Well, Everything I have learned on my 633 has been trial an error and Yes a bit expensive. But these are great cars. Directly below my throttle body. there is a Idle control valve. this also controls the amount of air into the chamber. Here is how i tested mine. There is a screw on the top that you can control the amount of air. If you end up moving it and it does not control or change anything. Carefully remove the screw and try to cap it with your finger. If the car starts up replace that part. it runs for about 120 at NAPA auto parts. Remember my car is a 1984 model 633. I know that the 1988 635 models are different. I am not a mechanic, just some body that has gone thru a lot of fun times and i have success fully have had my car running. I drive my car every day to work a 120 mile round trip every day of the week. I have recently up graded my differential to a M6 model. I hope you can make it to the beemmer fest this year. its a good ego booster or a very humble experience in my case after you see some real cool machines.LOL.....Well hope it helps....
Last edited by Jrvna; 04-14-2011 at 07:37 AM.