Engine has rough idle and missing on acceleration
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Et. al,
496HO MPI no modifications. Normal engine maintenance schedule followed.
This is what I am experiencing. This has never happened before and just started last week.
At cold start-up it has a rough/choppy idle and seems to smell a little rich. When I start to accelerate (while not at operating temps) to plane it has the same feel as if there are dead cylinders with a definite loss of power. Once on plane and with the remote at between full and 3/4 throttle it has intermittent missing then will clear itself up and run normal with no missing, with normal idle.
Gauges: Oil pressure ~ 40-50psi, volts 12(+) Temp <160.....
Once at normal operating temps 160-170 it wont duplicate the problem and runs like normal.
Anyone experience this problem that seems to be related to first start-up and disappears when at operating temps?
No service bulletins related to this problem that we could find.
Here is what I have done so far:
- Checked plugs (all are fine)
- Ohm the plug wires (all are good)
- All connections to injectors and coils are fine
- Siphoned all the non-ethanol gas, replaced with new non-ethanol (just in case. Put the siphoned fuel in my vehicle and it ran fine)
- Fuel filter has ~ 25 hours on it. (there is no fuel/water separator)
- Flame arrestor is fine.
- Scanned for any codes, no codes found or produced (this was done by my local Merc dealer) we were thinking temp sensor causing timing changes.......
- Anti-freeze was changed last year.
Any ideas??????????
496HO MPI no modifications. Normal engine maintenance schedule followed.
This is what I am experiencing. This has never happened before and just started last week.
At cold start-up it has a rough/choppy idle and seems to smell a little rich. When I start to accelerate (while not at operating temps) to plane it has the same feel as if there are dead cylinders with a definite loss of power. Once on plane and with the remote at between full and 3/4 throttle it has intermittent missing then will clear itself up and run normal with no missing, with normal idle.
Gauges: Oil pressure ~ 40-50psi, volts 12(+) Temp <160.....
Once at normal operating temps 160-170 it wont duplicate the problem and runs like normal.
Anyone experience this problem that seems to be related to first start-up and disappears when at operating temps?
No service bulletins related to this problem that we could find.
Here is what I have done so far:
- Checked plugs (all are fine)
- Ohm the plug wires (all are good)
- All connections to injectors and coils are fine
- Siphoned all the non-ethanol gas, replaced with new non-ethanol (just in case. Put the siphoned fuel in my vehicle and it ran fine)
- Fuel filter has ~ 25 hours on it. (there is no fuel/water separator)
- Flame arrestor is fine.
- Scanned for any codes, no codes found or produced (this was done by my local Merc dealer) we were thinking temp sensor causing timing changes.......
- Anti-freeze was changed last year.
Any ideas??????????
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I am about to swap out my ignition coil which is causing the exact symptoms you are giving. I have not taken it out yet with the new coil but after much research I am pretty sure this is causing my issues. The issues are exactly to a tee what you are saying. I can barely get on plane until the engine warms up.
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Bad injector...take a long screwdriver and put it on each injector and have a listen..you should hear a clicking noise,,which ever one is not or has a faint clicking noise i would pull that injector and replace it..you can also ohme out the injectors to see if you have a bad one..
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I am about to swap out my ignition coil which is causing the exact symptoms you are giving. I have not taken it out yet with the new coil but after much research I am pretty sure this is causing my issues. The issues are exactly to a tee what you are saying. I can barely get on plane until the engine warms up.
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Bad injector...take a long screwdriver and put it on each injector and have a listen..you should hear a clicking noise,,which ever one is not or has a faint clicking noise i would pull that injector and replace it..you can also ohme out the injectors to see if you have a bad one..
Do you know the ohms range for the injectors?
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have no clue,,when you check then i usually go by lets say 3 of then ohme out at 12.9 then ill use that number as a referance,if i find one that is more then 1 ohme of from the others then i will suspect that one as a problem.. i will find the bad cylinder and ill hook my scope to it and look at the pattern..
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Just rough idle that continues when you try to get on plane.
Once at temp 160-170 it idles smooth with no missing when going on plane.
What sucks about trying to trouble shoot this problem is I have to let the engine get cold again.
Once at temp 160-170 it idles smooth with no missing when going on plane.
What sucks about trying to trouble shoot this problem is I have to let the engine get cold again.
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have no clue,,when you check then i usually go by lets say 3 of then ohme out at 12.9 then ill use that number as a referance,if i find one that is more then 1 ohme of from the others then i will suspect that one as a problem.. i will find the bad cylinder and ill hook my scope to it and look at the pattern..