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Having trouble at freeway speeds
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tractorboy
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May 5, 2024, 6:19 PM
Post #1 of 18
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Having trouble at freeway speeds
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It's a 2002 Nissan Sentra 1.8L Automatic transmission. i am posting this here because i believe it's the transmission for the simple fact whatever is happening the car computer does not know it's happening. The car starts great, idles and runs well. gets great gas milage. The car has about 196k miles, uses no oil, well lol nothing to complain about. Accelerates great. at around 60+ mph when cruising at a set speed the car will start bucking. I thought it was a misfire but I am not getting a CEL stating a misfire so ...?
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Hammer Time
Ultimate Carjunky
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May 5, 2024, 6:46 PM
Post #2 of 18
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Re: Having trouble at freeway speeds
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It doesn't mean anything that you aren't getting a code. It has to see repeats of the misfire to set the code.. If you drive it long enough it may set a code.
It could also be the TCC solenoid cutting in and out. You can check that by shutting off overdrive to see if it stops.
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tractorboy
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May 6, 2024, 5:35 AM
Post #3 of 18
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Re: Having trouble at freeway speeds
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oh I drove it far enough to set a code. about a year ago i bought some name brand plugs on Ebay which I now think were cheap knock offs b/c the car would do basically / sort off the same thing but i would get a CEL really quick and it was not a misfire code it was another code , can't remember but it was sort of saying the ignition as a whole was at fault.
If I put the old plugs back in and cleared the CEL all was good again. I will try that so yeah being the TCC solenoid.
so how does the ECM know there is a misfire. Computers live in the Millisecond world...lol I was thinking the car computer looks at each exhaust puff from each cylinder with the Ox sensor and knows what should be there and/ or the same for the crank shaft sensor does not see that "push" from the offending cylinder on the timing fence. I know the Impala I had had a timing fence on the back of the crank shaft dampener not sure if the sentra has that or just a few holes drilled in the crank shaft 90° or so. The crankshaft sensor for the Sentra is not at either end of the crankshaft somewhere along the length. Another reason I think it is the transmission is, usually at about 60mph i am at about 2.5k RPMs.... so the motor does not know if i am going 25mph at 2.5k rpm in second gear or at 6omph at 2.5k rpm, where the misfire would happen across the full spectrum of RPM
(This post was edited by tractorboy on May 6, 2024, 5:47 AM)
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Hammer Time
Ultimate Carjunky
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May 6, 2024, 6:12 AM
Post #4 of 18
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Re: Having trouble at freeway speeds
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The computer sees misfires through the speed of the crankshaft using the crank sensor.
The reason you may not see a code is because the computer doesn't set a code as soon as it sees a misfire. It looks for a pattern so it doesn't set a false code.
I have seen many misfires that were caused by a faulty fuel injector never set a code because the speed change never meets the criteria for setting a code.
It still may be a torque converter problem because of the specific speed it is occurring.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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tractorboy
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May 6, 2024, 6:45 AM
Post #5 of 18
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Re: Having trouble at freeway speeds
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I will try switching off the OD ( TCC) and see if that is the issue. yeah the Impala I had had a 4T65E Transmission that had solenoid issues, can't remember what solenoid it was , GM called it the "force motor" what was happening was it was leaking fluid past so the BCM or PCM would command the pump at a higher rate to keep the transmission clutch plates from burning so it would cause really harsh shifts, to get to the solenoid had to wither pull the transmission or drop the engine cradle enough to get the side cover off. I ended up donating the car to charity b/c the jack points on one side were completely rusted out and probably would not pass the state inspection. i really liked the car though. Had split bench seats, rode really nice to down the road.. also had an idle surge issue...tracked it down to the knock sensor..
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tractorboy
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May 8, 2024, 6:24 AM
Post #6 of 18
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Re: Having trouble at freeway speeds
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Sentra drives fine at freeway speeds with the OD off. RPMs are about 1.5k higher as expected. If it's the TCC solenoid, why I am not getting a CEL? I suppose the solenoid can fail in a way that to the TCM it still looks good? Or could it be something else mechanically with the transmission? Was wondering too could it be the transmission fluid? I have never changed the transmission fluid since I have had the car and not sure if the past owners did any changes.
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Hammer Time
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May 8, 2024, 6:30 AM
Post #7 of 18
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Re: Having trouble at freeway speeds
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You have to realize the computer is not a "catch all" for problems. MANY issues will not set a code. The solenoid could be the problem but it's not the only possibility. I would try replacing the solenoid first if it's accessible.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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tractorboy
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May 8, 2024, 7:29 PM
Post #8 of 18
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Re: Having trouble at freeway speeds
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oh I agree with that.....i have to say though that the cars i have had that had an ECM or PCM they were pretty much there telling me there was an issue either before or when the car was doing whatever....yes, scanners are just a tool. I think a lot of people rely on the scanner telling them what to do....like that issue I had with my Impala, the idle surge, it set no code, same for the harsh shifts.
OK will change out the solenoid looking now for it's location.
(This post was edited by tractorboy on May 8, 2024, 7:32 PM)
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Hammer Time
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May 8, 2024, 7:32 PM
Post #9 of 18
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Re: Having trouble at freeway speeds
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Computers only monitor what they were programmed to look at.
It looks like all the solenoids are packaged together as one unit attached to the valve body.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on May 8, 2024, 7:49 PM)
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tractorboy
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May 9, 2024, 10:46 AM
Post #10 of 18
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Re: Having trouble at freeway speeds
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ok thanks HT. i assume u have access to ALL DATA? lol . The valve body, that is what I look at when i drop the transmission oil pan?
so I am thinking that the whole bank of solenoids can be removed w/o removing the valve body? Just looked RockAuto has the solenoids and so does NAPA, they have some on Ebay that say new then in the description say refurb, though they are about 1/6 the price of the new.
what sensor detects what gear the transmission is in?
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Hammer Time
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May 9, 2024, 11:24 AM
Post #11 of 18
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Re: Having trouble at freeway speeds
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The valve body determines the gear but overdrive is not a separate gear. It locks up the torque converter to eliminate all slippage for the higher gear.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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tractorboy
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May 10, 2024, 7:45 AM
Post #12 of 18
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Re: Having trouble at freeway speeds
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to my understanding, the torque converter locks up for OD when 3 tasks happen. 1. transmission speed 2. transmission fluid temp and 3 the transmission was in 4th gear....... was wondering if the TCM/PCM was getting an intermittent signal like 3rd gear, no wait 4th gear no wait 3rd gear again lol and the TCM was commanding the solenoid to follow?
i have no idea  just trying to examine all possibilities, but yes right now the actual solenoid does seem the most likely and doing a refresh of all the solenoids too...... is just dropping the transmission oil pan all i need to do to replace the solenoids from the valve control body. new pan gasket, solenoids fluid and filter ? no removal of the valve control body?
(This post was edited by tractorboy on May 10, 2024, 7:47 AM)
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Hammer Time
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May 10, 2024, 7:53 AM
Post #13 of 18
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Re: Having trouble at freeway speeds
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I tried to enlarge it but the site wouldn't allow it.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on May 10, 2024, 7:58 AM)
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tractorboy
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May 10, 2024, 5:29 PM
Post #14 of 18
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Re: Having trouble at freeway speeds
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yeah, thanks, so looks like i do need to remove the valve body
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tractorboy
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May 11, 2024, 10:36 AM
Post #15 of 18
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Re: Having trouble at freeway speeds
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does the CEL come on for emission fault codes only?
anyway. I drove the Sentra on the freeway today with the OD on and it seems to be ok. maybe some crud in the valve body or TCC that was dislodged by driving without the OD on
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Hammer Time
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May 11, 2024, 10:39 AM
Post #16 of 18
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Re: Having trouble at freeway speeds
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It comes on for situations it was programmed to monitor.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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May 11, 2024, 12:17 PM
Post #18 of 18
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Re: Having trouble at freeway speeds
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Factory engineers determine what the computer monitors and it's not just emissions. It's whatever the factory determines to require monitoring. All the various computers monitor all aspects of the vehicle including body functions.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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