sometimes wen i start my monte up, it lays all the way back down to half an rpm and when i drive and come to a stop, the lights dim and it seems like its going to choke out.. wen i shift also into reverse or drive .. WHY

 

i have the same problem. THe dimming lights was from an almost dead battery, i had the battery checked and it was super low and wouldnt take a charge. I had a warranty on my battery from checker so i got a brand new one and problem gone. The idle problem is still there for me though. Have no idea what it is

 

Any check engine lights or codes?

 

the choking out at a stop could b alot of things...any other symptoms beside the dimming lights as it is most likely ur battery or alternator

 

do you turn the steering wheel at all. if you turn the steering wheel while ideling or close to the RPMs drop and lights might dim because of the pump that turns when the wheels turn because it draws allot of power, this is normal

 

I would not think turning the wheel would cause the dimming of lights and inconsitant idling. I know my car does not do this.

 

My Monte was doint that when I bought it from a PO that didn't do some prety basic maintenance.
Clean the Battery Connections
Make sure they're tight
Charge the Battery up ... Full Charge. (Then, hook-up a Volt Meter to the Battery to see what the Alternator is putting-out at 1,000 RPM's)
Replace the Air Filter
If the Air Filter is clogged-up ... several sensors are going to be getting fooled and try to adjust the Mixture to correct the situation.

Take the Car to AutoZone ... Have them Read the Codes for anything Pending. Get a Print-Out and do the Maintenance suggested.

 

when you turn your steering wheel and the vehicle is sitting still it does actually cause the rpms to drop slightly, but not 1/2, but yes turning the steering wheel while the vehicle is not moving take a little out of it

what year is your monte carlo?? it does sound like it could be a battery issue, however it could be other things too

i'd start with getting your battery tested

 

It could definitely be a bad sensor. Good call.

 

ok well now alot of things have been suggested but lets look at ur dimmed lights first. as jaws said ur power steering pump first thing first look under the hood and inspect the connections. if all is good go to autozone and get ur battery tested. if the battery tests good ask them to test ur alternator as well. if that checks out get the codes read...there may not be and continuos dtcs but the pcm also stored memory dtcs and that could b helpful. if there are codes let us know. get the dimmin lights straightened out first as a car cannot run without the battery. if your battery is not puttin out enough power to run the systems the car needs it may cause a bad idle. and this bad idle could only occur when ur alternator is not puttin out enough juice (like when at a stop sign or idle to shift) the only flaw in this theory is that ur car should not (notice i said SHOULD not) start because of a drained battery. so take these steps first and then let us know