Hey guys,

I would appreciate some advice. I have a 97 Z28 that has had the following replaced in the last 6 months, new fuel pump, fuel filter, air filter, spark plugs, wires, battery and starter. The car has a miss when idling and also stumbles upon acceleration. If it has been driven recently, it starts up perfectly but if I let it sit for 24hours with out driving, It acts as if it is flooded and will not fire even though the starter keeps turning it over. It also smells like it is running rich (fuel smell). The codes I get are PO300 (random cyl miss) and P0441(Evap... incorrect purge flow). The check engine light frequently starts flashing while driving. I am not sure what my next step should be to diagnose the cause of the stumbling and flooding. I would love some guidance on this matter.

thanks,
Art

 

Need to know whats all been done to the car. Adding a "signature" is the best way. You should check the fuel pressure and take it for a drive and see how it does. Did it act this way before the replacement of parts or get better or worse? How many miles?

 

Thanks for the Reply. The car is in stock form with 130K miles. It was running well for a few months after the fuel pump and filter replacement and then started to develop a slight shudder upon hard acceleration. Soon after that I parked it one evening and the next day it seemed like it was flooded and would not start. The first thing I did was change the air filter, but that didn't make much of a difference. The plugs and wires hadn't been changed in a while so I went ahead and changed those out (AC Delco double plat). With the new plugs, the car started right up nicely but when accelerating and even when just cruising along it stumbles intermittently and the check engine light will start flashing and then stop flashing. When idling you can tell that there is a miss as the car shakes a bit, even though it keeps running. I was also getting some occasional noise from the catalytic converter, when the car warmed up but that seems to have subsided. You can smell fuel in the exhaust and when I don't drive it for a day or two, it is very hard to get it started as it seems to be flooded. To get it going, I usually take the fuel injector fuse out and crank it to try and clear things out. I then replace it and try to start again. Usually have to repeat this cycle 3 or 4 times before it finally catches and then it starts up rough but once I rev it a few times it clears up and runs.

 

Sure sounds like it could be fuel related. I have heard of pumps going back quickly and it could be other issues with the fuel system. Read these for help with the one code. Check that fuel pressure for sure and while driving. maybe your opti is going out also. Many things it can be including a plugged cat.
CamaroZ28.Com Message Board - Search Results

 

Next time you try to start it after it has been sitting, put the accel pedal on the floor BEFORE turning the key to start, then hold it on the floor until the engine starts. That puts the PCM in "clear flood" mode. If it starts faster with the pedal on the floor, could be leaking injectors.

Check the fuel pressure when the pump primes (turn key to on, don't start the engine). Should peak above 40psi when the pump shuts down, and then should hold the pressure for a while, and not drop rapidly. Rapidly dropping pressure could indicate leaking injectors, faulty fuel pressure regulator, faulty check valve in the fuel pump, or a leak in the lines, including the flex hose for the pump inside the tank.

 

Thanks for the advice guys. I definitely need to check the fuel pressure. In regards to starting it up, I originally tried the "holding the pedal to the floor" trick but for some reason my car doesn't respond to it? If I have the pedal down it doesn't even seem to try and catch. I have had better luck with removing the fuel injector fuse and doing a normal start attempt, followed by replacing the fuse and trying again. This morning it was flooded again and when I finally got it started, there was a fair bit of white smoke from the exhaust which took about 5 minutes to clear out and go back to normal.

I should also mention that my car is a 6 speed manual