I have a 2001 Monte Carlo S.S 3.8 engine and about a week ago it started shaking a lot when I started the car it would shake a lot and then the check engine light came on so I took it to AutoZone and had them run the codes and nothing came back no error codes at all! Which makes no sense since the Check engine light is on. My husband changed my spark plugs and wires and changed the fuel filter because I noticed when I'm at a stop light and start to give it some gas it feels as if it wants to die. It doesn't die but it shakes and sputters like it wants to die. He also took my throttle body out and cleaned it and cleaned the MAF sensor but nothing has made it any better! I also bought a catalytic converter cleaner the kind you put in your gas tank to see if that helped but it didn't help. Does anyone have any idea of what could be causing this? We have checked for vacuum hose leaks and there isn't any obvious leaks that we can see. Any other issues that we can look into? Do you think that it could be that we need to completely replace the throttle body it was really dirty and black with carbon when my husband removed it and cleaned it with Throttle body cleaner. He said that he doesn't think it needs to be replaced since it's clean because of it being a older model throttle body it's a Manuel type and not a electronic throttle body or at least that's what my husband says idk if he actually knows what he's saying or is he just saying that because he doesn't want to waste the the money to buy a new one. Lol! Any advice anyone can give me would be greatly appreciated!

 

Some auto parts stores still do it for free (in the hopes that they can sell you the parts to try to fix it). That would be the quickest / easiest route.

 

The fuel pressure regulators are bad after many years of the diaphragm leaking fuel into the vacuum line. Maybe that is causing it to run rich and give issues? Take the vacuum line off the pressure regulator at the front right of the engine in frontt of the intake and see if the regulator is spitting out gas while it is running.