I have a Honda Civic 2001 LX with automatic transmission and 56,000 miles that has received regular service. When I am driving between 35-45 mph, usually accelerating slightly over a fairly rough road with cracks and potholes or uphill, it sometimes shudders or stutters for a second or two. I am not using the brakes at all. If feels like something is catching and releasing. I can feel it through the steering wheel and floorboards. It doesn’t seem to happen necessarily when the gears are shifting. Unfortunately, the mechanics haven’t been able to reproduce the problem, though any passengers in my car could verify it, so I’m not imagining it.
Over the last year, I have had it checked out three times by two different trustworthy auto repair places to identify the problem, but wiht no luck. I’m concerned that if something is catching, it could be wearing away or will break.
Any ideas?
sounds like one of your cylinders is missing. That’s usually either a bad spark plug or a bad injector. Spark plugs are cheap and should be replaced from time to time anyway. I’d start there. Wouldn’t hurt to do the wires as well (be sure you get 'em back on in the right order 
)
If that doesn’t cure it then it’s time to test the injectors.
Same thing could happen if a plug wire were damaged (inside the insulation).
Perhaps alternately connecting and disconnecting with the vibrations.
This is vaduma (with login problems).
Thanks for your responses and possible diagnoses. I’ve had a missing cylinder because of a bad spark plug, and this shudder (rata-tata-tata-tata)just doesn’t feel or sound like that. It sounds like something is very briefly caught and it feels very bumpy. My bad spark plug problem felt more as if the engine gasped and briefly lost power.
I will mention both of your suggestions to my mechanic, of course–and I do appreciate your replies. And does anyone else have any ideas?
Wouldn’t hurt to check engine mounts.
[b]The problem might be in the torque converter clutch.
When the vehicle reaches a certain speed, a clutch in the transmission torque converter is supposed to engage. This allows for better fuel economy. Sometimes for some reason this clutch fails to engage fully. And this can result in what is called clutch shutter.
The first thing to try is have the transmission fluid exchanged if it has never been done. This will sometimes eliminate clutch shutter. If this doesn’t work, a product called LubeGard has come out with an additive for the transmission fluid called Shutter Stop that eliminates clutch shutter.
Tester[/b]
vaduma here again. I took it to a respected local repair service. The mechanic was with me to hear the rumble-strip-like sound occur a couple of times, but he wasn’t able to come up with a definite solution. He changed the transmission fluid to the standard Honda fluid and sent me to the dealer.I’d given them the results of this discussion forum. The dealer wasn’t able to reproduce the sound, but changed the air filter. No codes are showing, no engine light. It seems to baffle everyone.
Thanks for your help.