Davisthabeast

My car broke down a month ago and refused to go more than 20 miles per hour. At first the amutuers at advanced auto told me the problem was as simple as spark plugs and I believe them. After replacing the spark plugs in the freezing cold I relized that was in no way the problem. I proceeded to change the coil pack, due to a misfire error code brought up by the MODIS scantool used at my school (ATI). After that I got mad one of my door locks was cut in half on the inside, so when I pushed it down the only way to get it to pop up was using the key. I yelled at the class working on my car, thought it turned out to be a repair overlooked by the insurance company. Thats another story. So here I am, the car has made no improvement with the previous repairs. It will not make it to an advanced auto on its own to be scanned.

Like when it first happened, when the cars driven for 5 minutes or more the top speed decreases from 20mph to 5-12mph and thats when I chose to park it on all test drives.

Since people like to give smart ass comments about what should've been done, and ask questions to answer my question, I'll make this simple and put it in ASE Form for you experianced mechanics to avoid making the more complicated.

(The above is being discussed with these symptoms):The 2.2L Ecotec engine of a 2005 Cobalt LT is knocking while idling, and is running noticabley rich. Technition A says to replace the catalytic converter with one of these (http://www.autopartswarehouse.com/se...294965326+9190), Technition B says to change the fuel injector (or pump??) with one of these (http://www.autopartswarehouse.com/se...rolet%20Cobalt). Who is correct?
A?
B?
Both?
Niether?

And im more worried about what fuel pump to put on if thats more likely the problem.

light'bolt

I'm assuming no codes were thrown besides the misfire and the MAF sensor and throttle body are all cleaned and in good working order. I'd check the cat first.

To check the cat, drill a small hole on the exit side of the cat and check the air flow with an air flow meter if you have access to one. To check the entire exhaust, just feel the end of the tailpipe and see if it has a good flow. If your satisfied there is sufficient flow then have the injectors checked, and then the fuel pump.

Coblasts

They both could be right.
Im going to explain my answer.
Leaking injectors will cause your cat to fail by causing a melt down of the core due to the raw gas burning inside the cat.
Misfires should of brought up a code and if bad enough the Service light should be flashing when the car is running.
A cat that clogged should cause a cat inefficency code.
If it is the cat that clogged you should be able to drive it for a bit at night and on a dark street look at the exhaust manifold and it will have a red glow to it(Red hot)
Are you sure someone in the shop class didnt sugar your tank,
You come across as someone with a attitude.

rukkee

iTrader: (3)

Pull the o2 sensor out before the cat and see if it runs any better . We did that to a couple of 3.4's to find the cat was plugged.