'97 GT-40 miss or sputter.

[ToddF]

That picture with the yellow arrow is the tfi module, typically it is placed on the distributor but it looks like they placed in a different location already, which could be good or bad depending on heat soak.

It also looks like the housing with the cooling fins was designed because of heat soak.

 

I would try the wire wiggle test on the tfi too, doubtful that is the cause.

But it should unbolt pretty easy,

one tip: the tfi is like a 4 or 5 mm bolt and most sockets don't fit in the plastic opening very well, so I have had to tap the socket in or have a thin wall socket to be able to get the bolts loose.

 

I know you replaced the MAP sensor, not sure if that is a BAP or MAP, the map will have a vacuum line going to the manifold the bap will just read the barometric pressure not manifold pressure, either way the boat would still run just crappy.

 

I used to keep a TFI module in my car just in case.

Now I keep a tps in my boat

[lakeside7455]

I think it may be the 2 fuel pumps, the small feeds larger one. This went out on mine, and was an easy fix. It's not getting the fuel because of bad pump is my guess.

[Wish]

@lakeside7455 we did a fuel pressure test at the injector rail and it was perfect in all driving conditions even with the miss. Thinkn not the fuel delivery system other then past the fuel rail..like the injectors themselves. But if one to those were bad even intermittently, I would think it would be a bigger issue then a millisecond miss. Add to that, a new coil fixed the issue for about 6 weeks.

[A_B]

I replaced everything on my ‘99 and it ended up being the ECM. Fuel pump pressure gauge revealed pressure was intermittently dropping and ended up due to a bad ECM. There is no code or test. You just eliminate everything else. It took me quite a while to eliminate all the possible pressure issues. New pumps, relays, I even pulled the tank and cleaned it out, new check valves on tank, kill switch, etc. Pain in the keister.

 

The big thing now is finding an ECM. If I still had one of those boats and wanted to keep it long term, I would buy a spare ECM. If I could have swapped one out at the onset I would have saved weeks and lots of money.

 

Good luck.

[Wish]

Ok the problem has gotten worse. Now it misses from the start. Idles ok but as soon as you throttle up..misses. So seems to be not heat related.

 

Today changed out the relays..nope. Changed out the TFI..nope.

 

History so far:

Fuel pressure tested fine in all conditions (although not retested since it's gotten worse in the last few outings)

No codes (again not tested since worse)

New cap and rotor

New plugs

New ignition coil (NOTE: which solved problem completely for weeks)

MAP sensor swap with new. No change.

New fuel filter and electric pass though

Tachometer seems perfectly functional

Low pressure pump only 200hrs on it

Wires have maybe 500hrs

 

Suggestions not tried yet;

Note: no longer seems temp related as it does it right off the bat.

 

Did not try temp sensor (for injectors)

Did not try TPS

Wires seem unlikely but not changed.

 

[JAS]

EEC is easy test. Find friend with GT-40, borrow his for a few hours and install in your boat. If all symptoms gone you have answer, if not guess keep looking. In 1999 EEC was reprogramed to help with idle speed at start up but otherwise the same. Lots of stuff on Planet Nautique if you do search.

[TEL]

Did you try another coil to see if it works again? not uncommon for a new part to go bad

[Wish]

@TEL forgot to add that. Yes I did try a new coil. No change.

[Wish]

@JAS EEC=ECM ...yes?

[JAS]

@Wish Yes

[jhughes]

Do you have that extra "+" wire with an inline fuse on it in the battery compartment? This was problematic on these boats if you have it.

[skiep]

A friend of mine had the exact same problem. Ended up being the bushing in the distributor, Made the rotor wobble back and forth causing the skip.

[Wish]

@jhughes. Had the redone by a professional about a year after I bought it.

 

@skep we had cap, rotor and lower cap adaptor off to check to see if the distribute shaft itself was solid...it is...very. I do not know how else to test it for issue. I did speak to your friend though. Similar problems for sure.

 

Guys, I really appreciate the suggestions. At the very least, if you have a GT40 motor in your boat, this may be a good thread to book mark. Gonna see if my neighbor is generous enough to let me barrow his ECM. It's a long shot though as I'm not sure he will. Anyone know if that's a straight forward plug and play swap or more complicated??

 

Still open to any and all suggestions. Thanks.

[JAS]

Plug and swap

[Killer]

@a_b. Nautiqueparts.com has reman units for 650 and some guys on PN also have a fix.

 

@jhughes can you elaborate on the + wire you mention?

[A_B]

I bought my ECM new years ago for around $350. If a reconditioned one is going for $650, I would buy one right now and keep it in a cool dry place. You will eventually need one!

 

I documented my process on Planet Nautique or some other Nautique owners forum. There were lots of tech guys helping along the way.

I posted video of the motor running great and then it sputtering while having the fuel pressure gauge hooked up, it was easy to see what was happening.

 

[A_B]

Here is a link to the CorrectCraft Fan thread from back in 2012 when my '99 SN was giving me problems.

 

You might have to join to read the thread. I just had to replace my old expired password.

 

 

 

 

[Wish]

Thanks @A_B

[A_B]

If you can get a ECM from a buddy’s boat do it. Not very hard to pop one in there.

 

I bought a fuel pressure gauge from autozone and that revealed what I thought was happening. It sounded like it was starving for fuel. Then it was figuring out why.

 

 

Relay switches. Cheap and easy fix.

Kill switch can be jumpered

Fuel filter in FCC

Fuel pumps

Anti siphon valves on tank

Tank pickup

 

That’s about it.

 

I suspect when I first started having a bit of trouble and replaced the relay switches, it might have just been coincidence that it worked good for a while.

 

The ECM is a fickle beast. Seems to slowly go bad very sporadically if you ask me. Causes lots of false diagnosis.

 

I had about 400 hours on a boat that was kept in mint condition in my garage year round. Just luck of the draw I guess.

 

 

[Wish]

@A_B similar to what u are saying with your relays helping for a while. The new coil helped (fixed it actually for weeks). Then the prob came back as it had been with getting in a full set no prob but 15 of boat sitting and could not get a second set without it missing. Now it misses from the very start (still idles ok) . :/

[A_B]

If you put a fuel pressure gauge on you can see if the pressure is fluctuating. If that is the case, the list I gave above is about all you can do. I put in new fuel pumps, filter, relays, anti-siphon valves, new kill switch, and found it was the ECM. Did you get your new filter? I didn't ever change one before and the new one did zero for the issue. I wouldn't mess with the tank like I did either. you can take off the anti-siphon valves and clean up with carb cleaner spray, they were cheap so I bought a new one. Once I plugged in the new ECM it ran like a beast again. My favorite boat of all time.

[DanE]

One thing you can try is listen very carefully near the FCC when you turn engine off. If it sounds kind of like the fuel pump is running for a second or two after you turned the key off it indicates that air has entered the fuel rail and will spin the fuel pump backwards a bit because of the compressed air in the rail.

This will make injectors shut off at random but the fuel pressure can still show a good reading. Drove me nuts when it happened to our club boat.

[TEL]

Since I have no cure for your boat the least we can do is give you a pull, if you need one. Skiing late tomorrow morning and early Saturday. I live on the same side of Orlando as you. Let me know

[BraceMaker]

@Wish by any chance does a local mechanic own a good oscilloscope and know how to use it?

 

I'd be very curious to see the graphs of your ignition and that's about the only way to verify if you have a spark related condition which will be very apparent on a scope.

 

 

[thager]

Time to take it to a "good mechanic" @Wish. At this point you are just wasting time and your money. Puff...puff.... Uncle!

[Wish]

@thager aargh...your right. Gonna take a shot at neighbors ECM first but ya...the white flag has been raised. :/

[VONMAN]

Fuel pick-up line in tank? If it's a rubber hose line, they get old and brittle after years of use. When I replaced my old one it fell apart in my hands. Could be cracked and sucking air.

[buechsr]

I'd try a new cap. Bad batches for a while there, and I spent hours tracking a problem on a new 350 this spring that was backfiring out the top and bottom. Didn't do cap right away since it was new. Turned out was bad from the start. For $45, try a new one. If bad, electricity can go to many cylinders its not intended.

[jhughes]

Excal swap w/ZO may be a couple bullets down on the list at this point.

[Wish]

@jhughes it's bubbling up to the top quickly. But I'd like to get through the summer as I have a local guy that can do and has done swaps but he prefers doing it in the winter when he's slow..(winter being relative in FL)

[DanE]

Wow, what a slalom tug that would be.

Better than most if not any of the new boats out there today.

[Wish]

@DanE promised my wife it was the last boat I'd ever buy. Said nothing about a repower. ;) The wakes are just too good. I'm not getting younger so long term, a TC1 hull is the best in the business when it comes to slower speeds longer lines. But that's a long way off.

[elr]

Coil wire

[Wish]

@elr it's new.

[VONMAN]

Fuel pick-up in tank??

[Wish]

Anyone in the Orlando area have a GT40 I can barrow the ECM for a test run down my lake?? I'll know if that's the fix in less then 100 feet.

[Tryathlete]

I did not see where you’ve replaced the clear plastic tube in the FCC with the rubber hose that Skidim sells. That plastic tube cracks and causes pressure drops.

 

I am thinking your problem is ignition related. As a matter of fact, I’m going to wager a guess it’s a single bad wire or bad cap contact. Swap out one wire at a time with a fresh one. It would not take more than 15 minutes to nail that possibility down.

[Wish]

@Tryathlete yes, that was changed out some time ago as you describe but did give it a good look over when I changed the filter and pass through. Am assuming your talking about plug wires. What's on it at not that old (maybe 500hrs) and are from PCM. Still could be that but have not changed any out.

[Tryathlete]

Every time you pull wires off of plugs you run a slight risk of ruining the terminal end. 500 hours isn’t so much the issue. Years take their toll. Get a good long wire from an unused set and just swap it in for each wire.

 

Also: Bad cap out of the box can be an issue. Check continuity from inside to each rotor contact outside the cap to make sure you’re ok there.

[Wish]

Well, so far replacing the entire distributer has solved the problem. Several test rides and 2 ski sets so far...knock on wood. Spoke to a PCM boat machanic and he basically said he would have gone through all of the ignition system items we did and that it would ultimately point to the distributer. There is no way to test just the dist as far as I know other then a full swap. I'm sure he would have done all of what we did just that much faster ?. Most everything I went through can be chalked up to maintenance and parts that were close to or needing to be changed out. Kept some of the old working parts as spares. Learned a lot so not horrible. Thanks for all the suggestions. Great place to get answers.

[Simpson]

This just happend to @aupatking put a new cap and button on and boom like new again. There was no sign of any problems with the old ones.

[Wish]

@Simpson we put a new cap and rotter on. Did nothing. After doing a bunch of other smaller things that did not help as well, we changed out the entire distributer (pictured). There's a sensor inside the dist that can get loose or just go bad. The michanical movement of the distributer felt good so assuming the sensor was bad (PIP sensor I believe it's called).

 

 

[skiep]

Wish, I guess i wasn't far off.

[Wish]

@skiep dead on man..dead on. Shoulda listened to ya when u mentioned it a month ago. Just seemed so extreme. But, I had to go though what was gone though to pin point that as the problem. Learning experience. ?