So, I purchased my 99 3.8 camaro back in early July. Being that it is used, i was expecting some problems. Just replaced the clutch, had to do so because i thought i had a rear main leak, turns out it was the entire structure housing. Luckily AutoZone sells the rear main with the structure gasket. So that leak is fixed. The clutch looked like someone was afraid to take their foot off the clutch petal. I replaced the clutch with an LuK and put in a brand new flywheel. I am really happy with the LuK clutch, a lot better than I expected and they price was perfect. I had problems with my windows and radio not working. Turns out it was a broken solder joint on the back of the BCM (Body Control Module). Luckily after research i found that problem and that was by far the easiest fix. After all was said and done, 12hrs of work and the car was in tip top shape (aside from no AC) but that is a future fix.

Now...I was driving from my house in Alabama up to a buddies in Tennessee...the car was just fine when i cranked up and started driving, but when i arrived at his home in Tennessee ( 1.5hrs later) i noticed what sounded like a knocking. I checked my oil levels and everything seemed fine. Also, when I am in the engine bay, i can barely hear it, almost non existent. But when I am in the car, its very noticeable. Its almost like an exhaust leak, but it sounds more like valves tapping loudly than it does exhaust escaping, even at the manifold. Seeing if anyone had a similar problem.

Additionally my fuel pump is intermittently going out and i'll have to repair that soon as well. That is causing issues with the car, i believe the pump is weak, and when i push heavy on the gas pedal the car jerks as if its missing, but idles just fine without a miss. I just got out from underneath this car, was really hoping i didn't have to do it again.

 

look for exhaust leak, check exhaust bolts to see if any have worked lose. check spark plugs to make sure they are tight. exhaust leak can cause rich running condition that can cause poor performance. check 02 sensors for fouling. hate to say it but rod knocking can be heard from under the car more so than the engine compartment. one good thing is low mile used 3.8 is easy to find, series 3 will have more hp works fine.

 

I can't comment about all of your issues but I think you have a cracked plug or a short in your plug wires. That would explain the misfire.

 

A throw out bearing could also make a noise similiar to rod knock and being you just did a clutch, its very possible that is the culprit

 

Try listening under the car and see if it gets louder. A bottom end bearing will be louder under the car then under the hood.

If you are sure the sound is louder inside the car it would make sense it’s a release bearing/transmission issue because the sound is most like coming through the trans and shifter. If you remove the sifter cover and can get you hand down on the base of the shifter or on the trans itself you should be able to “feel” the knock if it is coming though the trans.

 

Craby and mfmfim - I will check the plugs, wires, and possibly troubleshoot the coil packs by this weekend. Being that this is my daily driver and doing government work, its almost impossible to take off to drop it off. Not to mention i drive 70 miles each way to work. I do apprecieate the help and I'll check into that as soon as possible and give an update once that is checked.

Cheeks and Gorn - I didn't know that about the throwout bearing. I would have ruled that out considering i just changed the clutch out and put a new throwout bearing in. Now the throwout bearing did come with the LuK clutch, and i have read some reviews that those bearings tend to go out easily, i just wouldn't expect within 500 miles of installation, and i didn't know they would make a knocking sound. It kind of does make sense, because i can feel the knocking in the clutch pedal when i slowly release and rev up at the same time. What would have happened to it to make it knock, and what would it be knocking against, i mean it is only to front and back right?

 

ALSO, and im not sure if this will help anyone give an opinonated diagnosis. But the "knock" does not change with clutch pushed IN or OUT. It stays the same, and the knock speeds up with the RPMs. Which led me to believe either a rod knock. But you have to ask and bounce ideas off people before you start getting dirty.

 

The “knocking” would be coming from either a cracked bearing race or a failing pressure plate. If you can feel it in the clutch pedal there is a very low chance this is coming from a exhaust leak or loose plug. That type of noise will not travel through the hydraulic system very well.
How did the pilot bearing look? Is there any chance that was damaged during the install. Did you listen under the car?

 

The pilot bearing looked to be in flawless shape before we attached the transmission. It is possible it could have been damaged and I wouldn't rule it out one bit. I haven't listened underneath the car yet. I have a good friend who has been helping me work on the car, he has a stethascope so we can listen around and see what the deal is.

 

The 3800's are pretty solid but any GM product can spin a bearing. IMO the issue is GM's rod bolts. In most of the 3800 rod bearing issues without over heating there is a High rev (over 5k) and then the person would let off the gas quickly and let the full weight of the car push against the motor almost like a down shift.

I am not saying thats what happened only that it is the most common cause of rod bearing failure without overheating.