I just did a tune up on my GS300 by putting in new plugs, cap, rotor, wires, valve cover gaskets. I had to take most of the top part of the intake apart to do it. When i reinstalled the parts everything started right up. After it warms up the needle drops below 1 like it normally does but now it drops a little lower to where it wants to stall out. I have to tap the gas to get it from getting to low. It never stalls out but its close. I know I had some problems trying to put the cables back in there right position. The throttle cable wasnt touched but the middle cable was all over the place and I have no idea if these cables determine idle speed. I checked all the vacuum hoses and they seem to be right. Any suggestion! The car worked fine prior to the tune up. No check engine light and when I drive the car it works fine. Any suggestions

Its not the easiest set of plugs to change is it?
I had the same problem and cured it by disconnecting the battery for about half an hour and then putting it back on. The problem has never arisen again

If it ain't broke don't fix it, mine has done 160,000 miles, only changed the 4 accessible plugs, not ideal but could foresee problems you have

[quote name='SONIC' post='53783' date='May 26 2003, 07:17 AM']I just did a tune up on my GS300 by putting in new plugs, cap, rotor, wires, valve cover gaskets. I had to take most of the top part of the intake apart to do it. When i reinstalled the parts everything started right up. After it warms up the needle drops below 1 like it normally does but now it drops a little lower to where it wants to stall out. I have to tap the gas to get it from getting to low. It never stalls out but its close. I know I had some problems trying to put the cables back in there right position. The throttle cable wasnt touched but the middle cable was all over the place and I have no idea if these cables determine idle speed. I checked all the vacuum hoses and they seem to be right. Any suggestion! The car worked fine prior to the tune up. No check engine light and when I drive the car it works fine. Any suggestions [/quote]Check your vacuum pipes for crack and leaks

Did you replace any gaskets with new ones or re-use any?
Could be an air leak.

Had the same problem on my mk1 when i changed the plugs its usually that the caps on the leads havent seated right. The other thing that causes a strange idle is the vacuum tube o nthe top of the throttle body that sits under the strut brace (if you have one) the pies around this split very easily and the tube gets bent and distorted if thats got crushed in that will give an erratic idle