup. Remember: this is the 2004–2007 LY7 — if you have a 2003 3.2L, the plugs differ. The 41-990 vs 41-988 catalog confusion means you should verify the part number on the old plug. The double platinums last ~100k miles.
All Done!
Test your repair before closing everything up. If something doesn't work right, double-check your steps.
⚠️ Common Mistakes to Avoid
- • Not properly gapping the new spark plugs
- • Failing to torque the spark plugs to manufacturer specifications
- • Not replacing the intake manifold gasket when removing the manifold
