Out1aw

iTrader: (1)

My 1999 Grand Am GT (3.4) has been in and out of the shop for the last 6-8 months having everything redone, but we STILL cannot figure this problem out. The car is at my uncle's shop right now, but we are wanting to pick it up and fix the problem ourselves (my father and I). THe problem is as follows: The car will sometimes crank, but when it doesn't fully crank, it turns over, sputters, and pukes. When it does this it floods the cylinder heads with fuel for no reason. We believe it is a PCM controlled-thing, but everytime my uncle plugs the scan-tool or programmer to it everything checks out fine! There are no codes being thrown, and when it is running it runs perfectly! The current mods are Intrax springs, flowmaster cat-back, de-screened MAF, and new speakers with a cd-changer. Please give me ANY valid suggestions or hints! Thank you.

- David

aux_fast_cam

My mom had a lumina Z34 with a 3.4L motor it sounds like the same thing it would do. This car was weird it would only do this maybe once a month maybe less. If it started fine it would hit after the motor rolled over once, but if it didn't hit right off it would flood itself. We started treating it like something with a carburetor. If it didn't start right off hold the accelerator pedal to the floor and it would start. Was always a flooding issue like it was holding injectors open too long during cranking. Maybe try next heat range of spark plug ie hotter plug.

wait4me

iTrader: (10)

Crank or cam trigger.

joecar

Possible causes:
a. ignition module is starting to fail.
b. crank sensor is starting to fail (triggers a. directly during starting).
c. leaking fuel pressure regulator (punctured diaphragm); pull vacuum hose, is it wet with gas...?
d. leaking injectors; connect pressure gauge to fuel rail, turn key to on, does pressure not hold steady...?

jyeager

One or more injectors sticking open? The symptoms you describe sound just like a flooded engine. Imagine an injector stuck at 100% duty cycle while trying to start...it would turn over, stutter, and puke with lots of fuel loaded in the cylinder head.

Now if you can somehow figure out if it's just one injector or all of them...

Out1aw

iTrader: (1)

Well, turns out the TB Position sensor was the problem. The butterfly valve was opening too much when cranked, therefor flooding the motor with fuel. Now the problem is it cant hold an idle... its got a brand new IAC... what else could this be?