My car seems to go limp in boost and hitting 5.5k+ rpms. It is fine up until then. Someone on Facebook suggested that it might be my charge pipe being loose, but I toyed with it in the garage and it didn't feel loose. Someone else said it might be my Cobalt's learn down feature slowing me down because I haven't gotten tuned since installing a cai, but I've had this intake on since 2011/2012. I don't think it would start affecting the car now after so many years, right?
Anyone have any clue what might be causing it? CEL is on, but it's been on because my cat is bad. No code for whatever is happening now.

 

would not a clogged cat have an effect on performance?

 

True, but the CEL has been on since January. It's driven fine all this time until now. Maybe it's gotten far worse over the months, though..

 

Give us the code

And yes if your cat is clogged you would notice huge performance loss.

Miles on car?

 

Intake valllves....

 

Did you change your spark plugs recently? If so the wrong gaping can also cause this in the high rpm's

 

What are you boosting to. Intake valves could also be a culprit

 

I'll check the code later today and post it up. The car has about 121,7XX miles.

Changed spark plugs back in January.

How can I check the intake valves? I'm still a noob at car maintenance.

 

You will need a borescaope like this 5M 6 LED Waterproof USB Borescope Snake Inspection Endoscope Tube Camera Mirror | eBay

Then you will take off the brake booster line from the front of the intake manifold. The nipple the brake booster line attaches to will unscrew from the manifold.

Insert borescope and record with computer.

 

year, mileage, mods, tune? What gas do you run?

 

The code is P0420. That's the catalytic converter code, no? I have a spare catalytic converter downpipe sitting in my garage that I'll need to install soon enough. Hopefully it's good. I bought it off of another Cobalt SS owner on this forum, but he said he bought it from someone else and never installed it.

2009, ~122k miles, only CAI so far, no tune yet, run 91 octane.

 

P0420 is the cat code for sure. You sure you don't have aftermarket downpipe already?

Also, have you ever cleaned the intake valves? IF you haven't, it's time.

 

A clogged cat will totally hamper your top end performance. You might even start to experience insane cylinder head temps if the Cat really can't get the exhaust gasses out fast enough.

And your intake valves are probably going to look like the grease trap on a fast food deep fryer at 122,000 miles.

 

take the downpipe off and have a look, replace with catless for $200 and enjoy the sound and performance.

 

Legally can't. I live in SoCal where it's illegal to have a catless DP. I'm considering doing it some time after my smog check this summer, though, and replacing it every two years with the stock one when the smog is due.

 

#yolo just throw stocker back on for emissions.

 

I can only imagine how bad valves with 120k are. Mine had a quarter inch of build up at 58k.

 

catless downpipe is illegal in MA too, i pass inspection with it fine. Worst case scenario if someone eyeballs its ill swap to stock.

 

Doubt you pass a sniffer though.

Otherwise it's nice to just gut the stock cat to pass visual.

 

How do you clean the valves? Seafoam?

 

You have to pull the intake manifold off and blast them with walnut shells, chemicals and a brush, or a combo of both.

 

It's not simple.

 

Costs 100-200 dollars depending on what tools you already have. Takes about 2 days of work. It's not hard but it's not for people with no auto skills. Should be someone in socal that could help though.

 

Bash the inside of the cat out.......you'll still technically "Have it on the car". You'll have to deal with tuning for the fueling, etc afterwards of course.

 

Okay, I'll ask around in the Ecotec group I joined on Facebook a couple weeks ago for help or see if anyone with some skills wants to help. I'm definitely not mechanically inclined to do this ****. If worse comes to worse, it's time to bust into the small amount of money in my savings and pay a mechanic.