After a couple of sub zero temp days last weekend, I was blessed Tuesday this week with a new noise coming from the drive train area. The only pattern I can come up with is that it's a tapping sound that appears only when accelerating and mostly between 30 and 50 mph. I goes away if I get off the pedal and it usually goes away if I steady out a cruising speed, but not always. The tapping gets louder and speeds up if I accelerate faster and is slow and more faint if I'm accelerating slower. I can't nail down if there's a specific gear it seems to happen in.

No warning lights. Recent oil change. No leaks. Car shifts smooth. No loose items in the engine bay. The sound is similar to tapping a wrench against the side of the engine.

Known issues and active paranoia:
Missing a wheel stud on front right. Brakes installed in June seem warped. There is an exhaust smell at startup and when sitting at stops that gets pulled in buy the heat/air conditioning if it's on. No visible exhaust leak.

I don't want to, but I'm on the edge of trading this thing in with all of these little things that keep coming up.

 

Sounds like your spark plug has come loose again.

 

Sounds like rod knock. I hope I'm wrong on that for your sake.

BTW, these...

"Missing a wheel stud on front right. Brakes installed in June seem warped."

...are related. Without equal torque on the rotor, they will warp. It's also dangerous to be driving around with a missing stud. You can get away with it a little better with 5-bolt hubs, but on a 4 bolt, it's unsafe.

 

I'm hoping that the sound only happening when in drive means it's not a rod or bearing. As far as the wheel stud, I started getting quotes for the replacement. This has happened before once or twice, so I may have a set of ARPs installed this time.

There was a post last week by GeePondy about a Wheezing/Whining sound that I just found that happens under the same circumstances as my tapping sound. I don't get it. I'm going to check the plugs tonight. The part about the sound only occurring while driving and not while in park or neutral also has me confused.

The part about only happening while driving and between 30 and 50 had me thinking transmission? Any other processes happening at that speed/rpm and while driving?

 

Ah. I see. If it were rod knock, it would happen at idle and anytime the motor is revved, whether or not under load.

So, the sound only happens when the car is moving and under load? You say it tracks with acceleration.
Does the sound track the revs of the motor/trans or the speed of the car irrespective of revs?

 

I'm still voting loose spark plug

The exhaust smell at idle and a ticking noise are consistent with a leaking plug. If the threads are bad, it might make the noise even if tight.

 

Sneefy it does track the rpm of the car. I didn’t drive as much today as I usually do for work, so it was a while before it kicked in. I’m starting to notice that it only happens once the engine is good and warm. Again, nothing when in park. So after I check the plugs, if it happens again, what about it maybe being the water pump or timing belt starting to struggle? Could that be why there’s a noise only under load but not idle/revved while in park?

 

check my other post since you seem to be posting the same question in different threads. Also consider since it is wintertime, that snow/ice/debris could be lodged in the wheel or brake caliper since it is speed dependent.

 

Thanks, Burnt. I checked that post. I ran the car through a good car wash to see if any winter road crap was playing a part. We have a warm spell and I'm in my car all day, so I'll just keep looking for patterns. I have work that has to be done to pass inspection in about 60 days, so maybe I'll stumble on what it is.

I've had an oil pump go out on an Odyssey and it was a much harder tapping sound, but I don't have an oil pressure light on like I did with that. I still wonder if anyone has experienced a failing water pump and if it sounds similar.