'98 i30 - trying to tune out a stutter at idle

After cleaning the TB/IACV/EGRGuide with new fuel filter/plugs/PCV AND putting it back together right - everything runs really smooth EXCEPT there is a momentary, intermittent stutter at idle.

RPMs dip maybe 25 revolutions total - and then it's right back to idling its happy little a** off. Happens in Drive or Park/Neutral. Not consistent re: frequency and haven't tallied it with a stopwatch (yet) - but the drops in RPM are timed far enough apart (and there's no symptoms when you've got your foot on the gas) that you start to forget that it happened - until it happens again, the next time you come to a stoplight.

Have gotten a single P1440 code since putting it back on the road - this was during a rare 30+ minute freeway drive, as this car is typically not operated for more than 25 minutes at a stretch on mostly city streets. I re-tightened the gas cap (I was actually the one that filled it up last, its not my usual car, and I may very well have only tightened gas cap one click at that time) and then cleared the code - code has not returned and no other codes, but the intermittent stutter at idle is still present. Not sure whether an EVAP code will trip with only short duration operation.

This post from IlyaK describes the same thing - I think he sold his 4thGen though:

https://maxima.org/forums/4th-genera...569-p1440.html

I've still not been able to find any indicated leak in the EVAP system. There are lots of threads from rustbelt forum users about corrosion in the evap charcoal canister, and the plunger/solenoid at the top of the can sticking...but there is no rust here in Houston at all, and it seems most likely that I dislodged some EVAP hose/otherwise F'd it up when I was working in the engine room last rather than some new issue at the a** end of the car.

Don't think a bad coil is suddenly causing a miss - there would be other symptoms/codes too if that were the case.

Can anyone suggest a cause for this stutter other than "leak in EVAP system"?

This seems like exactly when using a smoke machine would save a lot of time. I see professional tools that cost $700. I also see this:


and I was going to post about DJ smoke machines, but then I see this:

http://www.ebay.com/itm/EVAP-Smoke-M...-/301673812635

$700+ is too much to spend for one- or two-time use - and my project is to fix the 4thGen, not build smoke machines. Building smoke machines appears to be all this Ebay seller does...the term "product liability" comes to mind, but he's apparently selling quite a few of them, and I don't recall hearing about any of them catching on fire (unlike "hoverboards", for example). $100 is a lot of profit to him on a collection of parts and just a little bit of his labor but if I was so tight about it I could damn well drill my own paintcan, right?

What do you think about using a homebrew mineral-oil based smoke machine like this one on the '98 i30? Is that "Standard Service Adaptor" the right part to hook up to the EVAP service port (schrader valve behind a green plastic cap)?

Thanks

 

I had a similar problem. Replaced the plugs with NGKs and it went away.