Starting and Idling Issues

[Cooper04]

I have a 1999 Pontiac Grand Am GT. It has the 3400 V6 and it has 110,000 miles on it. I am having issues with it having a rough idle and starting. It does not always start on the first try. You have to pump the gas pedal to get it to start, (this is one in every four starts). It also has a lope in the idle. I have already replaced the spark plugs and wires, cleaned the throttle body, replaced the fuel filter, pcv valve, and air filter. Where do I need to go next with this. Thanks a lot.

[Ridenour]

Other things could be a dirty idle air control motor, a bad MAF sensor, bad coil packs, or clogged / dirty or leaking fuel injectors.

I would try cleaning the IAC motor first. Do you have any SES codes stored?

[GTP Dad]

Throttle position sensor or the fuel pressure regulator is bad. There is a possibility of a weak fuel pump but if it runs alright after you start it then the fuel pump may not have an issue. Rent a fuel pressure tester and attach it to the fuel rail at the shrader fitting. Generally fuel pressure should be between 45 and 55 pounds at idle. If the fuel pressure is low then replace the regulator first and retest. If the pressure comes up and stays there the problem is solved. If not you may have to replace the fuel pump.

If the fuel pump and regulator check out then the throttle position sensor may be the issue. Search the forum for throttle position sensor voltage readings. You will need to have a digital volt meter. If the readings are not within spec then it will need replaced.