sc89 Posted December 9, 2011 Share Posted December 9, 2011 I have a 1998 pathfinder, SE..with 123,000 miles/200,000 kilometers. Can someone explain to me why when I'm on the highway, I put my truck into cruise control..at any speed really..50-75mph or 80-120kmh..and the rpm's will settle at the normal level..then say randomly, it will go up..then back to normal..then back up..back to normal..it's almost as if it's "fishing" or "searching" for the right gear..which I guess would make sense at speeds maybe closer to when 4th gear would switch into 3rd. This is really weird and I'm worried. For the record, the transmission fluid has been drained and refilled roughly every 25,000miles/40,000km..since I had the vehicle at 85,000miles/143,000km. Thanks in advance, as I am worried..I will be checking this thread often! Link to comment Share on other sites More sharing options...
Reshma Posted December 9, 2011 Share Posted December 9, 2011 Gotta be more specific. Sounds like she's just trying to keep the cruise speed set. A little rev here and there aint too bad. IDK tho thats just my ima noob. Link to comment Share on other sites More sharing options...
sc89 Posted December 9, 2011 Author Share Posted December 9, 2011 I guess I should mention that it hunts up and down on the RPM's without any factors changing..such as the inclination or anything.. Link to comment Share on other sites More sharing options...
MY1PATH Posted December 9, 2011 Share Posted December 9, 2011 First thing I would check is that hose coming out of the back of your cruise control going to the cruise vacuum pump. Link to comment Share on other sites More sharing options...
pathfounder Posted December 10, 2011 Share Posted December 10, 2011 (edited) If it's only going up by a couple hundred RPM, it's the torque converter clutch releasing and engaging. It will do this to give the gutless engine under the hood a fighting chance at getting through a gust of wind or small hill. Mine did it often with or without using cruise control, especially when I put the 31s on. You could confirm this by driving a bit slower and seeing if it goes away, or way faster. Best remedy is probably a V8 swap. Edited December 10, 2011 by pathfounder Link to comment Share on other sites More sharing options...
1994SEV6 Posted December 10, 2011 Share Posted December 10, 2011 Best remedy is probably a V8 swap. LOL I see what you did there. Very clever. Is it just the needle or is the engine actually increasing RPM? Can you hear/feel it? I guess, what I'm asking is if it's actually happening, or if JUST a needle says so? The needle could be faulty. Link to comment Share on other sites More sharing options...
Kingman Posted December 10, 2011 Share Posted December 10, 2011 Sounds like it's the torque converter locking/unlocking if the revs go up a bit and back down. They all do it. No big deal. If it's actually downshifting and hunting, that's different. Link to comment Share on other sites More sharing options...
adamzan Posted December 10, 2011 Share Posted December 10, 2011 If it's only going up by a couple hundred RPM, it's the torque converter clutch releasing and engaging. It will do this to give the gutless engine under the hood a fighting chance at getting through a gust of wind or small hill. Mine did it often with or without using cruise control, especially when I put the 31s on. You could confirm this by driving a bit slower and seeing if it goes away, or way faster. Best remedy is probably a V8 swap. C'mon, in an r50 its not THAT bad . Want to take my 3.0 for a ride with the 33" tires?? Link to comment Share on other sites More sharing options...
sc89 Posted December 11, 2011 Author Share Posted December 11, 2011 If it's only going up by a couple hundred RPM, it's the torque converter clutch releasing and engaging. It will do this to give the gutless engine under the hood a fighting chance at getting through a gust of wind or small hill. Yeah, it could be that. Lately we have been getting some wind here, but nothing too serious. I've noticed that it's doing it more often when I'm going against the wind, so possibly that's it. As well, the RPM's are going up (or down, it's weird), from 200RPM<x<500RPM Is it just the needle or is the engine actually increasing RPM? Can you hear/feel it? I guess, what I'm asking is if it's actually happening, or if JUST a needle says so? The needle could be faulty. Yeah I can hear it and feel it, through the seats. It's as if the vehicle is jerking a little bit when it goes "up and down", the RPMs. Sounds like it's the torque converter locking/unlocking if the revs go up a bit and back down. They all do it. No big deal. If it's actually downshifting and hunting, that's different. This whole RPM's "randomly" going up and down feels weird because I can feel it through the seat. However, I don't think it's actually down shifting because when the RPMs go down, I tried stepping on the gas..and when I did that the car just advanced without changing gears. The truck is an automatic, you probably know this, but you would know when it changes gears, through the RPMs and you can feel it. So I don't think it's actually downshifting. However, if I put cruise control on and cruise at a low speed (I was testing to see how good of MPG I could get)..this was before this whole weird "problem" (maybe it's just happening now because of the wind we have been getting and I'm over reacting), if I'm going say 48-50mph on cruise..and I go down a hill..the RPMs drop by about 300-500..and it feels as if it wants to downshift. Link to comment Share on other sites More sharing options...
pathfounder Posted December 12, 2011 Share Posted December 12, 2011 Based on your last post, it sounds like it's either not a problem, or the converter clutch could be acting up. It does happen. I've had one stick engaged right until the engine got to 0rpm. I've also had one engage and disengage really abruptly on flat ground and steady speed for no reason. They do fail sometimes. If the RPM change is very small and it feels like half of a real gear change, or the opposite, feeling like you've been rear-ended, then it could very well be the clutch. Link to comment Share on other sites More sharing options...
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