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srh99vlx

Rough running Monsoon

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srh99vlx

This is a follow up to an earlier post. My new to me 99 VLX with the Monsoon is still not fixed. I have owned it for about 3 months and haven't enjoyed it one moment yet. My mechanic just got the diagnostic cables, so I took it back to him last week. He ran a scan. No codes were set. If you reset the computer by unhooking the battery. The boat cranks up, idles very smoothly. It runs fine initially for up to 5 minutes or so. If you run it up to around 3500 RPM's and then back down to idle, it starts running rough and tries to quit or quits running. If you try to give it gas, it runs rough and backfires. It does this intermittently, which I can only assume this is why it didn't happen on the test drive. I have had about two periods of about 10 minutes where it runs fine, but it seems to do this about 8 out of 10 times. Here is what we have tried: Cap/Rotors/Plugs, TPS and IAC, fuel filters. Anybody got any other ideas. My mechanic is at a loss and Indmar suggested most of the things above. He is bringing a Chevy car mechanic in to see if he has any fresh ideas. I am at a loss, I just want to get the boat out on the water, it is torture not having ever used it.

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electricjohn

Does it always start easily when cold, then act up after it is warmed up?

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Skiier64
Does it always start easily when cold, then act up after it is warmed up?

Just a few suggestions. I would try a new engine temp sensor. They are fairly cheap and easy to replace. Also, has anyone screwed around with the idle stop screw? I had a similar problem with mine after I tried to adjust the idle stop screw (which I know now you shouldn't do on an EFI engine). If the screw is not at factory setting, it will mess the ECM up and idle rough and backfire when pushing on the throttle. You also might want to check for any kind of vacume leaks in hoses or anywhere in the intake manifold gasket.

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Hman442

I second the water temp sensor - the two wire one - I think in the intake, the one wire one would be for the gauge. Also, lean makes them pop - the mechanic should be able to test fuel pressure.

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srh99vlx

It smells like it is running rich instead of lean. That is why we went with a new IAC, thinking it was starved for air, not fuel. I will ask him about the idle stop screw and temp sensor. Would a bad temp sensor throw a code? He and I both thought that the diagnostics check was going to tell us something, but we really didn't get anything out of it. Also, the computer doesn't go into a fail safe mode, the Indmar tech support department said that this mode would keep the engine RPM's under 2000. You can rev it up past 2000 when it is in this mode, it just doesn't rev smoothly and then dies as soon as you go back to idle.

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srh99vlx

Also, it doesn't matter if it is cold or warm. It doesn't happen initially after cranking if you have unhooked the battery. However, after it has been brought up to 3300-3500 RPM's the first time and allowed to go back to idle, this is when it starts. If you shut it down and crank it up again after it sets into this pattern, then on the second cranking it runs rough from the get go. It will run rough with each crank after that, eventually won't crank back up and then you have to unhook the battery to get it to crank back up again. That is why we thought some computer code was being set off.

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electricjohn

A bad (open or shorted) eng. temp. sensor would throw a code, one operating out of its calibrated range would not. Same goes for the MAP sensor.

I do not know if the knock sensor is connected to the ECM or EST on a 99 Monsoon, but if it is connected to the EST and failed, you also would not get a code. Make sure it is connected.

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srh99vlx

You guys are helping a lot. I am putting together a list of things that I am going to take to my mechanic. Now I have to prioritize and see which one is the first to try and so on. Here is what I have so far from this thread and in talking to other people:

Engine Temp Sensor

Idle stop screw

Vacuum leak/hoses

Check oil pressure with a mechanical gauge

Check temp with manual gauge

Drain Gas tank/run off new gas or run off an accessory tank

MAP sensor

Knock Sensor

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jgouveia3

i wonder if this is ethanol related (which has effected many outboards in our area, and it seems that there are an awful lot of questions about lower rpms and engines in general this year on this site).

Have you had the injectors cleaned (professional, not just by trying to blow them clean with compressed air - check out online, their are places that do this specifically).

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srh99vlx

I may have to have the injectors cleaned eventually, but will probably try some of these other things first. I have asked several times about running the boat off a different tank thinking something might be in the tank, but the mechanic has looked at the gas several times and he doesn't think it is running like it is bad gas because it does the same thing almost every time. The fact that you can reset the computer and it runs like a dream initially argues against it having bad gas in the tank.

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Skiier64
I may have to have the injectors cleaned eventually, but will probably try some of these other things first. I have asked several times about running the boat off a different tank thinking something might be in the tank, but the mechanic has looked at the gas several times and he doesn't think it is running like it is bad gas because it does the same thing almost every time. The fact that you can reset the computer and it runs like a dream initially argues against it having bad gas in the tank.

When I had the the problem with my monsoon running rough, it also smelled like it was running rich and seemed to use a lot more fuel. My mechanic was at a loss. As I said before, it ended up being the idle stop screw out of adjustment (which I messed with). What I did to fix it was to take a measurement from my neighbors monsoon. I measured the distance between the idle lever and the screw base, and set mine the same. As mentioned above, it could also me a faulty fuel regulator, check your fuel pressure.

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srh99vlx

I spoke with my mechanic and he said that he unplugged the Engine Temp Senson, Knock and MAP sensor while doing the diagnostic test to see if they would throw codes. He said all of them did. He thinks they all appear to be functioning properly. He said he checked the idle stop screw and it still has the factory paint on it and hasn't been adjusted. He is still at a loss, looks like he will be bringing in a new mechanic to get a fresh perspective.

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chris.h.

I had a similar problem when I first bought my boat. It was a rough running, backfiring gas hog. The thermostat was stuck wide open and would not allow the engine to warm up completely. It usually stayed around 100 deg water temp. With a new thermostat she runs just fine. I was new to Malibu and did not know what the temp was "supposed" to be. After some forum searching on this site, I have learned a ton. Not sure if a thermostat would fix your problem but a cheap fix if it is.

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Liquidmx

Did you check the timing to make sure its timed properly? Something easy to verify.

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srh99vlx

Mechanic checked the timing when he changed the cap/rotors/plugs and then verified it with the software. I may have him check the thermostat, it seems to come up to around 140 or so, but it is worth a shot.

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Liquidmx

Any updates?

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srh99vlx

Thanks for asking, I am going over there today to take off the tower speakers and throw them up on eBay since I got some new ones. I will see if the new mechanic has come in yet. If he hasn't, I will probably take the boat 30 miles on down the road to the Bu dealership. I would have started there, but i have known this mechanic for a good while and he has always been honest and straight shooting with me in the past. I think he has just been dumbfounded and since he spends all his time working on PCM's, he knows all the tricks to try with them, but not necessarily on an Indmar.

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srh99vlx

Didn't get by the mechanic's today, going tomorrow morning. I did talk to him and the other mechanic hasn't come by yet. I may be moving it to the Malibu dealership. I was trying to be patient so these two mechanics could communicate about what had already been done, but it is getting a little ridiculous. He has had my boat almost 2 months off and on with no solution yet and I am looking at a holiday weekend coming up, so this new mechanic probably want even come over to look at it until after the 4th (speculation, but likely reality).

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hocklawski
Does it always start easily when cold, then act up after it is warmed up?

This sounds like the problem we are having with our Malibu Response Lxi. The motor always starts beautifully, then if we just stop it for a few minutes (between skiers) then it starts up again no problem, but if we stop the motor for more than 15 minutes, it won't restart (actually it will sometimes start and then run rough and then stop or sometimes won't start at all) then you have to wait another 1/2 hour to 2 hours for it to restart.

I'm getting really frustrated. I've talked to other malibu owners that had similar problems but they've all said it's a fuel filter problem but I've had the fuel filter replaced and the mesh screen cleaned.

any suggestions?

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maniac mechanic

New to the forum. Just reading about your problem. Temp sensor are notorious for going out of range on GM engines. A shorted ETS will read -44 F. An ETS often fails at high temps also which makes them hard to start when cold. These conditions will not necessarily set a code but should show up on engine data. Should be a routine check. Fuel pressure at different temps would be valuable information.

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srh99vlx

I think I am going to have him replace the temp sensor, for 20 bucks, it could be the ticket. I'll also have him check for a wide open thermostat that somebody else mentioned.

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srh99vlx

Update: Temp sensor wasn't the ticket, the other mechanic that was supposed to look at it threaded me along for two weeks, so now it is going to the Malibu dealership. They have a two week wait time, but what's a little more time right?

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Surfin247
Does it always start easily when cold, then act up after it is warmed up?

This sounds like the problem we are having with our Malibu Response Lxi. The motor always starts beautifully, then if we just stop it for a few minutes (between skiers) then it starts up again no problem, but if we stop the motor for more than 15 minutes, it won't restart (actually it will sometimes start and then run rough and then stop or sometimes won't start at all) then you have to wait another 1/2 hour to 2 hours for it to restart.

I'm getting really frustrated. I've talked to other malibu owners that had similar problems but they've all said it's a fuel filter problem but I've had the fuel filter replaced and the mesh screen cleaned.

any suggestions?

My 2005 vride did the same thing. My fuel pump is on the side of the engine block (aluminum canister). If yours is, I bet when this problem happens your fuel pump is very hot to the touch. Next time try cooling it off. Put wet towel on it, pour water on it (Not saltwater) wedge a cold beverage on it. Once it is cooled down it should start. If you want to avoid this in the first place, run your blower for awhile after running it hard and leave the hatch open when the boat is just sitting to let the heat out. I think this is why Malibu has recently gone to fuel pump's in the gas tank on their models. The gas keeps the fuel pump cool. Cooling the fuel pump has worked for me everytime, but one other trick I saw in a manual was to turn the ignition key on , but don't start the engine. Let the fuel pump turn on and run, when it stops repeat 1 or 2 more times, then start the engine. This is supposed to clear the pump and fuel rails of any vapor. The problem is fuel vapor in your fuel pump and it can't push vapor,only liquid. I call it vapor lock, but some disagree. I don't argue with results. Once the fuel pump is cooled down, everything runs perfectly, every time.

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srh99vlx

I wish I had an answer, mine doesn't seem to be vapor lock as I have seen it start running rough in as little as a minute after cycling through the throttle and coming back to idle.

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Surfin247
I wish I had an answer, mine doesn't seem to be vapor lock as I have seen it start running rough in as little as a minute after cycling through the throttle and coming back to idle.
Sorry for the hijack I was refering to hocklawski, not your problem. Your problem kind of sounds like our old boat, but its a carby and the choke was stuck closed. The boat was running rich. You could run it hard, but as soon as you came back to idle it would bog down and stall. Yours is EFI, so sensors,fuelrail ,injectors, regulator, fuel pump, It sounds like runnig rich, like others have said. Try a fuel pressure gauge while recreating the problem.

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