i have a 90 firebird with a 3.1 mpfi
in a a previce post i wrote my car was dying after i fill up the tank well i drove all the gas out tell it was 3/4 a tank full and it runs fine so i drove it down to a 1/8 of a tank and then filled it back up well chevron gas tell the pump clicked and then we drove off and went about 3 miles and then the damm car did it again it lost power then back fired out the intake and would not start had to sit for a 5 to 10 mins then it started big like crap and white smoke came out the tail pipe and it would not go over 2000 rpm then after a few mins it ran fine to get me home i change the fuel filter after the first tank did it but its back

so ppl please give me some things to check before i go and shoot it so i feel better

 

It backfired OUT THE INTAKE?? Something's way wrong there...that's damn near impossible to do on a fuel injected engine. Possible valve damage?

White smoke, for general reference, means burning water.

I'd do a full range of diagnostic checks next time it runs like that, if you can. Check fuel pressure, spark, and engine vacuum. Maybe something will show up as wrong.

I assume you dont throw any check engine lights...

 

EECS system malfuncion symptoms 100%. Period. Solve by DELETING EECS canister (plug fuel line, plug vacuum lines). It's siphoning liquid fuel out your tank in what should be a vapor system. If your fuel tank has been dropped lately, suspect the last idiot who touched it reversed the Return and Vapor lines at the tank.

The only reason I go there is because I bought my v8 at 1/5 KBB value because of this problem and it took me 5 months to figure it out.. the breakthrough was when she was on ramps tilted forward (rear wheels up) and the EECS canister literally DID start siphoning fuel from the tank and onto the ground. That was the "OH CRAP!!" moment. She ran fine ever since I yanked that can.

 

.....You got it dude...that's gotta be it. Congrats on that call.....damn nice diagnostic work there. :yourock:

Just beware of excess vapor pressure in the tank after you remove that. If I'm not mistaken, the EECS system, besides for emissions, was to help prevent vapor-lock.

 

ok i checked for codes i got a code 42 wich could be the igintion modual or the ecm i had the modual tested it failed after a few tests so i bought a new one cause the car would not start now the car still won't start i get wet plugs so its getting gas if i take the plug out it gets a nice dark blue spark but it will not fire over not even a pop just crank crank crank neep help

 

I don't think you can get vapor lock on a FI motor. The pressure from the pump keeps the fuel as a liquid until it is actually spit out the injectors. The only reason for the Charcoal can is to trap vapors that naturally get out of the tank to prevent emissions.

 

i figured it out i went and got the old coil and hooked it up and it started on the first crank so thanks for all the help ppl

 

Okay.. so maybe I will continue to be the only poor bastard who's had fuel pool up under their front left tire thanks to an emissions component..

EDIT still doesn't explain the intake backfire.

 

No, you're right on if someone messed up the lines to and from the fuel tank. If that happened, then you are screwed and you'll get a big puddle of gas, but as long as the system is working as designed, it's only there for emmissions purposes.

A weak coil does explain the intake fire though. If you miss a cylinder or two, then the next time the intake valve opens, the cylinder already has some fuel left in it since the exhaust stroke doesn't totally empty the hole. You can get fuel vapor in there from this and it'll cause a backfire into the intake. The coil has to be really bad though. When my first one went, I had it back fire through the intake a couple times, I thought i had a cracked intake valve, but I was also having the "no power" problem and the revving symptoms that SharpSnake is refering to. REALLY hard starting led me to diagnose the Ignition system, and i found out that I was getting no spark at all, but once in a while I would get a cute little orange spark. Changed out the coil...no more problems, runs like a chimp...uh, I mean champ now.