I was wonder what are the symptoms of failure because I have been around and around the dealer in Liberty, MO again and Excelsior Springs, MO..... and they will not look at anything mechanical only sensors interest them and say and I quote, "WE CANT FIND ANYTHING WRONG." The problem that I'am having is when i get on it, the car has a hell of a time getting up to 100mph and struggles to get to 120mph. I have hooked the car up to my laptop under a program called "DIGIMOTO" found at digimoto.com gives detail in on the fly. Shows the computer is limiting the throttle back to 88% and and bunch other crap dealing with F' ing sensors... Its a F$$K$@$ joke that 2 dealers don't know what the hell is going on. One dealer even changed the lower limit Baro Sensor. They said it was open. Its pissing me off severely. This is what i have told them over and over. My symptoms that I have are the following. 1. On cold idle the supercharger sounds like rattling marbles inside. 2. Lacking serious performance and hesitation at high rpm(5500rpm). 3. Severe vibration coming from the most front part of the engine(supercharger)@ 4000rpm. 4. Boost has gone ranging from 12-13psi to now 17.5psi at 99% load, and not to mention crappy fuel mileage. No modifications have been made. And also when you hit the rev limiter it sounds like its couching through the intake. HELP!!!

 

That smells a lot like a bad cat. Usually techs use the sensors to diagnose the problem an if there's no problem with the sensors then they may not be interested in checking mechanical problems. Could be the supercharger as well except that they are pretty tough to begin with.

 

idk if you would wanna do this... but take the supercharger off and check to see if it sucked anythign up.

 

Struggles up top and boost spike..

x 2 Bad Cat

 

bad cat fo sho

 

the comp recognizes 88% as wot in many cases...this is not a problem.

backpressure from failed cat could cause excess boost and lost performance.

give that a check.

 

Yeah, defiantely sounds like a bad cat. The increased boost and sluggish performance is normal with a clogged cat.

1. On cold idle the supercharger sounds like rattling marbles inside.

This is the coupler. How many miles do you have on the car? It is normal for the SC to get noisy as the coupler wears.


2. Lacking serious performance and hesitation at high rpm(5500rpm).

Bad Cat


3. Severe vibration coming from the most front part of the engine(supercharger)@ 4000rpm.

?? Could just be vibration from the engines, compounded by the back pressure from the bad cat. I always get vibration from the engine, and always have.


4. Boost has gone ranging from 12-13psi to now 17.5psi at 99% load, and not to mention crappy fuel mileage. No modifications have been made.

Bad Cat. I could be possilbe that there is another restriction besides a clogged cat, such as a broken/stuck valve... but the cat is much easier to replace (and usually the problem) then tearing into the engine.


And also when you hit the rev limiter it sounds like its couching through the intake. HELP!!!

I have no idea about this one... couching through the intake?? This one confusses me. My advice... try not to hit the rev limiter.


P.S. 88% = full throttle on the cobalt.

 

Finally after dealing with "a hole" after "a hole" I have an answer, Superior Chevrolet in Merriam, KS Found the problem. Severe manufacture defect. 3 rocker arms had come loose on the exhaust cam interns a damage cam lifters and which explains all of the above. I give Kudos to the techs and dealership to take the time to diagnosis my "Coby" and my baby. https://www.cobaltss.net/forums/images/icons/icon10.gif

 

Glad you got it fixed!

 

Superior Chevrolet FTW! I wish I was still in Olathe, they could have figured my problems out 10x faster than this crappy Cali dealer!!!