94 YJ with 6cyl auto with 82k on it. The motor is tight as a drum and runs flawlessly. However in the last 2-300 miles it has a slight little tapping noise at idle. the previous owner rarely drove it and I was wondering if the valves ever need adjusting on a YJ or if it is something much more serious. The previous owner said that he had the motor blueprinted (why on earth I don't know). And he may have fed me a line of BS too. Not out of the question. If every used vehicle ran like the owner says it does, mechanics would be out of business!! All in all the Jeep is great, but I am concerned about the noise. I have checked the fluids and all, but not changed them. Just bought the Jeep and have put around 700 miles on it in the past 2 weeks. I am going to change the oil and filters tomorrow and see if that helps. Any info is appreciated.

I too have a '94 YJ SE 4.0. It has a tap that sounds like a valve tap since day one. I remember back in the usenet days, there were many discussions about this in the jeep groups. I've learned to ignore this tap, and I have 112,000+ miles on mine and still running strong. If your power and mileage are strong, your fluids look good, and the engine revs smoothly, learn to live with this.

I've noticed over the years that I often hear "new" noises while driving. Often these noises are not present or noticeable the next time I'm at the wheel. My advice, turn up the music.

A Jeep mechanic recently told me that the 6 cyl 4.0 is notorious for exhaust manifold gasket failures at the rear of the manifold. When the gasket fails the exhaust leak makes a noise that is identical to a valve tap. Sounds like a very common problem with that engine. I would check that. I am like you - i hate engine noises - taps, rattles, etc. drive me nuts. Chasing one down right now.

I have sort of learned to ignore it by turning up the radio. I have also heard about the exhaust issue on these jeeps and I am going to get that checked out next week. As of now, just gonna drive it and have fun in it. Thanks for the replies.

I never heard about the exhaust gasket problem before, but I won't nay say it either. Mine taps like diesel, and always did, and there's no exhaust manifold leakage. I did have a hell of a rattle from the cat. Replaced that and the cat back, and it's all good.

I just had my cat and muffler replaaced yesterday and boy, it sounds like a whole different vehicle now, except now I can hear that exhaust leak coming from my manifold.
Time to get out there and fix that now ith the old german torque specs,, gudentite