sammy58

I have a 2002 firebird formula motor is completly stock except for slp ram air intake, and borla catback exhuast, when is cold outside ill start my car and it idles very rough until it get to operating temp. replaced mass air flow sensor, coolant temp sensor, all o2 sensors, tps sensor, new plugs and wires, and tips plz car has 88,000 miles

Camaroo1

Check the intake manifold bolts.............betcha they are loose. Let me guess, it starts up ok but runs rough for about 2 mins then smooths out and runs ok?

sammy58

Yes thats exactly it but i had it put on a smocke machine and they couldnt get it to leak anywhere

Camaroo1

Trust me on this your intake bolts need tightening .....after the engine warms up it seals better. Cold its leaking ALOT of unmetered air in causing all the cylinders to missfire. After it runs a few mins the computer switches to using the O2 sensors and thats why it smooths out. Cold its running on the cold start programing which has NO allowance or way to add more fuel to compensate for a air leak so it goes lean and missfires. As it warms up the intake also seals better so like magic the problem disappears........

The problem with the smoke machine is its only as smart as the guy using it.......If they didn't check it with the engine stone cold they completely missed the problem!


I don't make this stuff up to give my keyboard a workout ya know.......

sammy58

hey sorry took so long to reply, the mechanic changed intake gasket and cleaned fuel injectors and still does it, any other sugjestions.