1989 Volvo 244 DL. Just the past few days when I try to start the car, it would crank just fine, but struggle to turn over. With a little help from the gas pedal, you can get it to start, but it has never had this problem before. Even after it turns over, it seems to idle very low, to the point of almost stalling. I went to adjust the idle at the thumb screw on the throttle and realized that that part on the throttle body appears to have gone missing. I'm assuming it fell off somehow in driving? So, two questions:
1. Is there more than just the screw that fell off? If it is just the screw, where can I get a replacement?
2. Would a missing screw on the throttle cause the starting/idling problems?

Thanks ahead of time for the advice and help.

Doug