I have a 1989 f150 with a 302 engine the idle had gotten erratic going up and down in rpm's i replaced the mass sensor and now the idle is very low to the point of engine dyeing when in park but almost normal when in drive it has me baffled any suggestions

 

How did you get a MAF on your 89'. If in fact it is Mass air flow, After reaching normal operating temp. Disconnect the battery for 5 mins. Reconnect, restart, let idle for 2 mins.. Turn off for 1 min. Restart, put in gear w/ foot on the brake and let idle for 2 mins. then turn off for 1 min. See what you have for an idle now. This clears & rebuilds the KAM (Kept Adaptive Memory) based on a now functioning MAF sensor. This should take care of it if #1. It is MAF. #2. that was the only problem. If #1 or #2 or both are not correct, your idle will still suck after all that. A little better at best. So let me know & we'll go from there. Where specifically is that sensor located on your engine?