When driving normal the car runs fine, but when I run it hard, it hesitates, sputters, and acts like it wants to back fire. Over the last couple of months, I've cleaned the injectors (lots of carbon) didn't help, replaced the pre-converter O2 senors didn't help, and cut off the cad converters. Still runs like crap when pushed. Any ideas what to check next?

 

does it throw any codes? that would be a good place to start. if not, it could be a bad maf, tps, coolant temp sensor, or most things in the engine, really

 

could also be a plugged fuel filter or a pump going bad.

maybe get a fuel pressure guage on it. Try new plugs?

Also clean the maf, or better yet; see if you can swap with a know good one.

 

try checking the pluga and wires also check for any type of leaks such as: exhaust, vacuum, ect..

 

definitely check for small vacuum leaks or exhaust leaks. an exhaust leak before the 02 sensors will cause a false lean making the car run rich.

 

First off, thank you for the replies. Update:The SES comes and goes. Usually when it is on, it's O2 sensors. My guess would be where I cut off the converters. Leaks and plugs are next. It's an automatic, so most bog downs occur before and/or after a shift. I heard the plugs are a pain. The 8th almost impossible to get to. Any suggestions? The SES just came back on. Took it out today, floored it, and couldn't break 40 MPH. Passing gear will engage, but the car doesn't go.

 

Did you check the fuel system? As Rod 442 stated a plugged filter or bad pump could cause your symptoms.