Hey guys. i am posting this thread to see fi anyone has a flippin idea what the hell is going on with my new car.

16k on her stock

1. Pressure guage going over 140kpa (21+psi)
2. P0420 Catylic Efficiency Low Bank 1
3. When i accelerate my car is ok at first then under boost, starts dying on me. very jerky.

will be smooth smoth smooth, jerk, smooth ...building pressure (faulty reading?) over 80kpa smooth, jerk, jerk, big jerk, fall off. shift to 3rd and the car wants to die.

.....any ideas?. i checked vacume lines, there ok, so far. and i bought it with 15k, with a k&N vortec.

help. throw your ideas in!!!

 

Clogged cat? It has happened to others on here.

 

sounds like a bad cat

 

The stock converter seems to be really hit or miss at the failure rate . Sounds like yours is either clogged or came apart and pieces of it are lodged elsewhere in the exhaust . Keep out boost until you get the problem fixed . Your warranty will take care of it .

 

yep ur cat is fucked, same thing happend 2 me

 

same here...just had cat replaced last week. The tech told me for some reason they use the same cat on the 2.0 as they use on the 2.4 and 2.2. Why, I don't know but I don't think they're made to take the extra pressure from exhaust from a 2.0

 

One reason for catalytic converter failure, a GM engineer told me that if you're having troubles starting your car like its bogging down, don't pump the pedal as if to give it more gas to get it going, it will blow out the catalytic converter. I don't know how many people have done this, but its a no no. Otherwise, it does seem pretty hit or miss, my cat was fine before and after exhaust and intake and stage 2 mods and still is fine since i took it off.

 

well that sounds just great!,lol. i am glas warranty will take care of this problem. of course if thats the problem. but it looks like all of you have agreed.

now my other question is "will this effect my boost guage?" going over 140kpa at 4xxxrpm then bog when it gets that high as well. i believe this guage is supposed to calculate manifold pressure....sooo,yeah doesnt make sense.
god this car goes in on friday and i am even wondering if its going to be possible to drive it down there.

if i press the pedal just a little bit, i have to baby it and throw the clutch in to get her to stay alive,lol

 

clogged cat, its under warrenty so your good. with increase inrestriction ( this would be your clogged cat ) your boost pressure will read higher than normal, and sometimes it will read alot higher. thats all symptoms of a clogged cat. also funny hiss sound when you excelerate.

our cars are fuel injected pumping the pedal before starting does nothing.

 

right on thanks guys. looks like i am getting a new cat. one more question. could there be any damage to the engine while the cat is doomed? i dont think there would be, but the s/c cobalt is still new to me. i used to be ss n/a!

 

sure, the increase in back pressure could harm the exhaust valves. i could see you burning a valve if you really beat on it. take it easy, you should be ok. its driveable, just get it fixed and like silver ss/sc said. try and stay out of the boost/ throttle.

 

will do, thankx. i'll keep you guys updated.

 

for a new cat, you might want to have the one on your car checked. Most reputable shops can do this by checking the back-pressure before and after the cat, to see if there is any restriction. Restricted air/fuel filter are also possibilities for the drivability symptoms you describe, but if your car is throwing cat MIL's/codes, checking the cat for issues is the best place to start. If for some reason your car was running really rich, and excess unburned engine fuel was going into your cat, it can melt down the internal catalysts in your cat and cause it to plug up in a very short time.

My car went into a limp mode (somewhat similar symptoms to what you describe) a couple of times due to excessive engine coolant temperature during the summer, but since I made some cooling mods (read some of my posts if futher interested) it has not reoccured.

If your car is still under warranty, get it checked by a reputable dealer, and the $$$$ (cost) is their problem.

Good luck.

Doc

 

hmmm. thanx. i'll keep that noted

 

im not the the smartest when it comes to cars but i know a little haha so ima go with everyone else Clogged cat

 

Meow

 

Damn GM and their clogged cats! After I killed mine I just welded in a straight pipe and tuned off the 02 sensor. Then the car really MEOWed!

 

16K on a stock car, he should be going directly to the dealership. When it comes to a catalytic converter, I think they're covered up to 100K...

 

Hey guys, updated today! i got my car back today. all the symtoms were indeed becuase of the cat. gm installed a new one under warranty......what the hell is wrong with thee cats?. i asked the head mechanic if this is a problem that occurs frequently with the sc. he siad not really. i asked if there is anything else or other catylic converers out there that would be better. he said " no, gm's cat's are the best you can get" i was like yeah....and your **** smells like flowers.....god.....who else hates dealers?,lol.

pats yourselfs on the back if you were right. another thing to learn from experience

 

p0420 is bank 1 cat is fucked changed one on a impala today. its 8/80 so get it fixed free

 

i love when people pump the gas in there cobalt like they have a carb engine lol

 

try this!!!
hold the pedal down while turning over the engine. doing this turns off the injectors.
i scared the dealer by doing this a while back

 

I'm playing the waiting game with mine. I'll know when it happens! I'm going catless if it does occur. Eff that.