Slight Exhaust Sputtering When Idling

[satanic]

Hey all,

Ever since getting my cat back put on I've noticed that there is some strange sputtering that occurs when I have the car in PARK or idle. The car is an R34 GTT Auto and the system is a cat back TRUST.

The sputtering is ever so slight, but noticeable. The idling seems to hold for three seconds then have 2-3 small sputters then hold again. Almost like a "PUT PUT.... PUT PUT PUT.... PUT PUT"

Any help guys? I've already resetted the ECU to relearn the dynamics with the exhaust. Could it be something that's about to give up?

YOUR HELP IS MUCH APPRECIATED!!!

[d00dz]

Check sparks or coils... ?

[satanic]

Yeah I've got a new set or Iridiums waiting to be put in... but it the small puttering noise a normal thing with aftermarket exahusts? Or is it supposed to be a constant uninteruppted note?

[J_R32]

this is normal, as long as your revs dont drop excessively, this slight misfires, occurs in nearly all 6 cyclinder engines.it is cause by the "uneven" firing sequence of each of the cyclinders, because not all cyclinders are going up and down at the same time. (basically 2 cyclinders are at the "top", 2 at the "bottom" of the cycle, and the other 2 in the "middle" of the combustions cycle. sorry for crude explaination, maybe someone can explain it better.

and because you have a larger diameter exhaust, this slight mis fire sputter noise just got "amplified" thru a louder exhaust, on a stock exhaust you cant hear it.

[rd-runr]

I never had sputtering coming from my 3' exhaust when it was put on. Not even now.

[satanic]

Thanks for all the help guys... here's an update, might be the reason for it all.

I've noticed that on flat surfaces the puttering is non existent and it is all smooth. However, when I go up my driveway which is like 45 degrees, that is when it happens.

Could this be simply due to the fuel delivery or the fuel sensors affected due to the angle?

Thanks guys for your help in this!