soo, about a week ago i was driving and noticed that my engine sounded a little louder than normal, like I had the window open or something. By Wednesday, any time I pushed the throttle higher than maybe -5 PSIG, my engine putts really loud. Idle is perfect, below that threshhold, she sounds fine. Also feels like it misses a bit in high demand in 2nd and 3rd gears. Any ideas as to what this might be? I'm taking it in on Friday to see waht GM says, but i wanted your opinions so I'll know what to expect it to be

 

exhaust leak most likely. the "putt putt" you hear is probably the air escaping. start the car, get a towel or something and hold it over the tailpipe. you should be able to feel pressure build, and if you stick the towel IN the tailpipe, again you should feel some resistance and it should try to spit the towel out. if you cover the tailpipe, you should be able to hear where the air is escaping from.

 

even though it's only under high demand that i hear the putting?

 

very well could be. think about it. the more you step on the gas, the more air is flowing, which means if there's a leak more air is escaping. a small leak can be totally un-noticeable at idle, or even at lower rpms.

do you have a stock exhaust?

 

yea, it's stock. funny you mention exhaust. it rattles a bit when i turn on the air, and i know it's the exhaust cuz i can hold the tail pipe (only done this when i first start the car rofl) and the rattling stops. maybe a component shook loose? car only has 26k on it and is still within 3 years. i got it from carmax. would chevrolet/GM still do warranty work on the car?

 

first step is to figure out where the rattling is coming from. the big culprit is the heat shield, and is a simple fix. you can just bend it back a little bit. start the car, turn on the a/c, (so you hear the rattling) and lay down next to the car and try to find out where the sound is coming from. but i bet it's a heat sheild somewhere.

also, if it's a heat sheild, and NOT a leak, it would have the same thing. when you turn the air on, there's more vibrations. just like when you give the car alot of gas, there's more vibrations. so that would explain the rattling. but, it wouldn't explain the putt putt sound.

 

so, not the exhaust then?

 

it could be the stock exhaust. read a few posts up, i told you how to check the exhaust.

 

vac leak. Do you have an aftermarket intake?

 

nothing aftermarket except a torque dampener. i've also had it suggested that it might be the cam positioning or timing sensor. is that also possible?

 

first things first. did you check the exhaust or heat shields?

 

Okay... i started off with a putt putt, that turned into a BOOM BOOM...

Check your flex pipe, the kinda coil looking tube that is right past your headers, near the flange...

It is probly busted on the under side....

It started with a soft hiss when i floored it, thought it was cool. lol.. Then it just got worse, and turned into this horrible sound..

Give it a shot, its what happend to me... forced me to buy new headers / dp... i was gonna get anyway

 

won't be able to check until friday, when i can use my dad's tools/jack stand

 

My **** was doing the same thing there was a small pin hole exhaust leak on the front of the cat.

 

Unfortunatly, if it is it, its a reallly hard piece to weld back together.... A very well experienced friend of mine (his ford has 450,000 miles on original engine, and about 50 years of service)... could weld it together, too thin...

He did tie wire to hold them together, because mine got to the point to where it almost fell off...

 

quick update- it was exhaust. the pipe had actually begun to separate from the cat... thanks everyone for their help. getting it fixed under warranty

 

glad you got it fixed. i was pretty sure it was exhaust related.