if you don't cap the vac line to the engine then it is gone to idle ruff due to a vac leak he is saying to not cap off the sensor. and no not capping the sensor is not gone to cause idle issues.. and the EEC is getting a reading from the map still just not from the engine. it now is reading atmospheric pressure
Yes the map becomes a baro on mass air systems. The baro's nipple must be left open. If your having problems with the engine starting then stalling, there may be a low fuel pressure concern. Do you have a pressure gauge to test that? Do you have a code reader? Is the PCM the correct one for mass air? Where do you have the large gauge ground (normally black/green stripe) coming from the PCM's 40 and 60 pins? Since you have a trunked battery, that ground should go back to the battery neg. cable. Joe, you have both of my 5.0L swap dvd's and volume two has a long detailed chapter on "no start" troubleshooting which should help you out with this problem. Also if your PCM is for mass air, is the MAF sensor the right one for that PCM. If you think the MAF is bad, you could unplug it and start the engine. If it runs better, you may have a bad or wrong MAF sensor. Keep working at it Joe and update you findings.