So my 3800sc Fiero had been misfiring when hot and I get on the throttle. I replaced injector o-rings, sc gackets, plugs (2 steps colder), and wires and it seemed like the problem went away. I brought my car to get aligned, took it for a drive after and it was doing the misfiring thing again. Brought it home, scanned for codes, went for another drive and it ran for about 40sec then dies completely. It will run for a split second when I try to restart it but dies right away. Giving it the gas once it starts kills it instantly. Seems like it may be fouled plugs. I also noticed the car ran quite rich even before the misfiring problem. Any ideas what to check first.

The car: 3800sc 86 Fiero with 3.25 pulley, intercooler, 195 tstat, 3 in exhaust

I would start by checking fuel pressure. Sounds like the symptoms of a dying fuel pump or the short rubber hose in the tank from the pump to the hard lines. If fuel pressure is good I would move on to checking the ICM and crank sensor.

I have a fuel pressure gauge on the motor so I can't tell what its doing while driving. But when I turn the key on to prime the fuel system I get normal pressure. Whats the best way to check the ICM and crank sensor.

Does the fuel rail hold pressure or does it drop back down after prime ? Crank position sensor should put out AC voltage while cranking, not sure haw many volts, but its not much. ICM I have no idea how to test, I think most parts chains can test them for you. I just go to the U pull and Pay and grab a couple spares to keep handy for swapping.

Any chance your dealing with a VATs/PASSKEY problem that started up by disconnecting the battery? If the VAT's PASSKEY fails while the engine is running it fails in a unlocked mode, and when disconnecting the battery, the VAT's/Passkey starts off in a locked mode. In locked mode if it doesn't get the right passkey signal, it will start and then turn off shortly.

I had VATS disabled. The fuel pressure will drop to around 20 in like 10sec then it seems to drop very slowly after that

quote Originally posted by Bfisher31286: I had VATS disabled. The fuel pressure will drop to around 20 in like 10sec then it seems to drop very slowly after that

FP should be a cocstant 42# at idle and go up as th motor is revved. Soungs like u got fuel pump issues...What pump you using? Combine this with that 3.25 pulley and u will be looking or a new motor soon...

I have a Warlboro 255 in there. My fuel pressure is 47 with engine off...somewhere around 40 at idle. How quick should pressure leak down in the rail after the initial prime? I get plenty of fuel (pig rich at WOT) and now it smells like tons of fuel when I try to start it and it dies right away.

quote Originally posted by Bfisher31286: I have a Warlboro 255 in there. My fuel pressure is 47 with engine off...somewhere around 40 at idle. How quick should pressure leak down in the rail after the initial prime? I get plenty of fuel (pig rich at WOT) and now it smells like tons of fuel when I try to start it and it dies right away.

Leak down after you start then kill the car? If that is what you mean then I have seen this all over the board with differant fuel pumps. Does your FP go up when you rev the motor? Sounds like maybe you have some vaccuum leaks on the motor. Is the vaccuum line to the regualtor still hooked up?

Also, what have you guys done with the pulsator on top of the fuel pump? I left it in there when I installed the pump, but the way it is just stuck in there with some o-rings doesnt look like it could hold 40-50 psi

quote Originally posted by Bfisher31286: Also, what have you guys done with the pulsator on top of the fuel pump? I left it in there when I installed the pump, but the way it is just stuck in there with some o-rings doesnt look like it could hold 40-50 psi

I use FI line instead of the pulsator....

I agree a piece of fuel line a 2 hose clamps,to replace the pulsator (the hose clamps will prevent your fuel pump from poping off,I had this happen after hitting a pot hole,fuel pump poped off and the engine died).

So the start then die issue was due to a bad MAF. I had a feeling it was engine electronics related so I started unplugging sensors one by one. When I unplugged the MAF it started but ran somewhat poorly. Replaced it and it starts and runs great. I still haven't driven it enough to see if it cleared up my misfires.

Thanks for following up with your cure, this thread just may help someone in the future now !

Glad you got her going again !

The misfires are due to fouled plugs. I did a leak test and found out I had massive leaks at the intake gasket under the supercharger, it was a miracle I was making any boost. That is what is causing it to run rich and foul plugs. Will be replacing gaskets and attempting to fix all the leaks soon.