My 2001 i30 lately after I warm it up and put it in drive orreverse the rpms are around between 500-600 and after I press the gas a little it and go down the road itgoes back to normal. Why do they drop so low after me warming up the car? I used to have a system in but I took it out. Does that have anything to do with it? Could it be voltage regulator?

That is normal. The cold idle is higher than normal to warm up the engine more quickly and probably to bump oil pressure a bit to get things circulating.

+1
Mine is always at around 1000 rps while cold and around 600-700 when warmed up

Yes I do get you on that. My car is the same. idles 6-700 when warmed but what I'm talking about is. When car is warmed in park. When I take I out of park the idle goes to 500 which is unheard of for our vehicles. When I press on the gas goo push off or go down the drive way an press the brake i drive or reverse. It is back to normal. This is very weird. It never did this ever and I have owned this car from 15k to now.

Are you putting teh car into 1st gear, drive, or reverse when this happens?

Either or. When I take it out of park wether it be any gear ,drive or reverse. Neutral it revs same as if it were in park. I have no idea what it could be.

idle is supposed to drop when putting the transmission from neutral or park into gear. you have nothing to worry about.

Yes I know that it is normal for it to drop. But it just never dropped that low previously ever. It would only drop to 6 never any lower.

Try adjusting the base idle via IACV screw. It should be around 550 rpm IIRC.

yea I think maybe I will check that.Where would I find it?

I'm feeling generous... THis is a little more work than the method used on the A32 but the idea is the same:

Idle Air Volume Learning Procedure for 2K-2K1 withOUT Consult-II Tool

Quote:
DESCRIPTION:
“Idle Air Volume Learning” is an operation to learn the idle air volume
that keeps each engine within the specific range. It must be
performed under any of the following conditions:
--Each time IACV-AAC valve, throttle body or ECM is replaced.
--Idle speed or ignition timing is out of specification.

!!!!PRE-CONDITIONING MUST BE DONE 100%!!!!
Before performing “Idle Air Volume Learning”, make sure that all of the following conditions are satisfied. Learning will be cancelled if any of the following conditions are missed for even a moment.
--Battery voltage: More than 12.9V (At idle)
--Engine coolant temperature: 70 - 99°C (158 - 210°F)
--PNP switch: ON <~~~~~IN PARK
--Electric load switch: OFF
(Air conditioner, headlamp, rear window defogger)
On vehicles equipped with daytime light systems, set lighting switch to the 1st position to light only small lamps.
--Cooling fan motor: Not operating
--Steering wheel: Neutral (Straight-ahead position)
--Vehicle speed: Stopped
--Transmission: Warmed-up
For A/T models withOUT CONSULT-II and M/T models, drive
vehicle for 10 minutes.
!!!!PRE-CONDITIONING MUST BE DONE 100%!!!!

OPERATION PROCEDURE WithOUT CONSULT-II
1. Turn ignition switch “ON” and wait at least 1 second.
2. Turn ignition switch “OFF” and wait at least 10 seconds.
3. Start engine and warm it up to normal operating temperature.
4. Check that all items listed under the topic “PRE-CONDITIONING”
(previously mentioned) are in good order.
5. Turn ignition switch “OFF” and wait at least 10 seconds.
6. Start the engine and let it idle for at least 30 seconds.
7. Disconnect throttle position sensor harness connector (brown),
then reconnect it within 5 seconds.
8. Wait 20 seconds.
9. Make sure that idle speed is within specifications. If not, the result will be incomplete. In this case, find the cause of the problem by referring to the NOTE below.
10. Rev up the engine two or three times. Make sure that idle speed and ignition timing are within specifications.

ITEM SPECIFICATION
Idle speed M/T: 625±50 rpm
A/T: 700±50 rpm (in “P” or “N” position)
Ignition timing M/T: 15°±5° BTDC
A/T: 15°±5° BTDC (in “P” or “N” position)

NOTE:
If idle air volume learning cannot be performed successfully, proceed as follows:
1) Check that throttle valve is fully closed.
2) Check PCV valve operation.
3) Check that downstream of throttle valve is free from air leakage.
4) Adjust closed throttle position switch and reset memory.
(Refer to Basic Inspection, EC-111.)
5) When the above three items check out OK, engine component parts and their installation condition are questionable. Check and eliminate the cause of the problem.
It is useful to perform “TROUBLE DIAGNOSIS — SPECIFICATION
VALUE”, EC-143.
6) If any of the following conditions occur after the engine
has started, eliminate the cause of the problem and perform
“Idle air volume learning” all over again:
--Engine stalls.
--Erroneous idle.
--Blown fuses related to the IACV-AAC valve system.