kau

I have a 2003 Honda Accord with less than 50k miles. 4 cylinder.

At idle the whole car shakes. Turning off the AC/Heat does not change it.

No check engine light. Changed the O2 sensors recently and no help. Oil changed often.

Any ideas?

f22b1 coupe

Occasionally spark plugs can be worn enough to cause the car to shake but that's unlikely. I would pull one and check the gap, make sure they aren't worn prematurely.

One of the motor mounts could already be broken on it, sadly that is something that plagues almost all of the older Hondas I've encountered, although for one so new it seems unlikely. It could be something being weak though- weak spark from worn plus, weak coil in one of the cylinders, weak spray from a clogged fuel injector- something like that.

It's not an all out misfire or the CEL would definitely be on. I can't remember if they started using MAF sensors on the air intake on Accords in 2003 or not. Do you know if your car has a MAF sensor?

THis would certainly be extreme, but a timing chain only develops enough slack to create bad ignition timing if the chain, guide/tensioner, or sprockets develop play. And the main condition that this happens under is oil starvation/neglect. Again, at that mileage it seems like such a slim chance.

If it were my car, I can tell you what I would do. I would replace the spark plugs, dump a bottle of fuel injector cleaner in it, and if that didn't fix it, I'd suck it up and get a $75 MAF sensor from a parts store.

f22b1 coupe

Oh and there is an idle control sensor/unit listed for that on Advance's website, so I suppose you could try that first, it looks like there are two separate units listed for that, and they aren't cheap either. Again, if this were my car, I'd be doing plugs and fuel injector cleaner first, then I'd probably get ahold of a used set of those idle controls. Then last I would try the MAF if nothing else seemed to fix it. I know throwing parts at it is kinda shitty, but it beats paying a shop even more for just one thing.