A couple of months ago, I noticed a strange tapping noise coming from my engine. It's not like anything I've heard before, and it only does it when the engine's cold. After driving a couple of miles, it goes away.

The noise has a slight metallic sound, but is "soft" on either side of the ping. It's a regular noise that speeds up and slows down with the RPM's. It has characteristics like it's an exhaust leak, so that's the first thing I checked out. No leak. I bought a mechanic's stethiscope (sp?) and checked out the valve covers thinking it might be a slightly loose rocker arm. No go. I put Techron in the gas thinking it might be a slightly sticking valve, but it hasn't done any good. I then put Marvel Mystery Oil in the oil thinking it might be a colapsing lifter. No good.

So yesterday I took off the injector covers, and felt some of the injectors. And I can definitely feel them tap as they open and shut, and as far as I can tell, the tapping coincides with the noise.

I'm going to try two more things, but I'd still like your opinion. I'm going to get the stethiscope and see if it's definitely coming from the injectors, and I'm going to try it when the engine is cold and the noise is happening, and when the engine is hot and it's not.

Any suggestions would be appreciated. Especially if this is a known problem.

Assuming it is the injectors, are they expensive, and are they hard to replace?

Cheers!
W

 

You have described exactly what mine does when it's cold. I always assumed it was a minor exhaust leak, and was normal, as it stops when it gets warm.

I will have to check my injectors also. The noise is metallic in nature, but soft or muffled, and always quits after it warms up a little. I figured whatever it is, it's minor.

 

It could be valve lifter noise.

 

It 'could' be that stupid AIR PUMP.

Mine makes a sound like a rod knocking until it warms up.
Don't you just hate to replace a part that you don't want much in the first place?

You can try a quart of transmission fluid in the oil to see if it will quiten down a noisy lifter. If it's a lifter.
Run it until the next oil change and then go back to your regular oil.

But listen around that air pump first and see it that is causing the noise.

Good luck with it.

 

for about $5, go buy one of those stethoscope things. It looks like the one your Dr. uses, but it has a long aluminum pole which you can place on the motor to try to find the general location of the tapping noise. You can get a Pep boys, Harbor Freight, or just about any auto parts store.

P.S. You do not need to have a medical degree to use this gizmo!!