runs fine at idle, but backfires and dies with gas???

[will1975]

Ok here is my problem. I have an '84 vette that runs great most of the time but every once in a while it will backfire and die when you give it a little bit of gas (will still run fine at idle). Last time it ran perfect for 3 weeks before leaving me stranded (thank god my buddy has a ramp truck). I was going through all of the old repair receipts from the previous owner and there was one that it was towed because of the very same problem and they replaced the fuel pump. I was also reading somewhere (wish I could remember the site)... that suggested replacing the 84 pump with one for an 85 to give it more pressure. I guess this is basically a two part question, would a bad fuel pump account for the backfiring or does this sound more like an ecm problem? And secondly does replacing the 84 pump with an 85 make any sense to anyone and is this something that anybody has ever heard of doing or heard recommended before? I suppose I should get my hands on a fuel pressure meter to find out for sure but I was wondering if anybody had encountered this problem before... thanks a bunch in advance for any help anybody has to offer.

 

[JonM]

Here is the site you were talking about. http://www.crossfire.webhop.net/

As for your problem, have you checked your plugs, fuel filter, wires, timing, cap, rotor and HEI module? The fuel pump you have is fine...84's only need 13 psi...have you checked for any stored codes?

I suggest if you are going to work on a 20 year old car you invest in a manuel...http://www.helminc.com/helm/homepage.asp?r=

 

[will1975]

Yeah I actually bought a manual within about a week of owning the car. Also I originally thought it was some bad gas or water in the tank as it seemed to do it every time I filled up the car so I drained the tank and replaced the fuel filter but didn't help it any. Also cap, rotor, plugs, wires are all new and timing is right on, didn't change the module though... haven't pulled codes either, is there a cheap code reader that I can buy somewhere or should I just take it someplace and have it hooked up?

 

[rrhayden]

My 92 experienced a similar problem a couple of weeks ago. It turned out to be a plugged fuel filter. I replaced it and now she runs fine

 

[JonM]

Will...The cheapest code reader you can buy is a paperclip...bend it into a U shape...looking directly at the ALCL, stick the clip into the upper TWO (A & B) right hand connectors...turn ignition ON do not start...look at the Check Engine light...it will start flashing...it will flash a code 12 three times X=1 flash. X XX, X XX, X XX, any codes after that will also flash three times...example= Code 34...XXX XXXX, XXX XXXX, XXX XXXX That is all there is to it.

 

[84brzvette]

I have a problem similar to that, but mine likes to stall when I let off the gas quick in 1st gear. But its only when I punch it off the line then let go around the end of 1st begining of 2nd. Im not to sure why it does this, and im not sure if Its a big thing. Ive recently replaced the fuel pump, plugs, wires, and ditrib. cap. It still does it though.....

The fuel pressure is fine.... anything else I sould check?

 

[will1975]

update....

ok after doing alot of searching through the use of the wonderful search button and this super site I was able to narrow it down a little. No trouble codes in the computer and it was getting plenty of spark so I figured it was either a fuel pump or a plugged cat maybe. Well since I wanna add an x-ram intake and a bunch of other mods anyways I upgraded to the 85 fuel pump from the 84 as the 84 doesn't supply enough fuel for the horsepower i wanna achieve (plus the price tag on the fuel pump was much cheaper than a cat). Well I put that new fuel pump in and I have put about 1500 miles on her with no more problems so far. Even took care of alot of problems it was having with hesitation and such. I want to thank all of the wonderful people here for saving me so much money as the dealership swore up and down that it was a bad computer. Anyways still crossing my fingers but I'm pretty sure my problem is fixed and wanted to thank you all!!! Really got to reap the rewards as it hit 90 today which is pretty good for Maine, ran like a top all the way to the beach and back. Thanks again everybody.