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DanD
09-21-2006, 12:15 PM
I have a '99 Prostar 205 with the LT1 engine. I bought it used last summer and it has 140 hours on it. It stumbles when I try to get it on plane when it's cold. It runs okay once it is on plane. When it warms up, it seems to run fine. This started the first time out this spring after winterizing it last year. I called the dealer and they said it was probably a sensor and they could fix it if I brought it in. I'd like to fix it myself if possible. Does anybody have any ideas on what could be wrong?

rspiecha
09-21-2006, 12:45 PM
Contact tech support at www.skidim.com, they can usually tell you the sensor that needs to be replaced.

Rob

tdaines@hotmail.com
09-21-2006, 10:36 PM
It's probably the exhaust gas sensor. You can buy one at www.skidim.com and install in 3 minutes using an end-wrench. (Their tech support is awesome) I'm not positive where it's located on that boat, but likely on the underside of the exhaust manifold. Look for a single wire leading to it.

Good luck.

erkoehler
09-24-2006, 12:10 PM
If you take it to your dealer, they can check the engine to make sure that it is not putting out any "codes" and ensure that everything is running properly.

You do need to give the engines a bit of time to warm up before running them hard.

Farmer Ted
09-24-2006, 12:46 PM
I have a '99 Prostar 205 with the LT1 engine. I bought it used last summer and it has 140 hours on it. It stumbles when I try to get it on plane when it's cold. It runs okay once it is on plane. When it warms up, it seems to run fine. This started the first time out this spring after winterizing it last year. I called the dealer and they said it was probably a sensor and they could fix it if I brought it in. I'd like to fix it myself if possible. Does anybody have any ideas on what could be wrong?

When you first start the motor do you notice the sucking noise?

I had a problem with my LT1, it would run rough (could not hear the sucking noise), but if you goosed the throttle it would force the intake open (could hear the sucking noise)

I realize this is a highly technical way to troubleshoot something....

it turned out to be the IAC, easy part to change should be cheap (if you don't buy it from a MC dealer)

another thing to consider, when was the last time you changed your fuel filters? not sure about the 205, but my 190 has one on the engine and one on top of the fuel tank

DanD
09-24-2006, 01:22 PM
I do hear a sucking noise when I start the motor cold. Is this the IAC and does the sucking noise mean it's working correctly?

I talk to www.skidim.com and they said it could be the switch which is in the intake and tells the ECU to richen the mixture when cold. It's $20 so I thought I would change it and see if that fixes the problem.

I'm having trouble finding my fuel filter. I traced the fuel line all the way to the tank and I don't see a filter. There is a metal object on top of the tank that I thought was part of the fuel pump. Could this be the filter? If so, is it hard to change?

Thanks for all the help,

JimN
09-24-2006, 02:08 PM
There is no switch for cold weather operation. I have seen references to one in another forum and it doesn't exist. Why would they need a switch when the ECT (Engine Coolant Temperature) sensor tells the ECM that it's too cold to run the normal fuel table? The ECM is programmed to enrich the fuel mixture as the temperature drops (through the resistance of the sensor) and enleans it when the temperature increases.

Exhaust gas sensor? On a pre-2007 boat? The sensor on the new boats is an O2 sensor and they also added a catalytic converter. Boats have been running open-loop since they went to injection. The technology is not as up-to-date as cars and trucks.

Dan- if it stumbles when you try to get it on plane when cold, did you think that you should warm it to normal operating temperature? New boats won't even go above a set RPM if it isn't warmed up. All motors need to be at normal temp before going at those speeds, for a variety of reasons. I don't know how long you have had this boat but if you don't know the service history of it because the dealer or previous owner didn't tell you, having the dealer connect it to the diagnostic computer (if they know what they're doing) wouldn't be a bad idea, and doing a vacuum test would be a good thing to find out about the motor's general health.

Have you cleaned the flame arrestor? If your fuel pump is in the tank, the filter is on the bottom of the pump. Don't remove the round part on the top of the pump.

The IAC opens to set the idle speed as needed, based on temperature and the ECM will tell it to open/close so the motor hits the idle RPM in its program. If the RPM hunts wildly or is just too high/low, the IAC may be sticky or needs to be reparked. The IAC also follows the throttle. If you want to do more service on your boat, maybe you could take it in this time and see if you can be there when they work on it. Asking questions will undoubtedly increase the time it takes to do the work on it but the info you get should be worth it. They may not let you back there because if a problem occurs and parts go flying, they won't want to be liable. Some dealers will allow it, some won't. Also, some people don't like an audience when they're working.

Can you tell us more about whether the boat has had other preformance issues?

DanD
09-25-2006, 11:19 AM
The only peformance problem is the stumble when getting on plane when cold. I usually let it run for a few minutes before easing it on plane. I know it did not stumble last season, which is why I think something is wrong. Otherwise it runs fine.

I cleaned the flame arrestor and put some Techron in the tank. This did not seem to help. When I winterized it last fall I sprayed fogging spray down the intake. Now I have learned I should have sprayed it in the plug holes. I wonder if I damaged something by spraying it down the intake. This is the only thing I can think of that might have cause the problem. The stumble appeared the first time I ran it this spring and has not gone away.

The fuel filter must be in the tank. It looks like a bit of work to get it out. I am leaning towards taking it to the dealer. It's a lot of work for me to get it to the dealer which is why I wanted to try to fix it myself. Any more ideas?

JimN
09-25-2006, 11:53 AM
Spraying fogging oil into the intake won't hurt anything. If you saw a good amount of smoke after spraying it in, you're fine. Another place to spray it is into the PCV hose. Remove the hose from the PCV valve and pinch the hose to control the RPM (remember, this creates an uncontrolled intake leak). Spray it in and release the pressure on the hose to pull in more air and oil, which causes the oil to atomize better and will get into all of the cylinders because of the sudden increase in velocity. Once this is done, and if you want to "kill" the motor with the fogging oil go ahead, you can spray it directly into each cylinder.

One thing to remember about fogging oil and having it sit all winter is that the plugs are fouled and will need to be cleaned or replaced. I recommend doing the regular winterization stuff in fall but wait till spring to change the plugs after getting it started, in order to burn out the fogging oil. If you didn't change the plugs in spring, they're probably gunked up. If your plug wires are too old, you'll have the same problems. You may notice some backfiring when it's cold and this could be due to cross-fire.

Do a compression/cylinder leakdown test to eliminate that as a possible cause. Then, check the fuel pressure and take a fuel sample. Check your spark intensity if you can and see if it runs OK then. A drop in fuel pressure on hard acceleration will cause this kind of issue- you'll need to put a pressure gauge on it while you run it. If you can, have a second person there to either drive or monitor the pressure.

Your profile shows that you're an engineer- you need to think like one in situations like this. I can understand being PO'd and wondering why it's running badly but thinking logically and without any emotion is what's needed.