my car... 1997 trans am, mods- long tubes, ory, cat back, moroso intake, vortec elbow, msd wires, ngk tr55 plugs, and still has all emission stuff... today the car was driving fine, it was about on empty when i was heading to the gas station... my check engine light came on and started flashing (misfire???). so i scanned the codes when i got home and it came up with p300 ( multiple misfire) and p 441 (evap system flow during purge) the car is running horrible now and you can smell alot of exhaust like its running rich... does anyone know what causes this and how to fix them???

 

check your plug wiring. same thing happened to me, i ended up having a plug toughing a header and it melted to the core wire. it caused the misfire.

lol btw u should fix your signature. you have a 97t/a and ur sig says 99 t/a?
two diff engines lol

 

my sig says the 1999 trans am because i have 2.... a 1999 ls1 with just a cat back and n2o and my 1997 as stated above....

 

anyone else have any ideas??? i just looked at the wires some and they all look ok...???

 

also if it matters it has a 3800 stall in it with a built tranny...

 

how are the plug wires routed... make sure they arent burnt.. with my LT's i went through two sets of plug wires before i went to Over The Valve Cover wires.... keeps them away from the headers...

 

where can i find the setup for over the valve cover wires????

 

I would look more at your question...It was running OK, but then when almost empty, it went down hill.... My $0.02, there's something amiss in the fuel system.

Fuel pumps like to be submerged in gasoline. It helps keep them cool. Also, running that low on gas, maybe some crud got sloshed around the pickup, and either is blocking flow, of even got into the filter. Or, if you had some water in the gas, it finally got to the engine, as there was not much fuel in the car.

First quick and easy thing to do, is replace the fuel filter, and add some dry gas.

 

i already got gas... nothing changed when i filled it up tho...

 

You said you got a code for the EVAP System. What that System does it take the extra pressures that the gas makes in the tank, and burns them vapors. It always burns a little bit of them everytime it runs, just to keep the pressure down, eventhough after you drive it hard and go to the gas station, you hear it breathe when you open the gas tank. I think it didn't pick up enough vapors in it's cycle, and it started to messup itself. It has to burn a certian amount. It might be sending in more fuel to burn, sensing that it needs it, when it really doesn't. It hasn't reset itself. Your best bet would probably disconnect the battery for an hour, and let everything reset itself.

 

elitesparkplugs.com

thunder racing has a kit also i believe

 

STILL NEED HELP ON THIS.... I took the car out today and it was fine untill it got up to operating temp then started missfiring bad again... i went home, put some injector cleaner in it and did a fuel filter... the old one was plugged when i took it out, i put the new fuel filter in and then went over every plug and wire to make sure the plugs were tight, and the wires werent melted from the headers... last week i put new ngk tr55s in so could it have fouled a plug or is this something else from what it sounds like??? Like i said up top tho its only after the car gets up to operating temp then it will missfire..... someone help...

 

Buy a new gas cap...

 

i will try my fiances new gas cap today but that doesnt seem like the problem with this... would a gas cap cause a bad misfire and for the car to have less power...

 

Like I said in mine, I would disconnect the battery and let it reset itself, there is an adjustment off...

 

i will try that too today...

 

Might work, might not, I would try it though.

 

i dis connected the battery for a few hours this morning... then i put my fiances new gas cap on it and drove about 30 miles... the problem was still there... could this be a bad fuel pump or a bad opti spark....