So after losing my first engine with 700 hrs because of 2 bad injectors I install a rebuilt 350 mag MPI long block. With all original peripherals from the old engine.
Original Engine Serial Number M350MPIB3 W042371
On first start up the engine idols perfectly. But when trying to throttle up anything over 1500 to 2000 rpms the runs rough surging drastically.
So first had mobile marine mechanic out with mercruiser computer he had no answer to the problem.
So another mechanic came out and suggested to disconnect the TPS and wow the engine throttled up with no hesitation. I replaced and check voltages at the new TPS and checked out fine. Yet the engine still will not throttle up.
Things that have been completed
1 New cap and rotor
2 New oil pressure switch
3 Plug wires tested and verified firing order
4 New Plugs
5 Monitored fuel pressure 40PSI
6) All injectors tested
7 Checked compression all 90 psi low but engine has only run for maybe 1 hr so I hope break-in will improve compression.
8 All done under no load just throttle.
Questions
1 Thinking it is electrical problem
2 The TPS must be seen by the ECM or it would not run better when disconnected
3 Could it be a bad map sensor? I tried disconnection map sensor and it started but immediately stalled
4 Could it be a bad ECM?
5 Does the TPS need some sort of calibration for ECM to see it properly like in some cars?
6 Could a rebuild be far enough off where the original ECM can't run it properly?
Thank for any Ideas
Joe
Original Engine Serial Number M350MPIB3 W042371
On first start up the engine idols perfectly. But when trying to throttle up anything over 1500 to 2000 rpms the runs rough surging drastically.
So first had mobile marine mechanic out with mercruiser computer he had no answer to the problem.
So another mechanic came out and suggested to disconnect the TPS and wow the engine throttled up with no hesitation. I replaced and check voltages at the new TPS and checked out fine. Yet the engine still will not throttle up.
Things that have been completed
1 New cap and rotor
2 New oil pressure switch
3 Plug wires tested and verified firing order
4 New Plugs
5 Monitored fuel pressure 40PSI
6) All injectors tested
7 Checked compression all 90 psi low but engine has only run for maybe 1 hr so I hope break-in will improve compression.
8 All done under no load just throttle.
Questions
1 Thinking it is electrical problem
2 The TPS must be seen by the ECM or it would not run better when disconnected
3 Could it be a bad map sensor? I tried disconnection map sensor and it started but immediately stalled
4 Could it be a bad ECM?
5 Does the TPS need some sort of calibration for ECM to see it properly like in some cars?
6 Could a rebuild be far enough off where the original ECM can't run it properly?
Thank for any Ideas
Joe
