HELP! Engine just starts back-firing at 4000rpm's
 

I'm having a problem where at 4000 rpm's my car just starts hesitating then back firing. I heard from one person that it might be my spark-plugs since my car has been running extremely rich for awhile. I just got it reflashed, new fuel pump, Hallman boost controler (21psi). I already had 3' all the way back, no cat or muffler. Buscher FMIC w/shorter intercooler piping, Turbonetic's BOV (set to recirculating, but does make atmospheric noise) and a Buscher intake. Please let me know if anyone has idea's or know's what's going on. :confused:

The backfiring could be many things.
I see you have no cat or muffler, the car will definetly backfire without these items.
But the hesitation is not cool. Could be ignition related, pull the plugs out and see how they look. More importantly it could be to much fuel or morelikely you could be leaning out. Do you have an egt in the car or wideband? These would be some nice diagnosis tools to see what your a/f is at? Also are you sure your not overboosting thus causing a lean condition? could be so many things really. But if its hesitating stop boosting it and take it somewhere to get checked out!

to eliminate the obvious first, spark plug change! they probably went foul.

Thanks, I was going to try that today
I was told to use BPR70S plugs, anyone can agree or disagree

Did this just happen after you installed the fuel pump.....if so it could be that you forgot to take off the white ring from the oem pump and put in on the walboro. The same thing happened to me and that was the problem.

thats prolly the problem ;)

Thanks, I don't really know since I didn't instal. How can I look to see if this is done. Is there a how to on this forum to show hoe to replace and see if it was done or what it should look like or some way for me to know?

Hey Trskit, you have a pm.

To start pull the negative terminal off the battery
First what you need to do is remove the bottom of the back seats. They are held in by two pull latches on either side of the seat bottom
Second you will see a metal cover on the driver’s side take the four or five screws out and remove
Third you will see a harness plug and fuel line adapters unplug them all
Fourth take all of the screws holding the fuel pump in the tank. (This will take some ingenuity on your part to get at two or three of them)
Next remove the fuel pump (This is a round peg through a square hole type affair and will take some negotiation just don’t be rough)
Lastly lift the fuel pump and look for a white cylindrical hard plastic ring over the motor of the pump. If that is not there you will have issues

There are plenty of write ups on the board in more detail if you hunt them down if not I am sure anyone here including myself can walk you through in more detail

Thanks, nrcooled and Ryno. I'll try this latter today and see if the ring is there. I still have the stock one in the trunk so I'll check to see if teh ring is still on. Thanks for the write-up and I'll let you know how it goes.

i had similair problem and it was very frustrating.....checked everything and couldnt find the problem....
turned out to be my boost controller.....maybe check that....keep turning boost down and see what happens.

Ok I had the same type problem and it was plugs, I had coolent in the sparkplug wells. Check for that before pulling the plugs. I will check this thread offen to find out what happend to yours.

Changed plugs last night and they were shot, but didn't fix problem, also checked the old pump and the ring wasn't on it and talked to shop and he knows he put it on since he has done a bunch and knows about the ring, but said if I show up he'll take apart and show me.

is it backfire or cutting. it could be that you are overboosting hence getting fuel cuts...i think its around 1.5bar 22psi.

check the actuator is not goosed or try turning the boost down see if that cures it

I don't think it's overboosting since I did put it down to about 16 and it was still doing it (not as bad), plus with the new waste gate, boost controler and modifications to the turbo to make it able to achieve higher boost we were running 25 fine before, but were seeing boost creep with the crappy Turbo XS boost controler causing it to spike to 30 psi, plus it was extremely out of tune. It stopped working fine after I installed the new fuel pump (Walbro 255), Hallman boost controler, and DynoFlash Fireball 3 ecu reflash, so it's something with one of these. I'm not sure if it's fuel cut, but it is back firing and anyone behind me thinks that a shot-gun is going off.