Ok prior to this i've did searching all over the site. I've been under and around the car looking for exhaust leaks...none to be found. Its only in the two rear cylinders on the drivers side(used stethoscope). I've pulled the rockers and pushrods twice. Everything looks good. As long as i baby it <3krpms its not there. only if i try to run it out and it gets hot. The other morning it did it on start up which was real weird. Only occurs normally when hot. No SES light. Oil pressure is good. Any good ideas? Didn't do any lifter replacement. Like i said though, its when its HOT or after running it out. No oil pressure problems, i use mobil 5/30, tried 10/30 no difference. I swear its pulling timing even though i can't prove it.

 

Ive heard of two common things. First being a possible burnt valve letting more or less through then it should. The second is more common with newer engines, especially the V6. Watched a deal on what they called a sort of piston walk. The rod allows the piston to move very slightly left and right causing a terrible knock. Might consider taking off the oil pan and watching the piston travel while slowly turning the crank and check the surface around the cyclinder wall on the under side of the block. Either way GL...

 

Thanks for the info. It really does sound as though it would be coming from the bottom end, but its only when its hot which stumps me. I would think any kind of piston walk would be when cold while tolerances were greater. Definetely not ruling it out cause untill its solved its an idea. Anyone else ever hear of Steam cleaning the engine? I heard of guys doing it on LT1 engines but never tried it on my ls1. Supposedly it steams the valves. Throttle it up and try and spray some water through it?

 

Those kind of noises are hard to find but the best bet is to try to narrow it down before tearing it down. Noises when it's hot or after a hard run generally imply lower oil pressure or parts expanding. Take your time - I once found carbon build up problem by removing the plug and starting it up - keep checking, you'll figure it out.

 

I have heard of steam cleaning combustion chambers of carburated engines. But, I would not consider doing it on a fuel injected engine. On a carb engine the water is sparingly put through the carburator butterfly while the engine is hot and running. The thermal shock blasted carbon deposits. How would you introduce the water on a port injected engine?, while running?, and do you know what this would do to any modern engine's sensors? Also, the LS1 is not a low compression engine. If you get too much water in any one cylinder, you could break a rod--water does not compress. I would not recommend doing it. I would first try a combustion chamber cleaner that goes through the fuel system.

From your description, it sounds like it could be pre-ignition or detonation. Either of those could cause the computer to pull your timing--but so could a mechanically induced knock. Have you changed your plugs lately? If so, you may have a burr hanging in the combustion path--the burr would cause a hot spot that could cause pre-ignition, so can a plug that is damaged or is too hot of a heat range, so can excessive carbon deposits.

If you have the time, you may be able to help diagnose the problem by sending a sample of your oil to a lab for spectrometric analysis. This test will tell you if you have abnormal amounts of metallic particles. The type of materials (bronze, aluminum, iron, etc.) noted can lead you in your diagnosis. Sample kits are available on-line and in some auto parts stores.

Unfortunately, there can be a number of causes. Keep us posted on any additional information.

 

Can anyone recommend a good internal engine cleaner? I'll try throwing some fuel system cleaner through it, but should an oil passage or something be gooped up? Since i'm running synthetic i'm not sure how compatible other oil additives are. I'll work on pulling plugs, only have 46k, but atleast to look see if those cyclinders look odd. Thanks all for the thoughts.

 

seafoam...this is a guide for a LT1 but will give you the general idea

http://www.**************.com/camaro...m/seafoam.html

 

my 99 corvette makes a ticking sound also, when it idles or comes down from rev up, only low rpms, so i had my machanic look at it, is said its a fuel injector, says he thnks it needs to be cleaned out, not to sure tho

 

AFter reading through my gm repair manual they list a possible cause as being a missaligned valve spring...not sure how thats possible but i figured i'd give it a whirl. Pulled the rockers loose and turned the spring a bit, and somehow or another i have yet to hear that noise again. I wound it out hard on the highway and everything. Really weird but for now that seems to be the solution to my problem till it comes back, thanks to all

 

how hard is it to take the intake off to get to the springs?

and the oil pan?

any guides online?

i have a problem similar to chris_camaro: "makes a ticking sound also, when it idles or comes down from rev up, only low rpms"

i also got under the car while it was running and it seems louder on the bottom end.

 

take out the several (5)maybe, bolts that hold the coil packs onto the valve cover. Then loosen the 4 bolts that hold the valve cover onto the head which are underneath the coil packs. They say to replace the valve cover gasket when you pull it but i didn't and i don't have any leaks. theres a bolt going through the rocker arm, just loosen it to relieve pressure off of the valvespring and give it a 1/4 turn. Can't explain how or really why it worked but its in the factory gm manual as a possible cause and for me it was the problem. I think the rocker arm torque is 22?ftlbs, and the rest of the valve cover holddown bolts and coil pack bolts are minimal, 10 seems to ring a bell but don't hold me too it.

 

where can i purchase a gm repair manual for a 2000 trans am? dealer?

 

Helm sells manuals that are the same as the factory manuals. Might want to check ebay. I bought a factory set for my 98 for 35 bucks in excellent condition.