Hello, new here, any help will be greatly appreciated.

I own an '01 GT which up until recently I have had no problems with. This all started after I took my car to a not-so-knowlegable, when it comes to aftermarket parts, mechanic. Originally the intent was for him to check for an exhaust leak, loose headers, or possibly a blown head gasket (though I was not overheating or leaking antifreeze) as I heard a faint hissing noise. He took it upon himself, however, upon hooking up his computer to replace my O2 sensors and EGR sensor (to get my check engine light off). He was successful, but it only lasted for about 10 miles driving distance before it popped back on. Anyways, since these changes were made my car has really been acting up. Once it heats up about 1/4 of the way the problems start, the RPMs will ping dramatically, sometimes bouncing from about 700 to 2k, then drop to almost <300. Once fully heated it isn't quite as apparent, usually a steady ping from 400 - 800 while stopped. Turning on any accessories (heat, lights, etc) worsens it moderately. Oddly enough, when I fill my tank with gas is when it is the worst. Normally right after filling my tank it will die 2 - 3 times before it will come up to a reasonable RPM and let me putter off, this is regardless of cold or fully heated engine.

The car has a mac cold air intake, mac headers, magnaflow exhaust, no catalytics and a mac prochamber..which is why I believe my CEL is on, after installing Mil eliminators and resetting the computer it continues to remain on, fiddling with the intake while the car idles makes it even more erratic, but I can't seem to narrow down my problem -- bad O2\EGR?, fuel pump?, clogged hoses? Before taking it to a dealership I was hoping to get some tips that may lead to a more simple (and cheaper) solution. Thanks in advance.

-E

 

try disconnecting the negative battery cable for at least 15 minutes to clear the KAM (keep alive memory) in the ECU and then reconnect it and see if this doesn't help you out some. anytime you change something like a sensor or engine control item, you need to do this to let the ECU reset itself and learn the normal range of the new input signals it will be seeing from the engine sensors like the O2 sensors so it can properly react and control the engine, especially at idle speeds.

 

You might want to look into removing and cleaning your idle air control valve.