Have you ever encountered a 4 tech in a sportster that has a mid range surge? I am estimating we are experiencing about a 300 rpm variance in RPM under steady throttle.
The engine starts easily and idles smoothly. About the time it comes on plane, it starts this surge, or RPM fluctuation, until about 3/4 throttle, then it smooths out and the RPM's no longer fluctuate.
I do not know the history behind this problem. I got the boat after it had sunk sitting on a beach where the engine was under water. I got the engine up and running, but now have this surge. I don't know if it is a pre-existing condition before the sinking or related to the engine being submerged.
I had the boat checked by a sea doo dealer and they did not find any codes to indicate a component as a problem.
In trying various tests today, it was discovered that if the maps was unplugged and the hose for the intake was removed from the air box and partially restricted by hand, there was a specific point where the surge could be overcome and the engine picked up RPM. It was a very subtle difference between overcoming the surge and either having it or choking too much air off. That notwithstanding, this would indicate to me that I am experiencing a lean condition.
The service manual does not go into any detail about if a certain sensor is unplugged, simulating a complete failure of it, whether the system defaults to a pre-determined curve or program that will allow the vessel to return to port.
One time today the check engine light came on. After the engine was shut off and restarted, it never came back on, other than when we unplugged other sensors trying to isolate the problem. The check engine light went out right away when we plugged the various sensors back in. On previous lake tests, I had the surge but never got a check engine light.
I had one person suggest that the intake manifolds were susceptible to air leaks. We started the engine and sprayed contact cleaner on the mating surfaces and did not produce any change in idle RPM. Normally, on an engine that has an air leak, that would kill the engine, or at least audibly alter the idle to indicate the contact cleaner was being ingested.
Also, a running fuel pressure test was performed. The fuel pump instantly created 45 psi of fuel pressure, and never varied the entire RPM range, even though the surge was quite noticeable.
My questions are, 1.) Have you ever heard of or had a 4 tech surge?
2.)What controls or dictates the injector pulse cycle to control rich/lean?
The manual does not go into any detail about how each sensor affects the ECM, and if it isn't throwing a code, the manual is of little help. They generically say that a component could be within resistance specs, but still not be functioning, or it could be the ECM. That is all well and good IF you have known good parts to throw at it for the sake of testing. It is of no value if you are unable to freely swap parts and see what happens.
I am hoping someone has some insight from a previous similar experience so I don't have to spend money needlessly trying components that may not be bad.
Thanks
RSRBOB
The engine starts easily and idles smoothly. About the time it comes on plane, it starts this surge, or RPM fluctuation, until about 3/4 throttle, then it smooths out and the RPM's no longer fluctuate.
I do not know the history behind this problem. I got the boat after it had sunk sitting on a beach where the engine was under water. I got the engine up and running, but now have this surge. I don't know if it is a pre-existing condition before the sinking or related to the engine being submerged.
I had the boat checked by a sea doo dealer and they did not find any codes to indicate a component as a problem.
In trying various tests today, it was discovered that if the maps was unplugged and the hose for the intake was removed from the air box and partially restricted by hand, there was a specific point where the surge could be overcome and the engine picked up RPM. It was a very subtle difference between overcoming the surge and either having it or choking too much air off. That notwithstanding, this would indicate to me that I am experiencing a lean condition.
The service manual does not go into any detail about if a certain sensor is unplugged, simulating a complete failure of it, whether the system defaults to a pre-determined curve or program that will allow the vessel to return to port.
One time today the check engine light came on. After the engine was shut off and restarted, it never came back on, other than when we unplugged other sensors trying to isolate the problem. The check engine light went out right away when we plugged the various sensors back in. On previous lake tests, I had the surge but never got a check engine light.
I had one person suggest that the intake manifolds were susceptible to air leaks. We started the engine and sprayed contact cleaner on the mating surfaces and did not produce any change in idle RPM. Normally, on an engine that has an air leak, that would kill the engine, or at least audibly alter the idle to indicate the contact cleaner was being ingested.
Also, a running fuel pressure test was performed. The fuel pump instantly created 45 psi of fuel pressure, and never varied the entire RPM range, even though the surge was quite noticeable.
My questions are, 1.) Have you ever heard of or had a 4 tech surge?
2.)What controls or dictates the injector pulse cycle to control rich/lean?
The manual does not go into any detail about how each sensor affects the ECM, and if it isn't throwing a code, the manual is of little help. They generically say that a component could be within resistance specs, but still not be functioning, or it could be the ECM. That is all well and good IF you have known good parts to throw at it for the sake of testing. It is of no value if you are unable to freely swap parts and see what happens.
I am hoping someone has some insight from a previous similar experience so I don't have to spend money needlessly trying components that may not be bad.
Thanks
RSRBOB
