Fabspeed airbox and check engine light revisited

Some time ago there were some posting regarding the check engine light (CEL) going on when peopleinstalled the Fabspeed airbox. It seems to be a common problem. My CEL came on immediately after I installed the Fabspeed airbox, exhuast, and a TRG Unichip. I reset it one but it came back on within a day or so. I have read about O2 sensors and MAF sensors being damaged causing this but there was no conclusion. Will the airbox trigger a failure on a sensor that may be going out? Can the MAF sensor get dirty or damaged easily? Will improper ECU mapping cause this? I need some help.

dima, call tony at the racer's group since you have his chip...their piggyback usually works by altering of the timing signals that go into the stock motronic which fool the computer into changing timing and mapping. He will need to get into the air/fuel mixture and correct that in the computer as my friend had that problem. If you are close by to sonoma, you can do a test drive with him and he would have his laptop connected to the piggyback while you drive and do fuel mapping on the spot. this must be more prone to happening on 99's vs. 2000's because i transfered all my mods to my friend's 99 and that happened. On my car the check engine wasn't so much a problem. have you also noticed that occationally, when you sprint the car to high rpms, it occationally would choke?

Dima, did you change the air filter when you installed your Fabspeed airbox? I installed the Fabspeed exhaust and airbox at the same time several months ago. So far no CEL problems. I also replaced the stock air filter with a K&N filter. I used a paper towel to soak up all the oil on the K&N filter before installing. I've heard that the oil on the K&N can sometimes foul things up and cause the CEL to go on.

Hey Ruey, why does it say that you have turbo suspension on a c2? the brake conversion I can believe although I have been told that just by replacing the calipers and maybe the master cylinder, that it will still not perform as well as the turbo because of abs and proportioning valve junk etc. what all do you have in terms of bolt ons and what do you think you gained hp wise? thanks.

Thanks for all the input. I did change the air filter also. I suspect that the problem is either a dirty/damaged MAF that may have happened when box/filter was changed, or there is something wrong with chip mapping. Good idea to call TRG. Also in response to " have you also noticed that occationally, when you sprint the car to high rpms, it occationally would choke?" I do have some choking at high end, especially when I am not full throttle. If I throttle back slightly in a corner or in traffic while at high RPM, I feel some tugs. It's almost like the car is retarding the timing against pinging. I assumed this is part of this overall problem.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> why does it say that you have turbo suspension on a c2? the brake conversion I can believe although I have been told that just by replacing the calipers and maybe the master cylinder, that it will still not perform as well as the turbo because of abs and proportioning valve junk etc. what all do you have in terms of bolt ons and what do you think you gained hp wise? thanks. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">The turbo calipers require either GT3 or turbo wheel spindles, which I was able to get the wheel spindles from someone else much easier as GT3's were not available from the dealer. In the process, the turbo wheel carriers have thicker suspension struts. They actually work fine because I still have C2 springs in there, which are the same size but different spring rates. To the suspension, it ends up being similar to a billstein sport valved shock for a C2 because naturally the Turbo is stiffer than the stock carrera C2. They are also Billstein sports OEM for the turbo which explains why billstein does not make upgradable struts for the 996TT. And in reference if the brakes will not work as good as if on the turbo, I cannot verify if that is true or not as I never made comparisons to the turbo, however, I did place steel brake lines and have the stock ABS timing gears which have a different size as C2's in there so I think it should still be close or maybe even better. My car being close to 400lbs lighter (partially gutted interior GT3 seats, etc.) than a turbo will also have added benefit to better stopping even if the brakes were not performing 100% to their potential. The car does stop much better than the stock and have absolutely no fade on even hard street driving. Prior in stock setup, they did fade occationally. I probably need to track it to test fade threshold. Regarding my bolt ons, I took them all off and basically gave them to my friend in the story I mentioned to Dima. he got my fabspeed exhaust, headers, intake, and chip. I dynoed about 34hp's when I had everything installed. I took them off because I was about to sell the car to upgrade for a turbo, but when i found the resale was too low for my car which I paid in full when I took delivery, I realized the loss was too much of a waste, and decided I'll probably just turbo it later on. Dima, If you have the chocking, then probably 100% you have the same problem he ran into...the fuel distribution is too little for the extra air coming in causing it to choke like an old carburator car getting flooded with gas but the opposite. From what I heard, the car as it approaches high RPM, the fuel number is something like 6, and he had to put it up as high as 9, meaning only 1/2 the correct amount of fuel is being pumped by the injectors. I am not so technical on how the motronics work, but I am led to believe it is definately a fuel/air mixture problem.

Ruey, Much thanks for the info. I will post a report once I get it sorted out. Dima