I'll give a little background so my problem may seem a little easier to diag. I bought my '88 351w A/T and everything ran fine, just leaked oil and threw a intermittent CEL for the EGR. Put it in the air and it seemed like the valve covers were the problem. Took everything apart to get to them. No major problems taking them off or getting them back on. Put everything back together with new gaskets (plenum and throttle body). I also put new plugs (Motorcraft coppers) while I was in there.

Now when I start the vehicle cold, it'll start fine and sometimes idle ok. When I put it in drive then put it back in park, the rpms will jump to 1500 - 2000 and will sit there, sometimes dropping back down to 1000. I'll shut it off and when I go to start it back up, it drags as if it doesn't want to start and if it does, it's a real rough start with the rpms sitting high.

I tried looking over the work, but can't seem to find why it's doing this from what I have done.

 

check your IAC and TPS. but first check it for codes! also after you finished, did you disconnect your battery for at least 5 minutes to clear the codes?

 

The battery was disconnect the whole time. I'll run a scan with my scan tool later to see what I get.

 

These are the codes she's throwing:

KOEO:
DTC 32: EGR pressure feedback fault

DTC 51: ECT Sensor out of range indicated / circuit open


KOER:
DTC 21: Cooling temperature sensor out of specified range or ect out of range

DTC 44: Thermactur air system fault

DTC 32: EGR pressure feedback fault

DTC 77: Operator error during dynamic response test / wide open throttle not sensed