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Sunday was the first day out for us this year and we had a problem we've never had before.
Our boat is a 99 Sport with GT-40 and 1.23:1 PCM transmission that only has 152 hours total.
In the past we have always had a hunting idle problem but never any issues under throttle. The engine has performed flawlessly other than the hunting idle issue.
But this last time out it was a little rough idleing and died a couple times when I first started it up while launching. Once warmed up it idled perfectly and did not hunt at all. I could not give it more than 1/2 throttle though without it cutting out really bad. Anything below that and it ran perfectly. It would cruise fine at any throttle position up to 2500 rpm as well.
The thing is it seemed like the 2500rpm limit was the magic number as I could ease up to that point on the tach and if I gave it even a fraction more throttle it would not hesitate in response to throttle input but as soon as the tach needle passed 2500rpm it would start hesitating and slow down. Keep it at or 2500 and it purred along without a hitch.
Temp guage never showed it overheating and IIRC the oil pressure looked fine too.
I serviced it just a month ago changing the oil/filter, transmission fluid and drained the FCC and changed it's filter as well.
Also, the check engine light was on the whole time. I have tried searching on here for a clue to the problem and saw a few posts about limp mode and the oil pressure sensor.
I have some experience troubleshooting EEC-IV systems in cars and have most of the tools I need to test sensors. I don't have a code scanner but do know how to use a multimeter and jumper wire to do a Key On Engine Off Test for codes.
Here are my thoughts on things to test before taking the boat to the lake for a water test. I don't have any way to test run the engine out of the water right now.
1. Check the TPS to make sure it has the proper voltage sweep for closed to full throttle.
2. If possible use an automotive code scanner or use the multimeter and jumper wire method to pull codes during KOEO mode.
3. Test or change the oil pressure sensor and engine coolant temperature sensor since those are easy enough and cheap enough to replace.
So what do you guys think? Any ideas? Any thing I can quickly and easily do to troubleshoot this during the week before taking it back to the lake?
Thanks.
Our boat is a 99 Sport with GT-40 and 1.23:1 PCM transmission that only has 152 hours total.
In the past we have always had a hunting idle problem but never any issues under throttle. The engine has performed flawlessly other than the hunting idle issue.
But this last time out it was a little rough idleing and died a couple times when I first started it up while launching. Once warmed up it idled perfectly and did not hunt at all. I could not give it more than 1/2 throttle though without it cutting out really bad. Anything below that and it ran perfectly. It would cruise fine at any throttle position up to 2500 rpm as well.
The thing is it seemed like the 2500rpm limit was the magic number as I could ease up to that point on the tach and if I gave it even a fraction more throttle it would not hesitate in response to throttle input but as soon as the tach needle passed 2500rpm it would start hesitating and slow down. Keep it at or 2500 and it purred along without a hitch.
Temp guage never showed it overheating and IIRC the oil pressure looked fine too.
I serviced it just a month ago changing the oil/filter, transmission fluid and drained the FCC and changed it's filter as well.
Also, the check engine light was on the whole time. I have tried searching on here for a clue to the problem and saw a few posts about limp mode and the oil pressure sensor.
I have some experience troubleshooting EEC-IV systems in cars and have most of the tools I need to test sensors. I don't have a code scanner but do know how to use a multimeter and jumper wire to do a Key On Engine Off Test for codes.
Here are my thoughts on things to test before taking the boat to the lake for a water test. I don't have any way to test run the engine out of the water right now.
1. Check the TPS to make sure it has the proper voltage sweep for closed to full throttle.
2. If possible use an automotive code scanner or use the multimeter and jumper wire method to pull codes during KOEO mode.
3. Test or change the oil pressure sensor and engine coolant temperature sensor since those are easy enough and cheap enough to replace.
So what do you guys think? Any ideas? Any thing I can quickly and easily do to troubleshoot this during the week before taking it back to the lake?
Thanks.
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