87 jetta loping idle in drive

Hi guys, i have a 1987 jetta with the 1.8 and auto. While in drive and comming to a stop, the engine will try to stall. It will rev up, try to stall do this a few times then calm down and run fine. It will somestime do this when i first put it in drive and stall. no problems in park, neutral or reverse. Changed plugs, wires, cap, rotor, fuel & air filters but no change. Any help please.

Check the rubber boot that goes between the housing for the air filter and your intake manifold. It looks like a little rubber accordion that's about 6 inches long. Check it carefully. If it has a crack in it that lets in air it can really screw up your engine performance and make the engine run very rough. That can happen either when starting out (you lug the engine and it rocks on its mounts and then flexes that boot, thus opening up the crack and letting in an incorrect mixture of air). The boot is easy to remove and inspect. The first time I did it I was sure it was OK until I actually took it off. I inspected it carefully and there was a crack. I repaced it with an intact one...it solved the problem!