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Old 06-19-2019, 08:33 AM
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tjrowbot tjrowbot is offline
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Navigator Engine - RPM Issue? Cause?

Looking for any ideas what may be happening / caused an issue on my 11’ Navigator. Some mornings when leaving for work it seems like it has a delayed reaction shifting from first to second (higher RPM’s) and then when it does shift the RPM drop to about 1k. Nothing major, but there also seems to have a low groan noise from what I think is the engine running at such a low RPM.

Here is the scary issue: driving home with the family we were traveling at 55mph on a two lane highway close to home, flat road. What I remember happening was I let off the accelerator the RPM’s dropped to 1k, then spiked to 4k, there was a “clunk”, RPM’s went back to normal, spiked again, another “clunk”, then the rear tires locked for a micro-second and skipped twice. I shifted to neutral and coasted to the shoulder. This happened in all of 5 seconds. The engine shut down throwing a code. I limped it home one mile not knowing what happened and ultimately thinking it was the transmission. I used my scanner, but I passed on my older reader.

I drove it 10 miles to our mechanic who we trust and it drove fine. He cleared the code (and I have not received the code yet so I cannot investigate). He drove it three different times and said that he could not diagnose the issue and did not want to tear apart the tranny as the issue did not point to a transmission.

What are your thoughts on this issue? I basically think that for some reason when traveling 45-60mph, when I let off the accelerator the RPM’s want to drop too low, this causes the engine to “skip” or be underpowered which caused the locking of the rear axle. As you can tell, I am no mechanic and am struggling putting the right words into the issue. Any help would be appreciated as I do not want to put my family in any danger. Thank you in advance, Tyler.
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Old 06-19-2019, 09:05 AM
CrashCourse316 CrashCourse316 is online now
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Quote:
Originally Posted by tjrowbot View Post
Looking for any ideas what may be happening / caused an issue on my 11’ Navigator. Some mornings when leaving for work it seems like it has a delayed reaction shifting from first to second (higher RPM’s) and then when it does shift the RPM drop to about 1k. Nothing major, but there also seems to have a low groan noise from what I think is the engine running at such a low RPM.

Here is the scary issue: driving home with the family we were traveling at 55mph on a two lane highway close to home, flat road. What I remember happening was I let off the accelerator the RPM’s dropped to 1k, then spiked to 4k, there was a “clunk”, RPM’s went back to normal, spiked again, another “clunk”, then the rear tires locked for a micro-second and skipped twice. I shifted to neutral and coasted to the shoulder. This happened in all of 5 seconds. The engine shut down throwing a code. I limped it home one mile not knowing what happened and ultimately thinking it was the transmission. I used my scanner, but I passed on my older reader.

I drove it 10 miles to our mechanic who we trust and it drove fine. He cleared the code (and I have not received the code yet so I cannot investigate). He drove it three different times and said that he could not diagnose the issue and did not want to tear apart the tranny as the issue did not point to a transmission.

What are your thoughts on this issue? I basically think that for some reason when traveling 45-60mph, when I let off the accelerator the RPM’s want to drop too low, this causes the engine to “skip” or be underpowered which caused the locking of the rear axle. As you can tell, I am no mechanic and am struggling putting the right words into the issue. Any help would be appreciated as I do not want to put my family in any danger. Thank you in advance, Tyler.
If you turn off your car while in gear the mechanical aspect of it should not lock up the tires. Not it is not exactly like in neutral since you are in gear and the resistance from that will slow the car down faster but it shouldn't lock up. If the car when to shift to a lower gear for no apparent reason it could feel like the tires locked while the RPM was to low since it has to use the tires to bring up the RPM instead of the engine. If it sounded like your car RPM did not change and your tired just gave a lockup squeal for a fraction of a second then went back to normal after no RPM change then you probably had the trans pull a quick shift in confusion.

Not that you haven't already investigated it but have you checked and changed your transmission fluid?

feel if it has a grit to it or if it smells more burnt than like trans fluid you probably have an issue you wont solve by yourself. A lot of the slipping clunking and wierd stuff could be cause by a lot of things from low or bad trans fluid, leaking seals internal or external, bad gearing that's worn out, or it could just be an electrical problem. It's possible your 1st to second gear is actually a 1st to 3rd gear shift based on your description of dropping to a low 1k rpm after being higher rpm in first gear. Count your gear shifts all the way to your highest gear when getting going. you might find your short one.

Does your car feel like it vibrates during acceleration and then stops when coasting?
does it drop to neutral ever without you putting it there?
does the trans slip at all like car revs a little then clunks into gear?


That in mind. we are home boat mechanics. we don't normally deal with gears and tires....
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Old 06-19-2019, 09:46 AM
BudmanV24 BudmanV24 is offline
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This sounds like the issue that was affecting the f150s. I believe there was a recall.
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Old 06-19-2019, 11:58 AM
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That is the frustrating part of the issue, it drives really nice, no vibration whatsoever, shifts smooth, stays in gear (thank goodness), no slipping of the trans, or anything.

It did feel like it may have dropped a gear then back into the gear. I am not saying I am happy with the outcome, but a confused shift my have been the issue. Trans fluid did not have a burned smell or grit, but I am going to swing by someone who knows more about that type of stuff later today.
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Old 06-19-2019, 02:10 PM
CrashCourse316 CrashCourse316 is online now
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Originally Posted by tjrowbot View Post
That is the frustrating part of the issue, it drives really nice, no vibration whatsoever, shifts smooth, stays in gear (thank goodness), no slipping of the trans, or anything.

It did feel like it may have dropped a gear then back into the gear. I am not saying I am happy with the outcome, but a confused shift my have been the issue. Trans fluid did not have a burned smell or grit, but I am going to swing by someone who knows more about that type of stuff later today.
My guess is confused computer, may need a reset or fix if it continues but i'm just guessing. Best bet is what your doing, taking to someone who knows stuff.
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Old 06-19-2019, 02:28 PM
Razzys Wagon Razzys Wagon is offline
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All the shift strategies are load based, if it gets a funky input from the pcm to the tcm(garbage in, garbage out) it will wig out and not know what to do, so it hunts until it finds what it needs or acts stupid and throws a light. How to fix this, well, all the others i have dealt with, mostly explorers and such, they just needed a good old fashion tune up. These 100k spark plugs start getting a really wide gap around 50k, so the pcm starts adjusting the load tables to compensate, so as you get more miles in, it starts getting real close to the outer limits of adjustment in the load tables and boom, it spits out a number the TCM gets confused with and you have a problem like your having.
i dont know the miles or when you did a plug change last, but it fixed the last 6 that were having problems close to yours.

i put new plugs in, and cleaned the MAF sensor with electronics cleaner, reinstalled it and reset the KAM on the pcm. if your scan tool wont reset the KAM, just pull the cables off the battery and touch the 2 cables ends together to drain the capacitors in the pcm and let sit over night. reconnect in the am and drive normally.
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Old 06-20-2019, 09:10 AM
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Thank you for the explanation and I will use this information. It sounds like a good old fashion tune up will be the starting point. For the record, the Navi has about 85k on it. Thank you all for the input.
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Old 06-20-2019, 10:56 AM
Razzys Wagon Razzys Wagon is offline
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post back if this helps it so i can keep notes.

Thanks!

i own NC Speed Lab and i like to keep up with these type of things...lol
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