Hi - I own a 1998 RR with a 4.6L that I just completed an engine swap in with another 4.6L. Since dropping it it I had difficulty starting it and when it did with help of the accelerator it shut down quickly. Doing some research I learned that the MAF can be the cause of this so disconnected this after checking for spark and correct fuel pressure in the rail. Engine started with help on the accelerator and would stay running but very rough. It loves to accelerate and fires evenly during that but holding a given RPM it seems to be missing. I had used all the original sensors and beforehand had no such issues. I started to probe the harness after looking at manuals and made an interesting discovery. The Sensor ground which goes to many of the engine sensors and is typically a Red/Black wire coming from the ECU(Connector C507 Pin 36 is sitting at 5V with respect to Chassis ground. This is with the battery connected, the ignition on and all teh sensors connected. I then removed the connectors from the ECU and confirmed the 4 grounds that are supposed to be giving the ECU it's chassis ground - all good. I then checked for a connection between Pin 36 and some of the sensor grounds (with Red/Black coloring) and got good less than 1 Ohm) readings. It seems that the ECU is supposed to supply a ground to the sensors but is not doing so and one of the sensors is passing through a 5V reference through a coil or something. Can anyone confirm that indeed the ECU does supply a ground and whether that ground is there all the time or only when ignition is activated or at some point later when you got a closed loop condition. I have looked high and low for any information regarding this and all I have found is in the gemsbypoole.pdf where is states that this pin should be at 0V. Mine is not. I have a modified ECU that bypassed the imnmobilizer but this has been converted for years. I don't see how that would have a connection in this case. Any help appreciated... I also cannot find schematics for the GEMS8 ECU that would help me confirm this.