ok i have some odd noises that are coming from my motor. gonna see if i can get some ideas as to what to check.

1. below 1,000rpm there is a quiet knock. kinda hard to hear but on a quiet night at a stop light in town you can hear it. only happens if i let the motor go over 190* if i keep it below its quiet, but once it goes over the tick is back and wont go away till i let the motor go cold again. have had Rod knock (should be constant and would not go away at higher RPMS) , bad Lifter, and spark knock given to me as possible reasons for it. quiet enough to be masked by the fan, oil has come out clean and free of shavings.

2. growling noise from the rear/lower part of the motor. i have been told this is a normal 2.8 oil pump sound. It has done it for the time i have had the car (3 yrs), and has not gotten any worse.

3. and the newest to me is a ticking sound from the middle of the motor. it sounds just like an exhaust leak but any exhaust leak that i have had be as loud as this i could find by feeling for the hot air around the manifold, None. it sounds like its coming from the injectors but even my old ones didn't sound like this. When the ticking started i began getting this nasty super rich smell from the car.

EDIT: i have checked for fuel leaks and vacuum leaks. Car running and vented out of the shop there is no smell of gas after like 30 mins and there is no visible signs of leaks.

General overall behavior. Starts first flick of the switch 90% the other 10% let it set for a sec with the ignition on and it starts right up. Idles smoothly at 500-600. with a 50rpm or so bobble. accelerates smoothly if on the slow side. have had it on a diagnostic comp and found only the TPS out fixed that. motor sees 5k regularly. 6k if the trans sticks for that long sometimes. Pulls strong till right at 5k, then starts going flat. Gas mileage is at the best i have seen 14mpg babying the the car and driving like a granny, and it normally gets like 8 or so (I drive WOT as often as possible). It can stay with a 3.4 4th gen in good working order tho, right till it sticks on the 2nd to 3rd shift when i have to let of and then only go 1/2 throttle till im over 65mph. turns 2,800ish at 70mph.

Im at whits end as to what is wrong. my only complaint on its behavior is the bad gas mileage. no power + god mileage = cool, Power + bad mileage = cool, Bad mileage no power = just plain sucks big fat ****. The noises aren't good either but i can't figure out what they are.

Oh and i have read every new post here in the V6 section or at least glanced over it for like 2 years so.... no USE THE SEARCH BUTTON replies please.

 

I'm not an expert on these cars yet, but my engine did all kinds of weird stuff when I first got it. So I have the chevy dealer replace the following: (I don't do much myself, just oil changes, filters, and plugs, belts etc)

Mass airflow sensor (if you got one, I don't)
Throttle position sensor
Manifold absolute pressure sensor
Coolant temperature sensor
Exhaust oxygen sensor
Crankshaft position sensor
Camshaft position sensor

She runs quietly now but there is still a vibration. Probably just timing.

 

noise and bad mileage may be from bad o2 sensor im not an expert either but my grandfathers truck along with a few posts on here have noted that if your 02 sensor is bad then you will get terrible mileage

 

If it's quiet enough that you can only hear it at idle and it's coming from below the manifold it's either your injectors or lifters, check both. Replace the maf if you haven't yet (get a new one, reman will go bad quickly) and dump some injector cleaner in the tank.