Help? "Limp Home" mode kicking in for no reason... Not sure where to start?

[SuperAirIan]

This is completely different than the gt40. I could not find any info on it online.
Looks like a gm engine doe anyone know if this was used in a car or truck as well?
I also can't make out the actual control module where is it?

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[/QUOTE]

I believe it is that unit with the heat-sink...just in front of the Distributor...and under the 3 orange wires. Unbolt it to find the MPEC version labeled on the under-side of the ECM.

[SoldTheBayliner]

I will unbolt it and take a look... thanks. I ordered plugs, plug wires, distributor cap, and rotor... inquired with nautiqueparts.com about the ignition coil, and they came up with a part number (R117002) but "they do not show it as available anymore"... just got a follow up from them asking for the engine serial number. I will send that when I get home today... hopefully there's a Chevy equivalent out there if it comes to that. Fingers crossed that it's a simple misfire and the basic tune-up stuff will fix it...

[nyryan2001]

FYI... I ran a standard GM autozone ignition coil from autozone till my PCM ignition coil arrived.... 100% exactly the same coil. Match a standard 5.7 engine coil side by side.

who was it on here said cap/rotor engines don’t have ignition coils? Lol

[nyryan2001]

And I would recommend you replace these parts in phases if you are cost sensitive. You may be able to return the unused and unnecessary parts for a refund if you can find the issue.

recommend swap order, each followed by a water test if you have time:

1. Ignition coil
2. Plug wires
3. Plugs
4. Cap/rotor

[SoldTheBayliner]

Awesome... thanks for the confirmation there. pulling it off and taking it to Napa was my plan B... did that for the heater core and saved a few hundred bucks. haha.

Nautiqueparts came back and wanted the engine serial number to figure out a coil... waiting to hear if they can come up with a part #... sounds like the stock one isn't made anymore.

I ordered plugs, wires, cap, and rotor already... If that doesn't fix it, I figure it's probably time for that tune-up stuff anyway, so not a huge loss. That box will show up early next week and I'll move on to the coil if that doesn't cure it.


What's still throwing me off is that once it misfires, it continues running like that. If it's a bad spark, it would either miss from the get-go, or miss as the timing advanced and then spring back to life at a happier RPM, yeah? What does it just keep missing once it starts missing? Does that point to electrical/coil?

[nyryan2001]

Coil. Bad engine coil would perfectly for 5 mins till it warmed up, then wobbly limp.

restart boat. 45 seconds above 2k RPMs then wobble limp.

restart boat, 30 seconds above 2k RPMs then wobble limp.

keep it under 2k RPMs, no limp, no wobble.

swap out 1 bad coil, 100% perfect, 25hrs since.

[SoldTheBayliner]

That makes sense... the only difference is that mine will run sweet at higher RPMs for as long as you want... then slow it down for a bit, and it freaks out... so I'm not convinced it's the coil getting warm and then causing problems.


I got my box of goodies today and swapped out the cap, rotor, plug wires, and plugs.

Distributor cap had some definite corrosion going on...



You can see a bit of crust/corrosion at every terminal. Matching gunk on the rotor, and on the distributor cap mounting plate:



I hit it all with electrical contact cleaner and wire brushed/blew off all the crud that I could before sticking the new cap and rotor on there. The plugs didn't look alarmingly bad... they were all about the same with no one plug showing any signs of one cylinder running too rich or too lean. About normal for 19 year old spark plugs:




I got the new wires on there without losing track of what went where... hooked a hose up in the driveway and fired it up just to make sure I didn't screw anything up. It fired up instantly and was noticeably smooth to me. Not going to be able to really test it until I get it on the water, but I have high hopes... if this doesn't fix it, I'll do the coil. Haven't heard back yet from NautiqueParts about a coil option. I sent them the engine serial number a few days ago...

Taking it out tomorrow, and we'll see..... I also have the new fuel filter in there, haven't run it with that either... not that that is related, but.....

EDIT: I did gap the plugs myself at .045 which is what the sticker on the engine specified...

[SoldTheBayliner]

Well.... no dice. Same symptoms. Ran buttery smooth otherwise though. Still haven’t heard back from NautiqueParts on a coil.....

[SoldTheBayliner]

Well I feel a little better if PCM doesn't know either. haha. Looks just like the one on 97-03 GM trucks with the 5.7 when I google search it... am I going to have any output voltage problems or anything if I gamble on that?

[SoldTheBayliner]

OK, progress... sent a pic and NautiqueParts confirmed with PCM... got a part # on the coil: R117005
Special order, not on the website...
sticking it on here for the next guy that goes through this.....

So, I'm ordering the coil, and hopefully that does the trick. Should run like a champ by the time I'm done throwing parts on it. haha.

[nyryan2001]

Keep us updated pls

[dico2020]

Hi, Just something to check but we had an issue on our 03 san where the wire on the v drive sensor ( Cant remember if temp or pressure) was dodgy and it put our boat into limp mode. without the wire it acts like normal but as soon as you go over 1200rpm it hits limp mode.

[dico2020]

Thinking out loud again, What if it is the water temp/ oil temp/ pressure sensor or what ever it is) on the vdrive tranny and at lower rpm its not pumping enough oil or water thus engaging limp mode? The boat sounds like its fine at rev's...

[SoldTheBayliner]

^^ That sensor isn't on the Vdrive, it's right off of the block. And disconnecting it so it couldn't send a fault, it is still happening.

Coil is supposed to be here today and we're hitting the lake over Labor Day weekend... talking to my car guys, and they agree that it makes sense that a weak coil would run good at higher RPMs when it's getting more juice, and start getting weak at lower RPMs when it's not getting as much from the alternator. They're telling me that if it isn't coil, it's alternator. We shall see...

[SoldTheBayliner]

Ok update... I’m at the lake for the weekend. New coil is slightly different in appearance... plugs are the same but the mounting plate is different. It will only mount with one bolt instead of two because of the difference. I assume it’s identical in output because it came direct from PCM after they got the engine serial number.

but that may be irrelevant because it didn’t fix my problem. Boooo. Straight out from the dock I put it at about 2k rpms and held it there, about 10mph... ran sweet for about 5 minutes and then boom... non limp mode limp mode. Missing and the usual feel. Runs like a top at higher speeds. Duplicated this a couple times. Shut it off, turn it back on, runs good for a while and then starts cutting out. So no surfing, and no little kids on the tube or the boat won’t run. I’m completely at a loss. Not even sure what else I could throw money at. Alternator?

I also checked the check engine out light finally... it works. Doesn’t come on when this is happening, but it comes on when I turn the ignition on before I start the boat.

So thus far: new impeller, fuel filter, knock sensor, disconnected limp mode sensors, new plugs, plug wires, distributor cap, rotor, and coil. Plus $500 for the shop to try to fix it. It’s throwing no codes. Oil pressure and temp are perfect.

What next?