2000 i30t

i noticed something wierd or different yesterday while making a long trip. at speeds of about 80 or 85, when i let off the gas to coast without braking, the rpm went from 4k to 3k normally and then from 3k it fell rapidly and abnormally it seems, to 1k. so im at 1k rpms while coasting at speeds of 75 or 80. then to pick up speed after coasting, there was a slight delay between me pressing gas pedal and my speed increasing as the rpm went back up. im also noticing this around the city in normal traffic. if i pick up speed to about 40 and let off gas to coast, i can feel the car drop rpm rapidly and to pick up speed after coasting theres a delay (not so much as with higher speeds but there is a delay). from a dead stop, everything seems normal through each gear, from what i can tell.
let me know what you guys think or if you need more info. thanks.

How many miles?

Maybe one of the emmision sensors, ie o2, or MAF...but that's just a wild guess.
Chucky.

If it is same as when you are coming to a stop, say cruising at 3000rpm going 60MPH, then brake and around 10-20MPH the rpms drop to ~700 then back to ~1100 and back to idle at complete stop, then normal.

as a matter of fact, just hit 170k...and also, car was just inspected this month so any code would have showed up during that i am guessing.

actually, i am idling at 1k or slightly below.

im having somewhat of the same problem but in my suzuki aerio, while coasting the rpm would suddenly drop then pickup like you said, same as when i hit the accel. it would hesitate before picking up speed. also when i come to a complete stop and try to get moving again the car would cut off if i just step on the accel. so i must try to tap it slowly 1-2 times before it picks up. i was told that it could be the fuel filter but im yet to change that so yea i have no idea what else the problem can be.

I used to have a pathfinder with 150k miles on it. It turned out that the fuel filter went bad and in turn clogged my fuel injectors. I ran out and baught a new fuel filter and some good ol fuel injecotr cleaner. and Shazaam my baby was good as new. plus at that mileage it wouldnt hurt to do both anyway. On top of that i would suggest using a premium fuel. lay off the regular and give that sucker some premium (93) gas. for higher mileage cars it really makes a diffrence. oh and the o2 sensor is a possibility however i dont think thats it. just my $0.02

sounds like a bad MAF...

thanks guys...i will look into the fuel filter and MAF.

A guy I work with has an 01 I-30...as he described it, he told me he thought his transmission was "slipping". He took it to the dealer and they ended up replacing an O2 sensor...fixed the problem. He said the Check Engine light never came on. So your problem could very well be something that simple.

thanks. i tried searching for write-ups on cleaning the MAF but i'm gonna go outside and see what i can see. i will check into the o2 sensors also.

hey.. it just might be the fact that the torque converter is letting loose because your foot is off the accelerator and the tps is not sending voltage to the tcm to build fluid pressure in the tranny, this is done so there will be less load on the tranny during coasting...mine does the same thing....thats just what i understand.....