Engine runs high idle/medium revs without lever action 2003 challenger X

[Hawk111]

Last year we were out on the water only a handful of times. The last day I noticed a little surging in the idle speed. When in neutral with the throttle lever at its lowest setting the idle speed is supposed to be smooth and at a low pleasant rev. Instead it would surge here and there like it was getting too much gas then it would rev back down. This year, I turn the key and it more or less floors it. I turn the key and it gos up to mid throttle and stays there on it’s own at mid revs. I’m not going to say it does right up to full acceleration on its own, but it does go up to mid acceleration/throttle on its own. What can I do to calm my engine down. It doesn’t appear to be a cable/mechanical issue. The little roller appears to be in the right spot. Could it be a choke issue? It thinks it’s on choke all the time now? For whatever reason the engine wants to throttle up to higher revs without me pushing on any levers? Please help.

 

[Shortrun]

I don't know you boat or engine.

On a 2 stroke engine there are 2 main reasons for uncontrolled revving of the engine.
If there is an air leak between engine and the carburetor (or fuel injection manifold) .
Or there are seals on each end of the crankshaft, if any seals are leaking they will let air into the engine and cause uncontrolled revving.
There may be other reasons for this on your engine.

Either way this is a very serious situation, it can damage you engine.

 

[Hawk111]

I don't know you boat or engine.

On a 2 stroke engine there are 2 main reasons for uncontrolled revving of the engine.
If there is an air leak between engine and the carburetor (or fuel injection manifold) .
Or there are seals on each end of the crankshaft, if any seals are leaking they will let air into the engine and cause uncontrolled revving.
There may be other reasons for this on your engine.

Either way this is a very serious situation, it can damage you engine.

Damage the engine, even if the water hose is on and connected? It’s the 2003 240 jet merc. You don’t think it could be throttle position sensor or temperature sensor failure? Again, 2003 mercury 240 jet. I got the vessel view module to plug in and help diagnose. Of course the Bluetooth light on the module flashes but the smart craft light does not. I can’t get engine data with this new device which sucks. It was supposed to be compatible. Also, what I don’t get is how does it suddenly idle and rev high without the intake flaps opening?Anyway, what next?

 

[Shortrun]

Also, what I don’t get is how does it suddenly idle and rev high without the intake flaps opening?Anyway, what next?

This is what I was trying to explain. Even if the intake butterfly valves are closed, if air is leaking in somewhere you can get high revving.

Damage can occur to the pistons. IF you have an air leak.
Nothing to do with whether there is good water cooling or not.

If you are mechanic minded you can check the spark plugs for color, this might tell you something. If you are not you should really get someone who is. The problem may be simple to fix. But IF damage occurs from running the engine the repair will not be simple or inexpensive.

I hope this helps.

 

[Tim75]

This is what I was trying to explain. Even if the intake butterfly valves are closed, if air is leaking in somewhere you can get high revving.

Damage can occur to the pistons. IF you have an air leak.
Nothing to do with whether there is good water cooling or not.

If you are mechanic minded you can check the spark plugs for color, this might tell you something. If you are not you should really get someone who is. The problem may be simple to fix. But IF damage occurs from running the engine the repair will not be simple or inexpensive.

I hope this helps.

I think Shortrun is on the right track.

Check all your bleed system hoses, especially the ends. Where they connect to the block. These hoses are known to crack over time and allow air into crankcase. 20 years. Replace with Tygon hose.

 

[Shortrun]

You don’t think it could be throttle position sensor or temperature sensor failure? Again, 2003 mercury 240 jet.

I really don't know about these causing your problem.
I suspect (but don't know) both of these do change how much fuel the injectors squirt in.
But the engine needs air to rev.

 

[POPPS]

Or,,,and I am not a merc tech,,,the fuel mixture is lean somewhere,,,that will cause the high idle, assuming it is not injected,,,just a thot,,,

 

[Hawk111]

It is EFI. But can the engine rev higher/idle higher without more air, but instead just more gas? What if there is more gas going in, causing the higher revving because the TPS sensor thinks the throttle position is higher than it should be? The weird part is the actual throttle still works. I did a minor mechanical adjustment with the whole throttle mechanical arm assembly by the engine. This appeared to help, but then went back to surging and ultimately a prettty high continous rev. Then I turned engine right off as always when it goes to high. And Tim75, what is a bleed system hose? Also, is there some kind of code fault reader I can put on this thing? I tried VesselView view but it won’t pair. Please help with all questions.

 

[Tim75]

It is EFI. But can the engine rev higher/idle higher without more air, but instead just more gas? What if there is more gas going in, causing the higher revving because the TPS sensor thinks the throttle position is higher than it should be? The weird part is the actual throttle still works. I did a minor mechanical adjustment with the whole throttle mechanical arm assembly by the engine. This appeared to help, but then went back to surging and ultimately a prettty high continous rev. Then I turned engine right off as always when it goes to high. And Tim75, what is a bleed system hose? Also, is there some kind of code fault reader I can put on this thing? I tried VesselView view but it won’t pair. Please help with all questions.

Engine damage from over-revving with no load. Piston damage from overly lean condition. You can melt the dome of one or more pistons running hot under load.

Too much fuel is hard on spark plugs by fouling. Too much air , covered above.

Bleed system hoses are the small black hoses that pick up pooled gas inside the engine and send it where it will go through the engine and be burned, not just go overboard.

What kind of "minor mechanical adjustment" did you do? These adjustments usually don't change.

Can you quantify "pretty high continous rev"?

Looking for a scanner- Merc proprietary. They show up on ebay . Expensive.

Have you done a compression test? All plugs out, WOT.

TPS controls fuel from about 15% to 80% throttle.

You said this is an EFI engine. As such, it has no choke.

 

[POPPS]

Would appear to be an air/vacuum leak somewhere, Tim is on the right track.

 

[Hawk111]

I am going to try and find this “air leak.” Post back soon when and if I find something.

 

[Hawk111]

Tried the old carb cleaner/flammable spray trick. Ran the engine on garden hose. I then sprayed this stuff all around the engine in different spots where there are seams and potential areas for leaks. Sprayed everywhere, nothing. Then, I sprayed underneath moving fly wheel. Then engine accelerated/revved higher. I was able to reproduce the resulting revving 4-5 times. Then, once it found the leak, the engine started revving high again on its own - the ghost revving.

I thought maybe I mis-sprayed and it went down the intake hole and caused acceleration. It did not. I’m thinking top crank seal. I also, sprayed directly into the air intake hole and it de-celerated a hair lol.

Sounds dumb, but how many hours do you guys think it would take to replace top crank seal. I know I should do both, but cash. Do I really have to remove engine to do this? It’s essentially a pressed in seal/bearing right? Remove fly wheel and it’s right there underneath. Any way to remove without splitting engine?

 

[Tim75]

Tried the old carb cleaner/flammable spray trick. Ran the engine on garden hose. I then sprayed this stuff all around the engine in different spots where there are seams and potential areas for leaks. Sprayed everywhere, nothing. Then, I sprayed underneath moving fly wheel. Then engine accelerated/revved higher. I was able to reproduce the resulting revving 4-5 times. Then, once it found the leak, the engine started revving high again on its own - the ghost revving.

I thought maybe I mis-sprayed and it went down the intake hole and caused acceleration. It did not. I’m thinking top crank seal. I also, sprayed directly into the air intake hole and it de-celerated a hair lol.

Sounds dumb, but how many hours do you guys think it would take to replace top crank seal. I know I should do both, but cash. Do I really have to remove engine to do this? It’s essentially a pressed in seal/bearing right? Remove fly wheel and it’s right there underneath. Any way to remove without splitting engine?

After you get the flywheel off, stator, and trigger out of the way, you have a better view.
I believe the top bearing and seal are in a removable housing. There are ways remove only the seal, but are a little risky. Might take 2 hours.

Keep an eye open for damaged bleed hose. Crank seals have not been an issue.

 

[Hawk111]

After you get the flywheel off, stator, and trigger out of the way, you have a better view.
I believe the top bearing and seal are in a removable housing. There are ways remove only the seal, but are a little risky. Might take 2 hours.

Keep an eye open for damaged bleed hose. Crank seals have not been an issue.

What is and where is the bleed hose that could be damaged? The risky maneuver involving drywall screws and yanking essentially? Can you please provide me a link to the upper crank seal of the 240 jet? I want to make sure I’m buying the right part. Also, any pictures of this removable housing? And considering the fact that the engine revved higher when I sprayed underneath the moving flywheel, do you think it’s safe to say, the crank seal is bad? It appeared that the spray was drawn in through the leak and accelerated the engine. I was able to reproduce this 4-5 times. Funny thing, I talked to one guy and he says he thinks that’s the issue. I talked with another mechanic and they don’t think that’s the problem.

 

[Shortrun]

Can you post a picture of where you were spraying? Pictures are better than words.

 

[Tim75]

What is and where is the bleed hose that could be damaged? The risky maneuver involving drywall screws and yanking essentially? Can you please provide me a link to the upper crank seal of the 240 jet? I want to make sure I’m buying the right part. Also, any pictures of this removable housing? And considering the fact that the engine revved higher when I sprayed underneath the moving flywheel, do you think it’s safe to say, the crank seal is bad? It appeared that the spray was drawn in through the leak and accelerated the engine. I was able to reproduce this 4-5 times. Funny thing, I talked to one guy and he says he thinks that’s the issue. I talked with another mechanic and they don’t think that’s the problem.

if you don't have the service book yet, you need it now. There are diagrams clearly explaining bleed hoses. There are pictures of the upper bearing carrier and seal. If you have a bad crank seal, you would be the first.

If you try to replace the seal without disassembly, using drywall or sheet metal screws. You will need to make holes in the old seal by PIERCING. Do not drill. You will introduce chips into the engine. If your piercing tool goes too deep, you may damage the bearing. The new seal needs to be installed evenly and to the proper depth.

Far, far, far easier is checking all the bleed hoses.

Seal part number from any local or online Merc dealer. You will need the serial number.

 

[Shortrun]

Tim.
I asked hawk to show where he was spraying, exactly.
What I was curious about is if there may be a seal problem with the upper intake manifold.
Have you ever seen problems in this area/

 

[Tim75]

Tim.
I asked hawk to show where he was spraying, exactly.
What I was curious about is if there may be a seal problem with the upper intake manifold.
Have you ever seen problems in this area/

Has the manifold been off lately? It could have been put back together without all the surfaces being clean. Imagine- the old gasket shreds and leaves pieces on one face. New gasket in place over old pieces. A made to order leak.

Yes, there is a bleed hose in that area.

 

[Hawk111]

Can you post a picture of where you were spraying? Pictures are better than words.

I sprayed underneath the bottom teeth of the flyweel disc the belt goes around, not the actual big flywheel disc teeth on the top . This pulley is mounted underneath the flywheel for the belt. I sprayed in the crack underneath. If the crank seal didn’t draw in the flammable spray, something else did. It’s accelerated each time I sprayed into the crack underneath this.

 

[Shortrun]

See my attached picture. Is there any chance your spray was making it way down to where my arrow is pointing?

This would be a much easier fix than the crankshaft seal will be. So i think it is worth investigating.

 

[Shortrun]

This might be the hose Tim is wondering about. The yellow hose.
this hose would be the easiest fix.

Your's will be a black rubber hose it it is still original.

 

[Tim75]

This might be the hose Tim is wondering about. The yellow hose.
this hose would be the easiest fix.

Your's will be a black rubber hose it it is still original.

Yep. Those yellow hoses are just some of the bleed hoses. They are on both sides of the block. The OEM hoses are known to crack at the ends and cause air leaks. It is even possible to break off one of the nipples the hose fit on. They are only small brass with a hole in them that makes them even weaker.

 

[Hawk111]

I sprayed underneath the bottom teeth of the flyweel disc the belt goes around, not the actual big flywheel disc teeth on the top . This pulley is mounted underneath the flywheel for the belt. I sprayed in the crack underneath. If the crank seal didn’t draw in the flammable spray, something else did. It’s accelerated each time I sprayed into the crack underneath this.

Yep. Those yellow hoses are just some of the bleed hoses. They are on both sides of the block. The OEM hoses are known to crack at the ends and cause air leaks. It is even possible to break off one of the nipples the hose fit on. They are only small brass with a hole in them that makes them even weaker.

Thanks for the response. I do not have the same engine as in your photos, shortrun. Mine is not a 2002 or before. I have the 2003 with alternator on the top and oil tank on side. I also still don’t know what these hoses bleed. Air, fuel? Here is my engine. I sprayed all around that “before reed” joint where throttle body meets engine body. No increase in revs. Can you see the bleed hoses? I can’t. Anyone have the link to the flywheel removal tool lol. I hope it comes off and goes on the same way and I don’t have to worry about timing. Like one of those toothed crank shaft ends.

 

[Tim75]

Thanks for the response. I do not have the same engine as in your photos, shortrun. Mine is not a 2002 or before. I have the 2003 with alternator on the top and oil tank on side. I also still don’t know what these hoses bleed. Air, fuel? Here is my engine. I sprayed all around that “before reed” joint where throttle body meets engine body. No increase in revs. Can you see the bleed hoses? I can’t. Anyone have the link to the flywheel removal tool lol. I hope it comes off and goes on the same way and I don’t have to worry about timing. Like one of those toothed crank shaft ends.

Flywheel removal tools avail. on ebay. It makes removal very easy. No change in timing.

 

[Shortrun]

Download the manual here from this site.
http://www.seadooforum.com/manuals/2002_240FI.pdf

page 3C-8 shows the oil lines. Including the one that connects to the the top crankshaft bearing.
and page 4A-33 has a very nice picture of hose routing.
All this for your model of engine.