pinkhippo72
Cadet
- Joined
- Jun 27, 2011
- Messages
- 6
Hello,
We've been troubleshooting for several weeks so any help would be greatly appreciated... Here's the issue: Our Mercury 175 EFI will start up and run really rough and shudder at idle (around 500 rpm). If left to idle it will die usually within a couple of minutes. If we try to advance the throttle at all it dies immediately. The really weird thing is that sometimes it will run fine with no explanation, so it must be some kind of intermittent problem. What's very odd is that we tried to determine if any cylinders weren't firing by removing one plug at a time to see if it ran the same... we could remove ANY combination of 2 wires from one side (bank) of cylinders and it would run the same. So we couldn't isolate any particular bad cylinder, just that it would run the same when some wires, even different ones, were pulled. Weird, I know.
Here's what we have done: Complete trouble shooting of fuel system to include new fuel (have run from external fuel cell as well), new fuel filters, new lines, new fuel bulb, confirmed operation of fuel pumps and regulator through pressure tests and flow tests. Also checked vapor separator float. It has new spark plugs which have been confirmed to be getting spark and fuel. Compression is good on all cylinders.
So if there is spark, fuel and compression, what could be causing it to run poorly and die? Possibly a timing issue or an improper air/fuel mixture causing it to not fire correctly despite having all 3 components??? Other possibilities could be bad port side temp sensor which would make the ECU send an improper fuel mixture, maybe a bad throttle position sensor?
Any advice or suggestions, or wild shots in the dark
would be greatly appreciated!
Thanks a lot,
Meg
We've been troubleshooting for several weeks so any help would be greatly appreciated... Here's the issue: Our Mercury 175 EFI will start up and run really rough and shudder at idle (around 500 rpm). If left to idle it will die usually within a couple of minutes. If we try to advance the throttle at all it dies immediately. The really weird thing is that sometimes it will run fine with no explanation, so it must be some kind of intermittent problem. What's very odd is that we tried to determine if any cylinders weren't firing by removing one plug at a time to see if it ran the same... we could remove ANY combination of 2 wires from one side (bank) of cylinders and it would run the same. So we couldn't isolate any particular bad cylinder, just that it would run the same when some wires, even different ones, were pulled. Weird, I know.
Here's what we have done: Complete trouble shooting of fuel system to include new fuel (have run from external fuel cell as well), new fuel filters, new lines, new fuel bulb, confirmed operation of fuel pumps and regulator through pressure tests and flow tests. Also checked vapor separator float. It has new spark plugs which have been confirmed to be getting spark and fuel. Compression is good on all cylinders.
So if there is spark, fuel and compression, what could be causing it to run poorly and die? Possibly a timing issue or an improper air/fuel mixture causing it to not fire correctly despite having all 3 components??? Other possibilities could be bad port side temp sensor which would make the ECU send an improper fuel mixture, maybe a bad throttle position sensor?
Any advice or suggestions, or wild shots in the dark
would be greatly appreciated!Thanks a lot,
Meg