new here, having some major issues, please help

[zjstuff]

i have a 99 grand am se 2.4.

i was having a few minor issues to start, then it just went down hill.

was dumping too much fuel, ended up replacing fuel pressure regulater, throttle positioning sensor, ignition coils, ignition module tested good, plugs (put denso plats in), boots.
everything seemed good. about 2 or 3 weeks later, the cat clogged up pretty bad.
i replaced the cat, o2 sensor on cat, put a new exhaust on it ( 2 1/4 pipe ) all the way back, and put a cheep muffler on it.

it sits and idles fairly well, at about 1.7 - 2 thousand rpms its a bit rough, but smooths out after that when just reving it up. the cat gets red hot but there is no loss of exhaust flow. when driving it, there is no power, skipps pretty good, stalls, sometimes backfires and it mainly feels like the cat is still clogged up.

i've re-replaced the spark pluggs, 2/4 were black as hell. i've been told that it seems like there could be bad gas (has been sitting a while), dumping too much fuel, or a timing issue.

would a bad o2 cause anything? what do you think?

[xeroinfinity]

Welcome to AF !!

If you havnt been adding injector cleaner regularly(every month), or had the system profesionaly cleaned, I'd test your fuel injectors and check the fuel pressure regulator & pressure.

to test the injectors on your 2.4;
Testing the injector resistance using an Ohm meter acrossed the injector terminals, should read between 1.95-2.3 ohms w/EGR and 11.4-12.6 without EGR.

Fuel pressure should be between 41-47 PSI w/EGR and 52-58 psi without EGR.

Even a clogged fuel filter can cause simular issues.

Hope that helps

[alconk]

They didn't install the cat backwards did they??

[zjstuff]

nah, it was a direct fit cat. i'll check on that fuel filter xero. i thought i was having some problems with it before and had it tested, it was good. problem was the fuel pump relay, thats why i didn't think anything of the filter.

[3100]

If you have any codes that would help.

[zjstuff]

codes were random multiple cylander missfire, and evap emissions control system malfunction.

[3100]

find vacuum diagram label under the hood. Make sure all the vacuum lines are connected and in good shape. Especially check the evap solenoid vacuum line for tight connection.