over $500 and the problem still exists!

[idontknowhow]

I've replaced both in-tank and in-line fuel pumps, cleaned the idle stabilizer and throttle body, changed the air filter and spark plugs and wires and checked all of the vaccume hoses for leaks and clogs. and I have ran the car on premium fuel with injector cleaner. The car still sputters and hiccups, when first started it runs fine for a bit but after around 30 seconds the rpms start to go down and the engine sputters around, and when i push the gas the engine stalls a bit and the rpms go down and it backfires in the airbox, after pumping the gas i can get the rpms up enough to drive it, i'm completely stumped. any ideas?

[idontknowhow]

oh ya and a gas and oil mixture leaks into the airbox but all crankcase ventilation components are clean and in good shape

[themagellan]

Have you checked the timing?

You would also be amazed at what a few new properly made grounds will do.

[alaincopter]

Both a bad coolant temperature sensor or o2 sensor could cause this. Have you looked into these sensors?

[sippin.fnordies]

Both a bad coolant temperature sensor or o2 sensor could cause this. Have you looked into these sensors?

agreed...
on the bright side, you have already taken care of the fuel system on your car...something we all end up doing sooner or later.

[myboxyfox]

Have you checked the distributor? I had a car with simular simptoms that had a loose rotor. It would pop up once in a while and the car would barely run and backfire into it's air filter/

[novws]

My car was experiencing similar symptoms when I got it. It needed timing reset, a coolant temp sensor and an 02 sensor. Not saying those are definitely your problems, but might be worth investigating.