99 tahoe tapping noise -egr?

on this tahoe sometimes not always usally when it is cold for at least a hour it will make a tapping noise witch seems is coming from the front right of the engine but yet it dosn't compoletly sound like lifter\valve valve noise , maybe more towards exhaust noise , could it be the egr sticking? if so shouldn't it set a lean condition code? it dosn't have any codes now

the egr doesnt open at idle, and ive never heard of one making noise. my guess is you have a lifter that is unloading.the noise will go away after the lifter loads back up.

an egr thats open at idle will cause very rough running/hard starting.

Hi, I'm new to the forum. I just read your problem. I saw a report on the internet or someplace that some GM engines developed a piston slap due to excess wear to one of the pistons, don't remember which one. It sounds like a knocking/tapping noise almost a diesel like sound that gets louder over time. It is most noticable when the engine is cold and quiets down after the engines warmers and the oil gets flowing.
This may or may not be the problem, but something to at least check out. Hope this helps.

Roy

I had the same problem with my '98 Tahoe. I narrowed it down to a couple of valves slapping on the passenger side of the engine. I pulled the valve covers, and remove the extremely loose rockers and pushrods. I checked the rods for straightness. All seemed to be ok. So I went ahead and reset all of the valves by tightening down each rocker as the manual suggested. I found manual suggestions set them far too tight, in which case I backed the nut off about 3/4 of a turn on each. Needless to say, the problem still existed. Knowing the lifters are hydraulic, I figured that some of them may be clogging up??? Don't know for sure, but went ahead with the next step. Put some "Gunk" engine flush through a few 5 min. cycles at idle. Drained the oil, then replaced the oil and filter. The engine runs much smoother and there isn't any tapping at all, even when cold startup. I'm not sure if I fixed the problem, but the vehicle definitely runs much better.

How does one determine if he has damage to the piston or not without removing the heads and all the junk ? I too have the ticking but it sounds more exhaust than anything. I shall try the engine flush of the lubrication system , if that works then so be it , If not..You'll be hearing from me again >_<