2000 Isuzu Rodeo 3.2L V6 DOHC P0300 Code: Rough Idle, Coil Pack Issue & Timing Belt Installation Fix
I recently replaced the cylinder heads on my 2000 Isuzu Rodeo due to camshaft locking issues. After head replacement, I performed a timing belt and spark plug replacement as routine maintenance. Upon reassembly, the engine exhibits a very rough idle and has triggered Diagnostic Trouble Code (DTC) P0300 — indicating a random misfire. When testing the coil packs for firing, I found that the spark plugs on the driver's side are not firing at all. I was advised that the #6 coil pack is specifically designed for cylinder 6 and must be installed in the correct position. However, despite proper installation of the coil pack, the misfire persists. The engine runs unevenly, especially at idle, and the P0300 code remains active. Could this issue stem from improper timing belt installation? I've read that many DIYers incorrectly install the timing belt on 1998+ Isuzu 3.2L V6 engines — simply aligning marks is not sufficient. The correct procedure involves precise alignment of cam and crankshaft marks, with specific attention to the driver's side cam. Key points: - The timing belt should have three visible marks: two solid lines for the cams and one dotted line for the crank. - Align the crankshaft mark on the timing belt sprocket with the oil pump mark — these are clearly marked and easy to identify. - For the passenger-side cam, rotate it until it 'springs' into position. Line up the cam sprocket mark with the cylinder head marking at 12 o'clock (relative to the valve cover). - The driver's side cam has two marks: one at 12 o'clock and one at 9 o'clock. It must be aligned to the **9 o'clock** position, not 12 o'clock. - After aligning both cams, install the timing belt with the dotted line matching the crank sprocket mark (use a shop rag between the belt and oil pump for stability). - Use a box-end wrench (not a ratchet) to turn the driver's side cam to the 12 o'clock position and hold it in place. - Secure the timing belt with clips, ensuring all components remain aligned. - Finally, remove the hydraulic tensioner pin and verify alignment. For added safety, temporarily install the lower crank pulley and start the engine briefly to confirm proper operation. Additionally, I’ve learned that while all coil packs are mechanically identical on 2000+ Isuzu Rides, the #6 coil has a shorter boot and sits lower on the valve cover than others. This physical difference may be overlooked during installation — it's important to visually inspect this detail when replacing coils. Any confirmation or additional insights on P0300 causes related to timing belt misalignment or coil positioning would be greatly appreciated.
This is an older thread, but it lacks a definitive answer — so I'm providing a clear explanation for future searchers. The most likely cause of the P0300 code and rough idle in your 2000 Isuzu Rodeo 3.2L V6 DOHC engine is improper timing belt installation. Many incorrect guides exist online that only suggest aligning marks, which is insufficient for this engine. For proper installation on 1998+ Isuzu 3.2L engines: - The timing belt should have three visible marks: two solid lines (for cams) and one dotted line (for crank). - Align the crankshaft mark on the timing belt sprocket with the oil pump mark — these are clearly defined and easy to spot. - Begin with the passenger-side cam. As you turn it, you'll notice it 'springs' into specific positions. Find the cam sprocket mark and align it with the cylinder head marking at 12 o'clock (relative to the valve cover sealing surface, which is aligned at 9 and 3 o'clock). - Rotate the passenger-side cam until the cam mark lines up with the head mark — this may take several turns. - For the driver's side cam, there are two marks: one at 12 o'clock and one at 9 o'clock. It must be aligned to the **9 o'clock** position, not 12 o'clock. Once both cams are properly positioned: - Prepare the timing belt with clips for support. - Start installation by aligning the crankshaft dotted line with the sprocket mark (use a shop rag between the belt and oil pump to prevent slippage). - Align the passenger-side cam line with its marking. - Use a box-end wrench (not a ratchet) to turn the driver's side cam to the 12 o'clock position, holding it firmly in place. - Carefully install the timing belt so that the dotted line aligns with the crank sprocket mark and the pulley marking. - Secure the belt with clips at appropriate points. Double-check all components to ensure nothing has shifted. - Remove the hydraulic tensioner pin and verify alignment. If done correctly, the engine should run smoothly. As a safety step, I recommend temporarily installing the lower crank pulley and running the engine for a few seconds to confirm proper operation. Note: The #6 coil pack on 2000+ Isuzu Rodeos is mechanically identical to others but has a shorter boot and sits lower on the valve cover. This detail should be carefully inspected during installation — it's easy to miss, especially when replacing coils.