I've got a '94 truck with 22re engine and 152K miles. Engine generally runs good and smooth, no smoking. But when I'm driving there is a knocking/tapping noise coming from the enigne with only very light throttle application. When your accelerating its fine and with your foot off the accelerator/coasting its fine, you only hear it when you give a light throttle input. Any thoughts would be great! Thanks in advance!

 

sounds like valves might be out of whack.

 

This same thing happen to me, I forgot to put the fuel filter back on after a put a new one in, it would hit the inner frame with a very loud knocking noise. It would only do it when I gave it gas (idle was fine). Check to see if any fittings are loose first before you start looking into big problems.

Thanks,
Mario

 

is it a tick or a knock?

 

It's more of a knock than a tap. I'm afraid it might be a rod bearing, but I hoped someone might have seen something similar. I'm also wondering if any type of timing chain problem could cause this noise.

 

If it is around the 2K rpm range then I would say timming chain. But that sounds more like a rattle, like running a stick along a chain link fence type sound.

 

I had a rod knock that gave the same symptoms. It could only be heard at very light throttle at first, and it sounded more like a wrist pin than a rod knock. If you can get it to make the noise without driving it, have someone run the throttle while you crawl underneath it. If it's a rod knock it'll be way way louder when your head is close to the oil pan.