Volvo Repair: Over Drive, fuel mixture, drive question

Question
QUESTION:  I ask last week about overdrive jerking till bout 15 miles.  Now it's not working at all.  Will not come on. Light comes on.  Driving a 55 less than 3000 rpm will it hurt the tramsmission?

ANSWER: No it shouldn't hurt the transmission.

---------- FOLLOW-UP ----------

QUESTION:  Thanks so much for all your help. I got a new problem, I start the car. While setting still in neutal it revs up by it self from from 900 rpm to 2000 rmp up and down and sometimes it cuts off.
I'm sorry if I'm a pain.  I'm poor I gave $1000 for the car So I would have someting to drive to work till we get my wife's car fixed.  Which looks like $900.  If I can fix it my self and save money.  And We thanks with all our heart!

Answer
No problem at all, thats why I'm here.These year/model cars are known to have wiring harness problems. The insulation on the wires breaks down and allows the wires to short against each other.The most common place for this is at the intake manifold about cylinder 3/4.Thats a possibility. It could also be just a dirty throttle body and the air idle motor is trying to compensate, causing a surgeing.The throttle body would need to be removed to clean it properly.Install a new gasket, it is only three bolts and a hose clamp, clean with carburetor cleaner, no abrasive wire or tool.Reset the base idle afterwards and check the timing and fuel mixture.Manuals can often be found at the library to help you through the process.