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

[NautiqueJeff]

You guys saying overheat and oil pressure are the only two causes for limp... you don’t know that. All you know is those two definitely DO cause limp.

Well, I do have the e-mail referenced earlier in this thread from PCM that confirms this...

[SoldTheBayliner]

You guys saying overheat and oil pressure are the only two causes for limp... you don’t know that. All you know is those two definitely DO cause limp. There could be other issues related to the ECU that were not spelled out in that diagram that shows oil pressure and heat force a limp mode.

I Continue to believe it’s an ignition problem...whether cap and rotor, firing order, or something with the knock sensor.

I just saw this... exact same behavior as he describes. It was an ignition problem failing to ignite causing knock and then engine into limp mode.

This sounds likely... the limp mode thing is a mystery to me... if those are the only two sensors that can trip it and it only happens at higher RPMs and should go back to normal at lower RPMs, then I'm not experiencing limp mode... except that it feels EXACTLY like limp mode.... it's obviously a firing order or misfire or computer controlled timing thing that immediately resets itself.... so a "bad" switch or something sounds less likely than a computer controlled change in firing sequence...

I'm just not sure where to start throwing money to try to track it down at this point. Plugs, wires, cap and rotor are easy enough... maybe that next?? I put a new knock sensor in it at the beginning of this drama, no change after that. What fixed it in your case?

[SoldTheBayliner]

I don't have anything for the APEX version, does it use the same Ford ECU then the GT40?, If so oil and water or a defective ECU would be the only cause of SLOW mode.
I also believe this is a ignition issue.
Some pictures would really help to find out whats installed.
Peter

I don't know if it's the same as the GT40... I'll get some pics and post up... Thanks for the help.

[Peter6000]

If it has a distributor the ECU cannot change the firing order only timing.
Peter

[SoldTheBayliner]

Well, I do have the e-mail referenced earlier in this thread from PCM that confirms this...

I was thinking they might have mentioned it if there was something else.... haha. I'm taking that, and the doc you posted earlier talking about RPM during SLOW mode as evidence that what I'm experiencing is NOT limp/SLOW mode... considering that it happens with both of those switches disconnected. I'll confirm the check engine light next time out... when I turn the ignition on but don't start the boat in the driveway, the check engine light does not come on. Does that matter or mean anything? Someone mentioned that it should come on with the ignition.


Another point to make again is that it has been plugged into a computer at the shop and is not throwing any codes at all. Does that rule anything out? Would any of the ignition related stuff throw a code?

[Peter6000]

I was thinking they might have mentioned it if there was something else.... haha. I'm taking that, and the doc you posted earlier talking about RPM during SLOW mode as evidence that what I'm experiencing is NOT limp/SLOW mode... considering that it happens with both of those switches disconnected. I'll confirm the check engine light next time out... when I turn the ignition on but don't start the boat in the driveway, the check engine light does not come on. Does that matter or mean anything? Someone mentioned that it should come on with the ignition.


Another point to make again is that it has been plugged into a computer at the shop and is not throwing any codes at all. Does that rule anything out? Would any of the ignition related stuff throw a code?

If the Controler is the same you check engine light bulb may be broken.
The gt40 version also has a buzzer that should go off in SLOW.
Peter

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[SoldTheBayliner]

No buzzer when this happens. Not sure if it has one or not.....


Some pics. The Fuel Control Cell canister is removed at the moment, don't be thrown off by that.... I took the black plastic cover off (far right side of the first pic) for the other pics.

[nyryan2001]

I think the recommendation earlier to test ignition spark.... and confirm the firing order and/or timing or whichever of these applies. Absolutely replace cap, rotor, wires and spark plugs. Any of those could be resulting in a bad cylinder ignition. Get nifty red wires lol.

the reason why I’m so adamant about it...it was my boat over 3 separate days. Ended up being a defective ignition coil. Engine cold? I could run anything for 5-10 mins. Once it warmed up?... anything over 2k RPMs cylinder misfire, limp. Codes. Restart, keep it under 2k RPMs.. runs fine. Go above that, limp.

question: do you get a wired wobble or vibration when it happens?

[Peter6000]

No buzzer when this happens. Not sure if it has one or not.....


Some pics. The Fuel Control Cell canister is removed at the moment, don't be thrown off by that.... I took the black plastic cover off (far right side of the first pic) for the other pics.

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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[SoldTheBayliner]

question: do you get a wired wobble or vibration when it happens?

Only what feels like the engine running super rough or misfiring.... It feels just like limp mode. But not a shake or anything weird like a driveline issue would feel.

[mpost]

I was thinking they might have mentioned it if there was something else.... haha. I'm taking that, and the doc you posted earlier talking about RPM during SLOW mode as evidence that what I'm experiencing is NOT limp/SLOW mode... considering that it happens with both of those switches disconnected. I'll confirm the check engine light next time out... when I turn the ignition on but don't start the boat in the driveway, the check engine light does not come on. Does that matter or mean anything? Someone mentioned that it should come on with the ignition.


Another point to make again is that it has been plugged into a computer at the shop and is not throwing any codes at all. Does that rule anything out? Would any of the ignition related stuff throw a code?

As stated earlier, the check engine light should come on with the ignition before the engine starts as there is no oil pressure. Page MT17 of the PCM book shows the same circuit for the GM engines as a Ford GT40.
The 5.7 APEX is a GM 350.
This definitely sounds like something other than limp mode for oil press or high temp.

[nyryan2001]

Only what feels like the engine running super rough or misfiring.... It feels just like limp mode.

and that’s exactly what happened when I had a cylinder misfiring.

If you have a misfiring cylinder... if you can find the plug, wire or cap/rotor causing the issue, it’s fixed instantly.

possibly replace the cap, rotor and just 4 plugs to start with... just change the plugs on one side. If it limps, swap those plugs to the other side.

To keep costs down... you could do cap, rotor, 4 plugs then test. Then add the other 4 plugs, then test. Then replace wires last.

[SoldTheBayliner]

It doesn't seem to care about engine temp as far as when it happens... lower RPMs certainly seems to make it happen though. But it's confusing me that it could just be something as simple as plugs or wires... if it was misfiring due to a bad plug or wire or something, wouldn't it just feel rough or miss at a certain RPM range and then correct itself as you backed off or advanced? (like a car would). What makes it decide "I will now run crappy until you shut me off and turn me back on."? That doesn't make any sense to me. That's why I assumed it was a limp mode thing.
Another bizarre twist is that the shop could not duplicate it on the trailer, only on the water. Just not testing it long enough at the right RPMs? or does it have to do with it being under load? I found a timing label on the engine, 10 before top dead center at 1000 RPMs. I will try to track down a light and confirm that's where we are.

I can only find an ignition coil for the 5.7 from 2002-up on nautiqueparts. I followed the coil wire from the distributor to the coil, and unplugged it at the coil end, and it's a little crusty in there... probably hasn't been off in 19 years, so not horrible considering that... I sent them an email, hoping to find the right part. The 2002-up one does look slightly different with the way the plugs go in.

So assuming the timing checks out... what would you guys do? standard tune-up stuff and hope I stumble on it? (plugs, wires, cap, rotor? ) Or jump right to the ignition coil?


^^ha, nyryan answered that while I was asking it...... Other input?

[SoldTheBayliner]

Another question: If it's a misfire due to bad plug, wire, or whatever... would that NOT show up when it was plugged into a computer at the shop? No code for that? When my car had a bad coil pack in one cylinder and you plug it into a code reader, it says "misfire cylinder #6"... not the case with these motors? The shop said there were no codes being thrown. $150 or so to throw new plugs, wires, and rotor cap on there. Totally willing to jump and do that, but I'm not confident because of the no code being thrown thing...

[Peter6000]

Another question: If it's a misfire due to bad plug, wire, or whatever... would that NOT show up when it was plugged into a computer at the shop? No code for that? When my car had a bad coil pack in one cylinder and you plug it into a code reader, it says "misfire cylinder #6"... not the case with these motors? The shop said there were no codes being thrown. $150 or so to throw new plugs, wires, and rotor cap on there. Totally willing to jump and do that, but I'm not confident because of the no code being thrown thing...

Can't really speak for the apex on the gt40 it would not it would only report sensor problems.

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