2008 Optimax 200hp SN: 1B529252 high idle when in neutral

[Buscar]

Hi There,

Looking for help with high idle problem. The motor starts fine and idles fine, then I when take it for a run and come off plane and back down to idle in gear it is still fine until I put the throttle in neutral, then the idle jumps up to maybe 1000rpm. If I shut the motor down and restart, it's back to normal idle. This happens periodically and I have felt the odd slight surge when idling in gear but very rarely. I am think I may need to replace the TPS.

Any ideas are much appreciated...

[EuropeanAM]

Check to make sure the throttle arm on the side of the engine is being CONSISTENTLY and FIRMLY returned to the idle stop screw. It is extremely critical that this occur (both for the PCM's ability to "learn" idle AND FOR SAFETY.

If you have a hotfoot- it should be inspected for debris in and about the hotfoot, lubricate all pivots and moving points, and make sure that the return spring is adjusted to permit CONSISTENT and FULL return to the idle stop.

[Buscar]

Thanks EuropeanAM...No hotfoot. Without a hotfoot would it be ok to check the idle stop and return by putting the throttle in gear engine off or do i need to do this in the water with engine running?

Thanks for your help

[Savage]

You can do it on land, but make sure that you just work the throttle, and not the gear shifter.

[Buscar]

I checked it repeatedly and the idle stop screw is seating firmly and the throttle cam and roller return to the proper postion. linkages also look good with no excessive play. I think it could be a faulty TPS since it is intermittent and it always returns to normal idle when I shut down the motor and restart but I am not getting any alarms. I am assuming the PCM is not picking a fault in that rpm range.

[Buscar]

I checked it repeatedly and the idle stop screw is seating firmly and the throttle cam and roller return to the proper postion. linkages also look good with no excessive play. I think it could be a faulty TPS since it is intermittent and it always returns to normal idle when I shut down the motor and restart but I am not getting any alarms. I am assuming the PCM is not picking a fault in that rpm range.

I was told if it was the TPS causing the high idle it would trigger an alarm. I am not sure if that is true..i read the neutral overspeed alarm can trigger at 1200rpm so if it is 1000rpm, then it wouldn't trigger an alarm. Can anybody confirm this please?

[apdriver]

I had the exact same thing happen with an intermittent high idle, some small uncommanded throttle changes while in gear. Could restart it and it would return to normal. Followed Dons advice and changed the TPS and two other parts that is a part of it. Cover and linkage, I think. Fixed it. I never got any alarms.

[EuropeanAM]

I was told if it was the TPS causing the high idle it would trigger an alarm. I am not sure if that is true..i read the neutral overspeed alarm can trigger at 1200rpm so if it is 1000rpm, then it wouldn't trigger an alarm. Can anybody confirm this please?

Fault is only triggered if the sensor's value is OUT OF RANGE (ie: Below the minimum reading, above the maximum reading, drops below the LEARNED idle position, open circuit or short circuit). So a sensor that simply reads high when the throttle returns to idle will not cause a fault (the PCM will presume the throttle is partially open).

In re: Your PM about throttle cable adjustment, if the cable is tight enough against the stop to tear a piece of notebook paper that is between the stop screw and the block, the cable needs to be adjusted. See Factory Service Manual for cable adjustment procedures.

[Buscar]

Thank you for taking the time to reply Don,

I was able to get into my merc service centre and the tech swept voltage on TPS. It had a reading of .7 volts at the idle stop. I asked him to replace it and he took a reading afterwards and it was 0 everytime. He did some engine run testing and did not get a high ilde.

I hope that solved the problem ...Thanks for help guys.

[Savage]

.7 volt reading is not a bad reading at Idle position.

[lpugh]

Agreed and I would be quite concerned with 0 volts, Maybe this was throttle percentage, not volts read as the would make since

[EuropeanAM]

+1... suspect that was the Percentage/Position.