The engine is a fresh rebuild due to a cracked block. The engine ran great when it was tested on a hose, brought it to the lake and about 1 minute into the first run it started cutting out and misfiring. After troubleshooting for awhile finally figure out that the fuel pump water-cooled fuel cells orings had failed and let water into the fuel system. As I was loading the boat back onto the trailer the shift cable also seized up. Shift cable and fuel pump has since been replaced. Now the boat idles rough, fluctuates between 450-550 rpm, has slight hesitation when I start to throttle up and surges between 500-800 rpm as I throttle up and run smoothly once it goes to 1000+ rpm. Once I throttle down the engine stalls if i don’t throttle down very slowly. On a cold starts the throttle has to be cracked open or it will fire up and die repeatedly. Once warmed up it will fire up with out cracking the throttle but still idles rough with all the symptoms mentioned. Her is a list of what all I have checked and replaced.
* Fuel Pump – High Pressure 40 psi Low Pressure 8psi
* New fuel water separation filter
* Injectors have been flow tested and cleaned
* Pulled vacuum line from regulator and vacuum line is free of fuel, high pressure psi shoots up 5 psi when regulator is unhooked.
* Ran a hose from fuel pump to a gallon of fresh gas to rule out water in the fuel tank, no change in the way it ran. Also pulled a fuel sample from the high pressure line, fuel is clean, no contamination present.
*Vacuum pulls at 14” at idle
*Smoke tested for vacuum leak, no leaks present
*Tested for fire with spark tester, all cylinders have spark.
* New spark plugs
*New spark plug wires
*New MAP, Throttle Position, Idle Air Control, and Crank Position Sensors.
*TPS shows 0% at idle and verified that the throttle body is completely closed at idle.
* Verified IAC pintle is reacting when key turns over and engine fires up. Cold start IAC is around 96 counts, once warm it never falls below 60 counts. Is this normal? From what I’ve read IAC should be between 20-40 counts on a warm engine.
* Removed and thoroughly cleaned the throttle body
* Checked all ground cables, they were all clean, tight, and showed continuity back to the ecm.
* Purchased a scanner from OBD diagnostics to scan for codes, sensor outputs, etc. No codes present and from what I can tell everything looks as it should.
* Sent the ECM to Bob at OBD diagnostics and everything checks out good on the ECM.
Any help would be appreciated as I’m out of Ideas. I’ve been troubleshooting this issue for about a month now after spending my entire summer rebuilding the engine. I'm really hoping I can get it figured out before I have to winterize the boat. I’m planning on taking the boat to the lake tomorrow and running it for a while to see how it does, possibly the ecm needs to relearn?
* Fuel Pump – High Pressure 40 psi Low Pressure 8psi
* New fuel water separation filter
* Injectors have been flow tested and cleaned
* Pulled vacuum line from regulator and vacuum line is free of fuel, high pressure psi shoots up 5 psi when regulator is unhooked.
* Ran a hose from fuel pump to a gallon of fresh gas to rule out water in the fuel tank, no change in the way it ran. Also pulled a fuel sample from the high pressure line, fuel is clean, no contamination present.
*Vacuum pulls at 14” at idle
*Smoke tested for vacuum leak, no leaks present
*Tested for fire with spark tester, all cylinders have spark.
* New spark plugs
*New spark plug wires
*New MAP, Throttle Position, Idle Air Control, and Crank Position Sensors.
*TPS shows 0% at idle and verified that the throttle body is completely closed at idle.
* Verified IAC pintle is reacting when key turns over and engine fires up. Cold start IAC is around 96 counts, once warm it never falls below 60 counts. Is this normal? From what I’ve read IAC should be between 20-40 counts on a warm engine.
* Removed and thoroughly cleaned the throttle body
* Checked all ground cables, they were all clean, tight, and showed continuity back to the ecm.
* Purchased a scanner from OBD diagnostics to scan for codes, sensor outputs, etc. No codes present and from what I can tell everything looks as it should.
* Sent the ECM to Bob at OBD diagnostics and everything checks out good on the ECM.
Any help would be appreciated as I’m out of Ideas. I’ve been troubleshooting this issue for about a month now after spending my entire summer rebuilding the engine. I'm really hoping I can get it figured out before I have to winterize the boat. I’m planning on taking the boat to the lake tomorrow and running it for a while to see how it does, possibly the ecm needs to relearn?
