let me get this straight......
you drive the car in normal mode and the O/D is off.....all of a sudden the engine rpm increases by 1000~1500 rpm and then back to normal again

is this correct?????????????

My idle rpm is 1000. When I step on the accelerator and start to move a couple of meters, it will hard shift (shift shock). When I'm already moving a bit faster 1500 to 2000 rpm, it will suddenly slow down and I can feel the gear shifting (probably to low gear). It will do this for a couple of seconds and then the car will run ok again. I also feel hard shifts when I'm about to make a full stop. I already drained and changed the ATF.

1000 rpm at idle ??????? that is way too high, should be +_750 rpm, someone messed with the engine base settings, who did this??? Can't be a Hyundai techie.
1- loosen the idle switch (undo the 1-wire terminal) at the throttle linkage were the accelerator cable connects to the trottle body; back it out, till there is an airgap between the switch tip and the trottle lever (BTW, check the switch, the terminal makes a connection to ground when the switch tip is pressed in), then turn it in till the trottle starts to open, STOP, from that point turn the switch in (tighten more) 15/16 of a turn (almost one turn) then tighten the lock nut.

let's see what happen now

This post has been edited by duke: Dec 5 2004, 07:27 PM

Idle at drive down to 800 with AC on. Hard shifting and sudden slow down still present. I noticed that it occurs more frequently early morning when I leave for the office. When the engine warms up after more than 30 mins of driving, it occurs less frequently. Hope you can help Duke. Thanks.

When it slows down, its as if its in between gears because when I step on the gas, the engine just revs but no speed. RPM also increases but car still moving slow. The slow down occurs for less than 30 secs.

Have you attempted to shift the car manually, i.e from Low to 2nd to drive?

Does your transmission slip or thump when shifting in this manner?

Ok, now the idle is almost normal (should be +-750 in "N")
Now check the TPS voltage at terminal 3 (green/yellow or can be green/white) with the ingine at idle in "N". The voltage should be +-0.48volt. If not, you can ajust is by loosening the 2 screws, and move the sensor.
Now lets see.

I can still feel hard shifting when in 2. Will try your suggestion asap but I don't know where terminal 3 is and I don't have a voltmeter or device to measure voltage. Will try to borrow though.

Duke, can you point me to where terminal 3 is located? Thanks.

it's the green wire with a yellow stripe