2g gst backfires at 4500 or when boost starts

[boosted954g63]

I have a 95 gst and when ever I rev the engine to around 4500 or when I am driving it when boost starts it backfires and stutters. I just did a boost leak test with soapy water and I found a couple and fixed them but it still does it. I am thinking it could be ignition or fuel. O and I just replced the fuel filter and it still does it. Any other segestions?? Thanks in advanced.

 

[972ndgen]

did you check all the weird spots like injector seals, throttle body gasket, BOV gasket. Because I'm sure that you're boostin by 4500. i know we just fixed alot of leaks in my friends 4g and it was doing the same thing at the same time. run good now.

 

[boosted954g63]

Yes I did the throttle body and injectors was the first place I checked. The BISS screw was leaking but I fixed that. I checked the BOV and it had a little leak and I fixed that too. Yea I know that it should be hitting boost around 3k, which is about the time it starts backfiring when driving it. O yea I forgot to mention, when I was revin it up and hit when it backfires, it would shoot flames out the exhaust.

 

[BoostFrenzy]

I'd check the ignition then. Could be some fouled plugs or bad wiring. Once you check them, make sure you have all the connections right and firmly in place.

 

[boosted954g63]

I just replaced the wires to see if it would fix it and it did not change. Spark plugs are not too old but I will check them when I get time. O I know that they are gapped to .028.

 

[BoostFrenzy]

Its not a matter of how old they are, but how they have faired over that period of time. If you run rich for too long, they go bad. You over heat them, they go bad.

http://dirtbike.off-road.com/dirtbike/data/articlestandard/dirtbike/232006/332655/4.jpg
This is and example of what they would look like for certain situations.

Not only look at the tips, but also the threads at the tip of it. Because if there is oil on it then that is a more serious problem.

http://www.dsmtuners.com/forums/showthread.php?t=215785&highlight=spark+plug+threads
(Last post by the Wiseman)

 

[boosted954g63]

Alright I will take a look at them again when I have time.

 

[blacklabel5281]

Hey bro. I have the same problem I think. I'll get into it and it sounds like a popping sound? Then you get full power for a few seconds then it pops again. Mine does it in the top end of first and midway through third. My bud was telling me I was shooting foot flames out my exhaust.

 

[boosted954g63]

Yea that sounds like I but mine does it in any gear and when I am rev'in it up. Any other idea??? Thats for the help so far.

 

[BoostFrenzy]

Are you sure you just aren't running pig rich? Or hitting fuel cut? I checked your profile and it doesn't show any type of tuning or logging device. If you don't have them, get them. And also gauges if you don't have those. If you do have any of those, could you watch what they do when it backfires please. Would be very good info to have.

 

[boosted954g63]

Well I have a boost gauge hooked up and I also have a A/F gauge but that is not hooked up. No I do not have a logger, I have been tring to find one cheap but I have not found any locally. I am right now seeing how to hook up the A/F guage. And with the boost when it backfires it does not matter if there is any boost when it hits around 4500 it still backfires.

 

[viprez586]

dont forget some common culprit of boost leaks are the compressor housing and the elbow, Meet RTV your new best friend for boost leaks.
Quick diagnosis of running rich, have your friend rev your engine while you watch the exhaust. Blue=Oil, White=Coolant, Black=Fuel
If your A/F gauge is the one that taps into the O2 sensor they aren't very accurate. Invest into a wideband, aside from being accurate they make tuning easy peasy.

 

[BoostFrenzy]

Or hitting boost cut?

Sorry boys, i meant fuel cut. Sorry for the mistake. I'll change it

 

[blacklabel5281]

I can tell you what it is. Its your Ignition Coil. Mine was arking which made it not run smooth. So you might wanna have that checked.

 

[chetvram]

Does your missfire get worse as you add more throttle? Try running through the power band at low throttle than at high and compare. If you have a boost leak it should get worse with more throttle if it doesn';t change than most likely you have some kind of ignition issue