Hello,

I have an 03 s2k which I had tuned with a Full Race turbo kit with AEM v2 software nearly a year ago. Fast forward to about 2 weeks ago, I took my car to a local track to test it out. Everything was going great until about halfway through the day and I started to get horrible backfire problems. Before this, I would backfire maybe once a week so it wasn't something of concern to me. When I say backfire, I mean that I cannot rev the car past about 4000 rpm because it simply wont; the car backfires without stop and I cannot accelerate. I get a huge poof of black smoke coming out of the exhaust which leads me to believe that it is running too rich, but that would make me think something with the tune changed, although that doesn't seems plausible to me (maybe I'm wrong). Also, this didn't seem like a slowly occurring problem; it was day and night. One second I'm driving fine, the next the car is backfiring uncontrollably.

Since I was at the track, I started to talk to a guy from a local tuning shop who had experience with Hondas. He though it might be the gaping on my plugs so we pulled them and set the gap, but that didn't fix the problem. So next thing I did was head over to a local NAPA and got some NGK iridium heat range 7 plugs and replaced them (I was using 8s before). Still had the same exact problem. So I go and check my compression and I'm running 200-220 on all cylinders, same as before I tuned it.

Honestly at this point I am beyond my mechanical expertise on what to do. I am not very mechanically inclined, and frankly, am afraid of messing something up by trying to fix it myself. I don't mind paying someone to do it for me if they do good work but would like to avoid fixing things that don't need to be fixed. Some other ideas that I've had thrown at me could be the timing is now off but I'm not sure. I've been told the car could also be running too rich. I have an AEM air/fuel digital gauge and under throttle it seems to drop as low at 13.1 when I've been told it should be more around 14.5 so maybe that's the issue.

Another interesting note: the car runs perfectly while idling and normal driving. I get no knocking or shaking of the car. Also, if I only apply about 25% throttle, I can rev right past 4k RPM all the way to about 7k where no matter how lightly I apply throttle it will begin to backfire. I can also build boost up to 4k RPM but once I hit around that mark, its when the problems start. I did use search but didn't find any threads that seemed to apply to my situation so I decided to make my own post.

Any help, ideas, or places you know I could take the car would be greatly appreciated. I live in the Olympia WA area.

Thanks,
Marshall