I lost to stock Corisca in my 82 z28 CFI.

I have no freaking clue what is up, my car has been running badly the last week. It backfired up in the tbi like 4 times today and I am really getting upset.

In a couple months after i take this POS 3 speed out of it, and put in a 5 speed, ill convert to carb, but until then i gotta live with this crap!!!

Any hints to make this thing move just a little bit faster, any help would be greatly appreciated.

Do you have any idea what is causing the back fires. You car will probably run faster if you get the things fixed that are not working properly. Carb/TBI/TPI/MPFI does matter if the car is out of tune or has other problems.

That is the problem, i do not know why it is backfiring like it is, has anyone had this problem before, and what did you do to fix it.

I really do not have the money right now to do a complete tuneup. So if i could just replace one thing, that'd be great.

What is your fuel presure? Back firing through the intake is an indication of a lean situation. I'd put money on a bad fuel pump, but check your fuel filter too.

The fuel pump that came in those cars (CFI) are junk, right from the factory. I couldn't raise more than 10 PSI w/my old FP, even with an adjustable FPR! I installed a 255 LPH pump, and dropped a second in the 1/4! LOL.

AFTER you've checked the fuel delivery, THEN move on to vacuum leaks, and THEN balance the two throttle bodies.

Your car should be running high 14's which will not only destroy a Corsica, but run better than most 305 TPI cars. If you look at my sig, you can see that the CFI system will work fine when set up properly. Also I have a friend w/an 84 CFI Vette. 130,000 miles. His mods include a converter, and a ported intake. That is all. With a stock auto trans the tired old vette runs 14.6's at 4500 feet elevation! Not bad IMO.

Hey, I am going to check that fuel filter tomorrow, dont fuel pumps usually just go out if they're bad. I havent really heard of one just getting weak.. hmmm but I'm not a mechanic so thats why I am asking you.

Also, high 14's, if I could pull a high 14 in this thing, i would jump up in the air and scream for an hour straight. I just dont think it is possible. Are there any tweaks that you know of that i can perform?

I think I'll reach mid-low 14's once I convert to carb, but I doubt i can do even close to that with a stock CFI unit.

Btw my car is a 82 CFI Z28 with 116k miles on the clock ( which isnt much for such an old car )

One more thing, I think you are right, it is fuel related, because when i floor it, thats the only time it backfires, which means its not getting enough of something, which probably is fuel. Thanks.

Check the timing, firing order, the condition of the spark plugs, wires cap rotor and see if there is any codes stored in the puter.

That should get ya some results.

Kat

That's what happend to mine. MOST of the time, fuel pumps just crap out, but in my case the car ran fine. Then one day I went to the track and ran horrible and very inconsistent times. I didn't even know there was a problem until I measured the performance. Once I replaced the pump and set the presure, it ran the number I thought it should.
When my car had the original 305, I installed a 5 speed like you want to do, installed edelbrock headers, 160* thermostat, raised the fuel presure slightly, advanced the timing, and chucked the clutch-fan in favor of an electric. Basically I did headers, tune, and "free mods". Everthing else stock, it ran a 14.5 @ 95mph at Epping NH. You can definitely break 14's with an un-modded crossfire intake. BTW swapping to a carb will not put you in the 14's! Not unless you loose the stock exhaust from the heads to the tail pipe, and ditch that three speed, at which point, as I have just explained, you can have the CFI in the 14's and still enjoy pump/choke-free cold starts and 24+ mpg.

You're right, it's not getting enough fuel at WOT. Get that fuel delivery working properly and I'm sure you'll be pleasnatly surprized at what the CFI does.

Alright, sounds good, but when I convert to carb, I forgot to say, but I am adding a few things while doing this. Main things will be better intake, cam, and a bad *** carb.

24+ MPG, I wish i could ge 10+ MPG. I get horrible gas mileage, and I have no clue what it is. Maybe my car is in need of a tuneup (it will be getting most of it, next week sometime) so I am not to worried about that.

Also, if my fuel pump is working just fine, and I upgraded to another fuel pump, would I see any gains, or was your's just crapping out on you?

Thanks for the help.

My fuel pump was crapping on me. That is why I saw the gains-the old one couldn't deliver what the engine needed.

I have had three engines in my car over the last 10 years... all fed by the same CFI system. I have gotten NO LESS than 24 mpg (highway) with any of the engines, including my current 300+ hp sb400 that I have now. If you are getting less than 20 mpg (which you are) then something is very wrong (which something is). I still think you will BARELY break 14's with your propsed mods. Do the exhaust FIRST. That is by FAR, the worst part on your car. Please;
1. Get the engine functioning correctly -fuel, ignition, timing, balanced TB's, temp.
2. headers, headers, headers!!
3. cat back
4."power tune" Optimize your timing, and fuel presure for your mods.
5. 5-speed

These steps will put you SOLIDLY in the 14's and give you an efficient running car to boot. Your cam isn't bad, it's the same as the 305 HO (L69) cam. You will see far bigger gains going after the exhaust than spending money on a cam (at this point).

If you slap on a "bad ***"carb (whatever THAT is), intake, and cam. you will have a high 14 second car that gets 15-20 mpg when tuned correctly. I'm telling you how to get a MID 14 second, 24 mpg car.

Well, I am not the most mechanically inclined person on these boards. But I do have a friend who is hehe ( well not on these boards, but he knows just about everything when it comes to cars ). He is helping me tweak this thing next weak (tuneup, emissions junk taken off, and any other tweaks that can be done) we will be doing then. Also, its not all about speed for me, I would much rather have a more fun car (5 speed) then a fast boring car (automatic). Also my car needs paint (which I am holding off on until next spring, so performance comes before that hehe).

My plans-

Next Week - Tune up (kind of)

Next 2-3 Weeks - 5 speed conversion (Saving as we speak)

Next 2-3 Months - Convert to carb, Headers, Exhaust, Cam, Intake, and whatever other performance parts I can find at the time.

Bad *** carb = I forget exactly what it was but its like a 650 cfm dp or something.

Also you said that I have a high 14 second car, hehe, if i do all these mods to it and still have a high 14 second car, that does not make sense. I think maybe you meant stock we have high 15 Second cars, which is true.

Thanks for your help, very appreciative.

any updates

My CFI does the same thing.Is it the fuel pump

He must still be looking for his gas mileage