Help from the tech gods needed!!

[240sx2soon]

Maybe just a silly nilly question or some basic maintnance stuff I'm missing but my car seems to be running really rough since I installed the header exhaust high flow cat and intake. There is alot of backfiring when I let off the throttle ( which from what I understand is pretty normal for 3" pipe on an N/A motor ) but it almost sounds like detonation at part throttle while I'm doing 50 or 60 mph. If I put it in neutral the popping sound stops and there is no more harsh running even if I rev it which leads me to belive it's some type of rubbing or vibration from the transmission. I have been running 93 since I put the parts on and I have already run a bottle of injecter cleaner through a few thousand miles ago. I have a can of seafoam in the house that I have been planning on running through but just haven't gotten to it yet. Another stange thing I am seeing is that when I rev the engine ( just sitting idle in the driveway, GF ws backing it out and I noticed it ) there are what looks like super fine metal particles coming out in a mist. There is a small build up of these particles on the bumper above the exit of the exhaust and if you look at it in the sun you can see the light glinting off of the particles in the air. I am thinking it's just the new converter or somthing that was in the exhaust or header thats just slowly eliminating itself as things settle in but Im not sure. Any help would be appreciated thanks guys, hope my sh*t isn't jacked up to bad

[Fenvy]

it's going to go kaaaa-booooooooooom

sorry, just messing around, it's 5am and I am still working on my english papaer

[SlowBack]

Sounds to me like a nice running KA motor.

[240sx2soon]

Apparantly these to gods are split , would any other gods like to offer an opinion?

[ShionS14]

i wouldnt call myself a god but i would suggest first to pull your plugs and look at them, if they are white and deteriating then you are running lean and if they are black and gunked up you are running rich. if your car is obdII you have to remember that the second o2 sensor needs to be behind the cat. the second o2 basically determines if your ecu will run an open or closed loop fuel setup. secondly, what octane did you run before? switching octanes can play with the cars ecu, which it doesnt like to be toyed with. finally the cat holds a lot of heat along with the header pipe if its ceramic coated and any excess fuel that isnt burned during combustion will actually ignite with a flame front on the verge of detonation which is why you here the poppong in exhaust system. i personally have an aem intake hotshot header, no cat except that hollow secondary dumby cat that nissan puts in and greddy sp exhaust. my secondary o2 is disconnected which throws an engine code but runs just fine and it has a nice little gurgling pop when ever i down shift. as for as the glittery crap coming out of your exhaust you got me beat, maybe its fairy dust?

[eddiec]

i almost have the same set-up: hotshot, no cat, small muffler. i get a backfire when i lift off throttle. but no continuous popping or anything. i'd check the plugs like ^^they said. and if your car is obdii, hook a scan tool up if you have access to one.

[240sx2soon]

I don't switch octane to often, it's usually 93 but every now and again I'll go back to 89 for a tank. The secondary O2 sensor is reading dirty stuff before it gets to my cat, should I run an O2 simulator to trick it into thinking things are hunky dory? The plugs may be something I do after work, simple easy and hopefully the problem, I had planned to get a timing gun and advance the timing a bit but I think I'll address the other things before farting around with that.

[ShionS14]

actually your best bet would be to go to a shop and weld a bung behind the cat and plug up the original, that way you dont have to lye to the computer it will be set up the way the computer likes

[240sx2soon]

Let me guess your occupation....emisions officer? JKI have a close friend who makes simulators for spec V's and wants to start doing them for 240's soI'll probablly be the test bed for his part. I changed the spark plugs last night to Bosch dual platinum and things seem to have gotten alittle better but I was also reminded that I have a small exhaust leak directly under the drivers seat where the header flange meets the cat ( header flange=2 1/2" + cat flange=3" = exhaust leak ) that may be causing some of my issues as well. I'l have to make another trip to the parts store to see if they have a solid 2 1/2" gasket thats not universal cause the slots that are in the universal reach all the way to the opening on the cat and cause it to leak. silly human

[manama240]

If you have a leak that close to the engine you will have some issues. when you let off the gas i'm assuming you are sucking cold air back in through that hole. That also could be messing with your O2 sensor. Fix the leak first then see what happens.

[ShionS14]

ya definately fix that leak and let us know

[240sx2soon]

More silly human tricks, I forgot to plug in the secondary O2 sensor after installing everything DOH!!! I did get under the car last night and fix the exhaust leak, perhaps only for a little while, by using the old 2 1/2" ID gasket and RTV ing it to the 3" ID gasket and putting it in place. There was a small puff ( I mean barely noticable ) after that so I packed a little more RTV on it until I can get another 2 1?2" gasket ( you see the old one burned off all the material where the leak was so it wasn't a very good gasket ). It's seems to be a little more responsive since doing that and the plugs. I'm gonna run the seafoam thing through this weekend and see what else it will accomplish. that is all.....

[manama240]

DOh! well order yourself a copper or aluminum gasket. I hope you plugged the O2 sensor hole properly. Since it's more reponsive that should have been your problem.

[240sx2soon]

I didn't actually plug the O2 sensor hole I just plugged the weather pack attached to the end of the sensor back in. I had to remove it to get the old exhaust off. I need to source out a proper gasket for it but in the mean time this etup should work fine. I have to get the front end back up on ramps and finish my ground wire install though, I still haven't gotten to the alternator wire.

[ShionS14]

after you run the seafoam it would be a very good idea to change your plugs, the increased heat will burn up the electrode tower pretty quickly, or better yet if you still have your old plugs put them in before you do the seafoam. as for the exhaust, you still need to plug up the secondary o2 bung on your header

[240sx2soon]

If I plug it what will I use to keep the CEL from going off?

[ShionS14]

with the second o2 sensor not hooked up your check engine light should have already gone off. in order for it to work you have to hook up the second o2 behind the catalytic converter