Pontiac Multi Misfire

[bingolth]

I Have A 2000 Grand Am Gt. We Have Been Having Some Problems With It Starting. To Start The Car, The Pedal Has To Be Pushed To The Floor And After 10-15 Seconds Letting It Crank It Fires Up But You Have To Feather The Gas To Keep It Running ,when Started It Will Rev Pretty High Then Drop Then Rev Then Drop. I Had It Put On Code Machine And It Reads Multiple Misfire. The Plugs, Wires, And Fuel Pump Have Just Been Replaced. The Car Runs Good And Strong Down The Road, This Just Happens While Sitting. We Noticed That Having The Air Conditioner On Also Helps The Calm The Motor A Bit From Reving. I Am Good With Older Motors But These Days They Just Have To Much That Could Be Wrong And I Just Do Not Have The Slightest Clue, Does Anyone Have Any Suggestions On What May Be Causing All Of This And If So I Would Appreciate Any Input Thankyou.

[GTP Dad]

Welcome to AF!!

Try cleaning the idle air control motor located on the side of the throttle body. It only takes the removal of a couple of screws to remove it. Spray the pintle with Throttle Body Cleaner allow to dry and put it back on. You may want to remove the entire throttle body and clean it. Neither of these are hard to do and can be done with basic hand tools.

I suspect that the throttle body and the idle air control motor are dirty with carbon and you will probably see a big difference once you clean them.

A couple words of caution, only use throttle body cleaner and don't move the pintle on the IAC motor while it is out of the car.

I would also have the fuel pressure checked. It is possible that the fuel pressure is low due possibly to a bad or leaking fuel pressure regulator. You can rent a guage and check it yourself. Just attach it to the shrawder fitting on the fuel rail. Should be between 45 and 60 pounds to work properly. Another thing, if you haven't done it recently change the fuel filter.

[bingolth]

Today I Am Having The Fuel Pressure Checked But Will Also Try The Other Things That You Have Mentioned. I Really Appreciate Your Input On This Matter. Will Post Comment On What Happened Later Thank You, Any Help At This Point Is Well Appreciated. Thank Again.

[bingolth]

I Had The Fuel Pump Tested And It Tested Good. It Ended Up Being The Fuel Pressure Regulator. Thank For The Info Anyway, It Needed To Be Checked Anyhow....