Backfiring at WOT? Need help.
04-18-2005, 04:40 PM
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Backfiring at WOT? Need help. Went to track and first pass was ok, though on the video sounded like engine rpm fluctuated a little a couple of times. Second pass half way though 2nd it backfired and fell on its face and backfired a little more. Now everytime I go WOT it backfires and fall on its face or dies. Then it starts up and runs fine. It only does it at WOT. Ive changed or swapped plugs,TPS, IAT, ITC, MAF, and checked fuel pressure and idle its 60psi and 58 when I rev it under hood. Plugs looked rich like never before. Its like when it goes WOT it dumps too much fuel. I cant tell this with gauge going down the road though. I do have a Walbro 255 pump with the stock regulator. Dont know if the regulator is letting too much fuel by under a load. I get no codes of any kind and car drives under normal conditions fine. Can anyone shed some light. I thought I read a post a while back about problems with stock regulator and high pressur pump. Thanks for any info. Jason
04-18-2005, 09:12 PM
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What would make me go lean all of a sudden? Wish I knew Im at wits end. May have to drop the tank and take a look at the pump. Im only running the stock 26#ers and dynoed 413rwhp and know it was over 80% duty cycle.
04-18-2005, 10:05 PM
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A friend of mine has this EXACT same problem... Part throttle driving is perfect until halfway through WOT then BAM! and the car dies. Right after the backfire the wideband shows waaaay lean but I think it has more to do with the car dying. And after the car dies, its still in gear (A4) and if given any throttle it will continue to backfire. Makes me think the ignition is still firing but no fuel or something...
I hope we can get to the bottom of this...
I hope we can get to the bottom of this...
04-18-2005, 10:38 PM
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Originally Posted by WS6FirebirdTA00
wonder if the injectors could be maxing out. redhardsupra said his maxed out at 5500 with less power i think.
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04-19-2005, 06:19 AM
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The car has always ran fine with the 26#ers. txhorns281, my car does the same thing as your friends. If i try to give it gas after the first nosedive its popping and backfiring like its trying to refire. Im really starting to think the feul pump wiggin out.
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04-19-2005, 06:35 PM
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backfiring at WOT not alone Hey I have a 95 Z28 A4 and am haveing the same problem . Car runs fine at all speeds as lone as I don't get on it with a WOT. If I do around 4500 on up it feels like the rev limiter is shutting down the engine and back fires let off the gas and all is ok. It has plenty of power in the first couple shifts and runs fine as long as I don't go WOT. On the way home from work today is was doing 70 and just to see what would happen I kicked it down to WOT it down shifted ok and took of did'nt go over 4500 rpm as I was over 70 but pulled good.What can be doing this sounds like a couple of us are haveing the same problem. Fuel filter,fuel pressure switch, fuel pressure regulator,opti spark,pcm prob . What is it If three of use are haveing this problem I know somebody out there has had this happen aand knows what the prob is.
Chime in and help us out.
Chime in and help us out.
04-20-2005, 08:02 AM
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No codes, and no idea about fuel pump. I do know my buddy's car used to a nitrous car so there is a good chance of an aftermarket pump. I think he's starting simple with the fuel filter... 
04-20-2005, 08:51 PM
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I found out what was wrong with my car. The computer was going into limp mode, it will do this when it senses something wrong electronicly, grounds e.t.c. So I checked all the grounds and when I got to starter, the crank sensor wires were rubbing the main ground spade right above the starter on the block. It was in a bind due to the dipstick tube. The plastic coating on the crank sensor wires were just starting to get exposed so it would ground out causing the pcm to go limp. Re routed it all and the car runs like a champ now. Hope this helps someone. See ya!
05-06-2005, 03:07 PM
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TTT
In my case, the fuel pressure has been verified 58 psi at the rail, all grounds have been inspected and are isolated from contact and seated well. Still getting backfire then shutdown at mid-WOT
Any other thoughts?
In my case, the fuel pressure has been verified 58 psi at the rail, all grounds have been inspected and are isolated from contact and seated well. Still getting backfire then shutdown at mid-WOT
Any other thoughts?
05-12-2005, 10:21 PM
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same **** here....Ive got the STS turbo kit on my 99 TA. First it started doing what you explained at WOT because of an exhaust leak..got it fixed and it ran real good. Installed 42LB injectors and a walbro 255LPH intank pump, worked fine for 2 weeks... started doing something similar although it started quickly popping and found out it was running lean...hooked a fuel pressure gauge up to it....amazingly running 5psi at the fuel rails...can't believe it, my brand new walbro 255 pump is bad...now Im out to find out why it went bad. Im tossing a new walbro 255 in there hopefully permanently solving the problem. Although Im worried the same thing will happen...the pump was only in for 2 weeks.
05-13-2005, 09:14 AM
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Originally Posted by transamws6r
same **** here....Ive got the STS turbo kit on my 99 TA. First it started doing what you explained at WOT because of an exhaust leak..got it fixed and it ran real good. Installed 42LB injectors and a walbro 255LPH intank pump, worked fine for 2 weeks... started doing something similar although it started quickly popping and found out it was running lean...hooked a fuel pressure gauge up to it....amazingly running 5psi at the fuel rails...can't believe it, my brand new walbro 255 pump is bad...now Im out to find out why it went bad. Im tossing a new walbro 255 in there hopefully permanently solving the problem. Although Im worried the same thing will happen...the pump was only in for 2 weeks.
05-13-2005, 09:22 AM
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It started out being the exhaust leak when you'd be WOT around 4000+ rpms. Now it started out being 3500rpms it would bog out, an eventually 3000 now its a little more than 2000...I ran a pressure gauge on my fuel system to find out it is the pump. I would recommend doing the same if not done. I would definetly say exhaust leaks are a great possibility in your case. The banged up y-pipe would not affect something so severe.
