My car is an 89 Trans Am 350 TPI. When idling in drive, the idle surges back and forth between about 600 and 1000 rpm. In neutral and in park, the car idles smoothly with no surging at all. It only happens when the car is in gear. What's causing this? Any help would be greatly appreciated.

Thanks
Chris

 

If its only happening under a load, then it might very well be a vacuum leak. However, stock MAF systems can be very tempermental. Even with no codes being thrown, I'd still make sure that all my connections are good (no pulled wires), and are each (each wire) giving adequate 'juice'...

 

check the resistence at the injectors, when in gear the idle is lower, so you can tell that it is surging, but when its idleing its a little bit higher rpm, it is probably still surging, you probably just cant tell. happened to me, changed injectors, works fine now