2012 Honda Odyssey - Doing the timing belt, should I add plugs to that?

I am having the timing belt replaced as to maintenance specs. Should I replace sparkplugs too?

It depends on your vehicles mileage. sparkplugs now a days last about 100k. but I would replace the water pump.


Yeah, you’re probably at somewhere between 100,000 to 105k miles, right? Time for plugs as well. @weekend-warrior is right. Do the water pump. Also do the tensioner and the pulleys. You want the full timing kit. Many Honda dealers will only replace the pulleys/pump/tensioner if they’re already bad, but you want them to replace them regardless. It’s going to suck if one of them dies in 50,000 miles and you have to pay for the whole job over again, and it’ll really suck if whatever goes out takes the timing belt with it and wrecks the engine.


I think 100K is too long between spark plug replacements. The manufacturer has a bias to spec long replacement intervals b/c it improves the “cost to own” spec that many buyers use to decide which new car to buy. If you haven’t replaced the plugs within the last 50 K miles, suggest to replace them and continue on that interval or less. Proactively replacing the water pump/pulleys/tensioner along w/the timing belt as mentioned above, and replacing the coolant, that all probably makes sense also. If you are low on funds the priority is 1) timing belt, 2) water pump, 3) spark plugs. The spark plugs can be replaced independent of the other two without much cost penalty. The downside of waiting too long on the spark plugs is if you wait too long you might start getting misfires and ruin the cat, which is an expensive part to replace.

CV9999G00017A.pdf (honda.com)
sorry but Honda says 105k. 50k is a little extreme

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$275 p&l for spark plug replacement, $2000 for a new cat. Replacing the plugs a little early seems like good insurance.

This vehicle has a maintenance computer, timing belt and spark plug replacement occur at the same time, maintenance code B4.

If the expense of replacing the spark plugs at this time is an issue, it can be deferred for a year or two, these are iridium spark plugs they will last a very long time.

I replace spark plug as part of the 120,000 mile service, performed one on Wednesday, never an issue. Misfires are usually caused by coil failures. Last year I replaced the spark plugs on a 2008 vehicle with 250,000 miles, I told the service writer that new spark plugs would not fix the check engine light, the owner wanted them replaced in addition to the repair because they were the original spark plugs.


Don’t forget the transmission fluid. With all that’s mentioned above, this could easily turn into a $2000 maintenance job. When I did the timing belt on my 2005 Accord V6, I asked about the pulleys, tensioner, and oil seals. The dealer said they don’t usually do them, would inspect them, and call me if they needed attention. No calls and no problems after an additional 80,000 miles when I sold it. The trans fluid can wait for you next oil change, but should be changed at least as often as every 60,000 miles IMO.

If your Honda engine is like mine, the valves should be checked and probably adjusted. It makes sense to do this when changing plugs or timing belt.

Another option when deciding whether to change plugs or not, at 50- 80% of the recommended change interval, ask the shop to remove a couple for inspection. If the electrodes still look ok, gap is still in spec, reinstall and defer the replacement expense until later.

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Please let us know about all the failed cats caused by changing plugs according to the owners manual. I can’t think of one.

What I WOULD do is change the transmission fluid at least every 50k with Honda fluid.


Yes on the plugs

In addition . . .

You do every single thing under that timing cover

Timing belt
complete tensioner assembly, every single part of it
idler pulley
all the cam- seals
crank- seal
looks like the water pump is also driven by the timing belt . . . do it, as well

skip any of these at your peril

You want everything under the cover to be good to go . . . and the only way to be sure is to replace it . . . until the next timing belt job

I’m assuming you’re planning on keeping the van for a few more years, correct?

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Here’s what an owner of an independent auto repair shop suggests :

"spark plugs must be replaced when they wear out. The best guide is the manufacturer’s mileage recommendation, though these are sometimes at the extreme end of service. Not replacing spark plugs in time can result in damaging ignition coils and other components…

A misfiring spark plug is extremely damaging to an engine. When the spark plug fails to fire, the fuel in the cylinder is not burned. This unburned fuel enters the [catalytic converter], where it drastically increases the temperature. One misfiring spark plug can destroy an expensive catalytic converter in a matter of minutes…

Best is to have spark plugs inspected, when mileage approaches the recommended interval. Eighty-percent is a rule of thumb recommendation for inspection and sooner if a problem is suspected. For instance if the recommended replacement interval is 100,000 miles, one or two plugs might be removed for inspection around 80,000 miles."

Still waiting for any actual, you know, evidence, proof, facts. A repair shop recommending more frequent than specified services doesn’t qualify.

Iridium spark plugs don’t wear out, following the maintenance schedule seems reasonable, not twice as often.

The spark plug on the left was replaced at 120,000 miles, the one on the right, 40,000 miles.
The difference in maintenance schedules is because the one on the right is from a turbocharged engine, more deposits on the plug.

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