2002 GT-40 runs rough and skips

[crowpats]

I am having trouble getting my 2002 PCM GT-40 to run without skipping. I have replaced the plugs, cap, roter, wires... I ran the old gas dry, and refilled with 93 octane. It runs better, but there is a skip every few sec. across all RPMs. at idle there is an slight smell of gas in the exhaust. It is as if one of the cylinders does not fire, but there is no detectable pattern to the skipping. does anyone have any ideas on what could be causing the engine to run like this?

[peteSki]

I'm having a similar problem with my GT40, did you ever find out what was causing the problem?

[swooddc]

Mine was doing something similar and it turned out to be a broken distributer. I had replaced Plugs, cap, rotor, wires, fuel pumps, filters and gas. turned out to be the distributer, where the rotor attached to it was loose. it caused the timing to wobble making a miss here and there. grab the rotor and try to wiggle it. shouldn't move at all on the shaft. worth a try.

[peteSki]

Thanks I will check that. I too have replaced the plugs, wires, cap and rotor. I didn't notice the rotor had any play in it but I wasn't looking for it. Will check it again.

[JayG80]

2002 GT-40 runs rough and skips

Maybe try replace the filter in the FCC.

[peteSki]

RE: 2002 GT-40 runs rough and skips

Well, I took the boat into the dealer and he did a thorough check. Fuel pressure is good, plus he changed the fuel filter as well. All the electrics check out as well. The problem looks to be mechanical as a compression test revealed lower than normal pressure on a number of cylinders. They won't be able to do a leak test to determine whether the compression is leaking out of the rings or the valves until the new year so I'm left with it as is for now. I did put in some oil thickener called Stop Smoke by Nulon. This is meant for engines that are burning oil as a result of bad rings or valve seals. Although my GT40 is not burning oil, the product seems to be working as the missing did not happen during use over the past weekend. Although it has improved performance for the short term, I'm not certain if it's really a good sign... if this additive has helped compression by sealing up worn rings then I'm looking at a rebuild where the engine has to be removed from the boat. I'd rather this be a valve issue since pulling the heads off is quite simple and far less expensive than having the entire engine removed from the boat. We'll have to wait and see, at least for now it's running better and I'll get some use out of it over the Christmas period.

Pete

[8122pbrainard]

RE: 2002 GT-40 runs rough and skips

Pete,
Good luck with the engine. Sorry to hear about the miss turning out to be a bigger problem.

Pulling the engine really isn't a major project. Most mechanics doing a top end job will actually prefer to pull it rather than climbing in and out of the boat.

[peteSki]

I suppose you are right. I'm only looking at from a cost per hour charge that I know my dealer has. So even though taking out the engine is the preferred method to get it right it does mean extra cost. But then this is only the case if the rings need to be done.

With something like this though, I'm happy to pay the extra cost for the job to be done right, so if taking the engine out is the right way then that's fine. If the job is done right then I should have a near new engine that should last me years to come. Well worth it compared with a half *** job that only leads to future problems.

As a wise man once said, "if a job is worth doing it's worth doing right". Sounds good to me!

Pete

[bobchris]

I would say you have an injector issue and a couple are sticking open too long and flooding and washing down the cylinder wall in the process. That is why you have low compression as the rings are being worn away since the fuel is washing off the oil from the cylinder walls leading to excessive ware on the rings Too much fuel pressure will do the same.

[Teleman]

I would say you have an injector issue and a couple are sticking open too long

This sounds more reasonable. Unless the compression is so bad that fuel air mixture is getting beyond the burnable limits, the compression test will only tell you about how well the cylinder holds pressure. If the compression is that bad too, it will have many other effects under load. Typically the engine with bad cylinders will miss that cylinder at idle all the time. Not just periodically as you mentioned. I might be sceptical of the mechanic.

[peteSki]

Guys, much appreciated for the suggestions regarding the possible injector issue as opposed to rings or bad valve seats. A couple other symptoms have come up over the past few months that I didn't really think about, one was that the boat has been using more fuel than in past in the same conditions, and also a noticeable fuel smell just after starting when the engine is at temp and has been shut down for 3-6 minutes while changing skiers. Both of these tend to support the theory that some of the injectors may be injecting too much fuel or spraying the wrong pattern.

I'm lucky that I actually have a spare set of new injectors, so my plan is to get them serviced to make sure they are OK as I've had them for 3 years without use, install them, change the oil to remove the Nulon Stop Smoke and see how we go from there. The servicing on the injectors I think should be reasonable cost wise and I'm quite confident enough to change them myself as I've done so in the past.

My mechanic provided me with a report on each cylinder's compression dry and wet, all of them are ok except for 1 that seems to be way out. On inspecting the plugs the one in this cylinder appears the most wet compared to all others.

Unfortunately I won't be able to get them serviced until after the holidays, but for the moment it's running OK with the oil additive. Not a permanent solution but at least my family and I can use our boat during our time off.

Will post any progress.

Regards,

Pete

[gride300]

do you have 99$ an hour labor at your dealer too?

[peteSki]

do you have 99$ an hour labor at your dealer too?

Thankfully not that high, more like $60 USD with the current exchange rate from Aussie dollars to US.

[peteSki]

Progress Update

I had my spare set of injectors serviced and they checked out OK, so I installed them without too much trouble. The next day we used the boat for a full day and it ran fine with no missing, but it was running like this on the old injectors after putting in the oil thickener. I did notice 2 things though:

1) The boat seemed to not burn as much fuel. We went the entire day and only used just over half a tank. This is an improvement over the past few weeks where the same day would take almost the full tank.

2) The smell of fuel after starting is no longer there. This was coming out of the exhaust and was noticeable.

I'd say these are good signs that it was indeed the injectors that were causing the problem, but I still need to change the oil to remove the thickener additive. I plan to do this at my next regular oil change which is in about 15 engine hours. If it runs fine after that then I won't need to have the engine rebuilt. A follow up compression test after the oil change is probably a good idea as well just to compare to the previous test to see if the compression has come up on the low cylinders.

Pete

[bobchris]

it's pretty much a waist of time doing another compression test, the rings are worn in the cyclinder and there's nothing that is going to fix it on it's own, the damage is all ready done and not reversible. Have the set you removed cleaned and seviced for spares later on down the road, but use the oil additive and call it a day until the rest of the cylinders start losing compression and you need to rebuild the engine.