I've had an audible tap in the engine for some time. At first, I was afraid it was a rod knock, but it comes and goes with no apparent reason. Recently, I noticed a difference in the initial 'tip off" when I accelerate from stop. When there's no tap, the car really "jumps", and when it's tapping the response is flatter. Wondering if this could be the VVT solenoid. Any one have a similar experience with this? I would also add that the valve seals are bad, but I can't see how that could be connected.

Thanks,

 

With the engine running place you hand on the VVT and rev the engine a little. If it is the VVT chattering you will feel it. If it is then first change the oil and filter and see if it goes away.

 

Do Gus's suggestion first. If that is not it was the engine overheated. Tapping sound could be dropped valve seats. The best way to check is with compression test.

 

Thanks all for the helpful suggestions. I'm going to try Gus's idea first which will hopefully pan out. I've had the car for about 10,000 miles and its always run very smoothly. Even with the noise (sounds more like a steady tap rather than a "chatter"), which seems to come and go, and seems to correlate directly with engine rpm, I can't say that I have any complaints (except for the bad valve seals, which could been affected if the engine had been overheated by the previous owner).

All of the timing chains have been replaced since I've owned the car, as well as the other usual suspects (water pump, thermostat housing, etc.). If I can't manage to find the source of the tap, I'll just have to turn up the radio a bit louder and hope for the best.