I bought my car about a year ago which needed a real good tuning due to the fact that the first owner had just installed a CAM,LONG TUBE HOOKER HEADERS,LS6 INTAKE,LS6 HEADS, 29LB Injectors MAF & throttle off a Z06 and a TCI 3500 Stall. They tuned it and said it had very bad backfiring once it reaches 5000rpm and didn’t know exactly what was causing it but they got the car running pretty good besides that. It only happens when I floor it but NOT when I drive slowly up to 5000rpm. It back fires and then shuts off and I have to pull over and turn it on again also I only get about 110 miles before I have to refuel. Any Ideas??

 

Anyone Any Guesses??

 

110 miles before you have to refuel? Sounds to me like you are having WAY too much fuel under WOT... Whats your A/f? Whats your fuel pressure?

 

is it setting any codes? Sounds like exactly what I had when my thrust bearing was so worn out that the CPS signal was lost due to the crank reluctor walking away from the cranp osition sensor.

Check your CPS and crank endplay.

*edit* just noticed you are having bad gas milage as well. Could be all tune related. But again...are you having any codes? SES light on?

 

One of the first things to check when backfiring is your plug wires. Check the connection of the boots or use it as an excuse to upgrade to aftermarket to see if that helps. After that I'd look into your tuning.

What year is the car? 29 lb (28.8lb specifically) is the stock injector size of 01/02 model f-bodys so I don't know why the guy would install an already stock option injector.

 

backfiring can be caused by a vaccum leak also . . . or a clogged fuel filter. i'm with brian, why would he install stock injectors with a bigger cam, heads and headers?

 

It's a 98 and the check engine light comes up every now and then. I just had MSd wires put in last week and same crap. as for the injectors I have no Idea why he did that.

 

Any other guesses??

 

haha,sounds like what they might have done is upped the fuel pressure to try and compensate for the lack of fuel from the smaller injectors. i would say for a cam you should atleast go up to 36# injectors ( but it also depends on the cam) and when it gets up high its getting tons of fuel and back pressure to the injectors and may be causing them to just, leak.....lol, im not saying this is what is wrong...but i have heard of this.....leaky injectors from high fuel pressure anyways

 

Thats good to know. I'll talk to my mechanic about that one.