Question: I have a 2002 Isuzu Rodeo with a 3.2-liter engine and 103,000 miles. About 2000 miles back, I replaced the timing belt, water pump, and the hydraulic tensioner. Since then, it has been difficult to start at times, whether the engine is hot or cold. Sometimes when cranking the engine the starter has a dead spot, but if you push down on the accelerator when starting it, the starter releases and it starts. Other times, it starts without any trouble. Again, there were no problems starting the truck prior to replacing the timing belt. I have connected a scan tool to it to check for any DTCs, but it doesn't show any.
Answer: The timing belt connects the crankshaft and camshafts, keeping them in time -- meaning the intake and exhaust valves will always be in the correct position in relation to the pistons traveling up and down in the cylinder bores. It is possible (and it has happened before) that the technician who replaced the belt was off a tooth. The crankshaft and camshaft pulleys are marked, and both must be rotated to the correct position where the sprockets' timing marks line up exactly with the corresponding marks on the engine and cylinder heads. Then the timing belt can be installed, and the camshafts will be in time with the crankshaft. But nobody's perfect, and a sprocket may have inadvertently moved or been misaligned prior to the belt going on. Therefore valve timing is now off a tooth and incorrect. Once in a while, the engine may still run well enough for this type of condition to go unnoticed. Symptoms may include a hard start -- difficult engine rotation by the starter due to compression being unbalanced. But timing being a tooth off would typically produce additional symptoms such as rough running, vibration, and a lack of power. I hesitate to condemn the timing belt installation right off the bat. It may be a coincidental onset of a starter problem, possibly a weak battery, defective starter, or poor connections between the two. Have the technicians fully test the battery, charging system, and starter operation. If all looks good, it should only require partial disassembly to confirm that the timing belt is in or out of time.
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