still running lean?

hey-

so here's the deal. I have a 95 n/t which i am having a problem with. A while ago, it started bucking and sputtering when i hit the gas under 2500rpm. i have a manual transmission, and if i put the pedal to the floor at anything less than 2500, it bucks like the fuel is cutting out intermittently or something.... so i couldnt figure out what it was.... What i did was i took a look at the plugs, and the tips were all white. I bought the ngk plugs, gapped them to factory specs, and put them in. the problem ceased instantly.

Now, a few weeks later, its coming back. my dad thinks it is running lean... because the plugs are getting too hot. so i gapped down the plugs a few hundredths, and it seemed to help a little, but the problem is still definately there.

the only performance 'mod' i've done is a cold air intake... I'm not sure what else to do, any input would be greatly appreciated.

thanks.

If the 2g NTs are MAP sensor cars, then a cold air intake could make things leaner. And if you are up north its been pretty cold lately making it worse. The problem is you have nothing available to adjust it richer to see if that helps. No AFC, fuel reg, etc. What I think I would try is to go back to the stock intake if you can and see if there is any difference. My suspicion is that for it to be the cause of your low rpm issue it would have to be damn lean, and I just dont see how thats possible. Modern cars do run quite lean for emissions purpose, and modern combution chamber design lets them get away with it at WOT too. I Think the white plugs and the bucking are unrelated.

I would try to find someone with an OBD2 logger they can plug in. Although the 95 NTs may not have been OBD2. I know the turbo 95s are. Another alternative is to drop 50-70 bucks on a dyno session and use thier wideband O2 sensor. If its lean you'll know for sure. And you'll get some HP numbers to boot.

I have a wideband and logger built in to my car. I can't imagine how I used to trouble shoot these problems without all this gear.. :)

i would try changing the fuel filter. if your filter is started to get clogged then you can start to have fuel supply problems. besides, a filter's like 3 bucks and you should do them as maintenance anyway

thanks for the input, guys.
yes, i will replace the filter, i might as well.

now here's what my dad's telling me... tell me what you think -

he says that it could possibly be a coil going bad or something like that, a problem with the ignition system, and gapping the plugs down to .35 or something might help. because if the ignition system is having trouble arcing the gap, it might cause misfires and such... so i think im going to gap it down 5 hundredths or something like that. any other input?

I have never seen a fuel filter cause any problems aside from at WOT. And think about it, when do you need the most fuel? Certainly not below 2500 rpm. Same for ignition problems. You will typically see ignition problems at high cylinder pressure. Not sure where the Volumetric Efficiency peaks on the 420 though, so it may still be worth looking into. And I would still try the stock intake if possible just to eliminate that as a suspect. Highly unlikely, but it should be easy enough to do.

thanks for all your input... ill let you know how it turns out, ill gap them down a few hundredths for the hell of it, and ill try and put the stock airbox back on. thanks again.