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| 86 OMC/GM motor misses problem |
| Author |
Message |
    
Christopher Lynch
Member
Username: katja9039
Post Number: 5
Registered: 05-2008
| | Posted on Saturday, May 10, 2008 - 08:40 pm: | 
|
The motor is a GM inline 4 cyl. I have it started now but the engine has a constant miss/rough idle. I tried to adjust the carb, I re-adjusted the valves per the manual, I double checked the timing. I have no idea what else to do to correct this problem does anyone have information that could help? Thanks |
Bob Hill
Advanced Member
Username: boatin_bob
Post Number: 564
Registered: 07-2006
| | Posted on Sunday, May 11, 2008 - 08:56 am: |
|
What year is this (OMC?) If you've gone as far as the valves I'm assuming you've pulled the spark plugs wires one at a time while running to see if you can find a dead cylinder (either plug, wire or valve). If this is an OMC with an ESA module, is it possible it's energized causing your miss? Quickest way to rule out the ESA is just unplug it, 2 wire plug wire purple and grey wires in it. |
Christopher Lynch
Member
Username: katja9039
Post Number: 7
Registered: 05-2008
| | Posted on Sunday, May 11, 2008 - 10:07 am: |
|
I will unplug the ESA today and see what happens. I do know some of the spark plugs seem to fire unsual. What will unplugging the ESA do? |
Bob Hill
Advanced Member
Username: boatin_bob
Post Number: 566
Registered: 07-2006
| | Posted on Sunday, May 11, 2008 - 11:27 am: |
|
The ESA module is an electronic device only meant to be energized during a gear change like going from forward to neutral and only for a couple of seconds. It is hooked to the negative post of your coil and it pulses the coil effectively grounding it out during these pulses. The effect it has causes the engine drop RPM's and it feels like it's almost going to stall, this allows the gears in the outdrive separate much easier making your shifting very easy (theoritcally) Unplugging it is a test that eliminates it as a potential cause for your current problem. |
Scott P
Visitor
| | Posted on Monday, May 26, 2008 - 12:50 pm: |
|
Wow this guy is good!! Thanks Boatin Bob. I was experiencing the same problem with my 1986 OMC 3 liter. Rebuilt the carb, tune up and still the same problem. Once the motor warmed up it ran rough and would not idle. Occasional it would surge, run OK for a short time then back to the running rough. I unplugged the ESA module and all is fine. Thanks again boatin Bob - tight lines!! |
Hy Stat
Advanced Member
Username: hystat
Post Number: 300
Registered: 05-2007
| | Posted on Monday, May 26, 2008 - 03:03 pm: |
|
As Bob says, the ESA has a definite function and purpose. Unplugging the ESA isn't the long term solution. You likely have lower shift cable problems that will lead to the destruction of your lower gearset if not addressed. |
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