Odd jolt/odd RPM issue
Moderator: volvite
Odd jolt/odd RPM issue
I have a 2005 2WD, that at times while letting off the gas, I'll get a slight jolt. The RPMs will dip to about 600 and quickly jump to 1000 . If I lightly tap on the gas I get a slight bump or jolt. Seems like it only does this when it rainy outside or when the compressor is running. Never does it if the overdrive is turned off. Any ideas?
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HLEGuitars
- Posts: 22
- Joined: Thu Nov 28, 2013 2:50 pm
- Location: State College, PA
Ermugherd...
that could be a myriad of things...
however, my gut feeling is sensor or vac issue
My experience with the pathfinder is limited... however, I've been tuning injection for a while...
Problems that show up at changes in throttle are usually sensor or vac related..
you may no notice a vac leak under normal drving, but when you let off the throttle, the vac SHOULD go high immediately.. if there is a leak, this can be delayed.. the TPS can be showing say 5% but the vac reading can be higher in pressure (lower number) than expected for the given RPM, which would most likely cause a rich situation... then when you tap the throttle, the extra air leans out the mix
The A/C compressor puts more load on the engine, thus as you get off the gas, its going to want to die quicker..
I'm guessing that the RPM's stay a bit higher as you decel with the OD off..
Are you completely off the throttle when it happens, or easing up on it?
does it idle ok??
does it stumble if you blip the throttle?
that could be a myriad of things...
however, my gut feeling is sensor or vac issue
My experience with the pathfinder is limited... however, I've been tuning injection for a while...
Problems that show up at changes in throttle are usually sensor or vac related..
you may no notice a vac leak under normal drving, but when you let off the throttle, the vac SHOULD go high immediately.. if there is a leak, this can be delayed.. the TPS can be showing say 5% but the vac reading can be higher in pressure (lower number) than expected for the given RPM, which would most likely cause a rich situation... then when you tap the throttle, the extra air leans out the mix
The A/C compressor puts more load on the engine, thus as you get off the gas, its going to want to die quicker..
I'm guessing that the RPM's stay a bit higher as you decel with the OD off..
Are you completely off the throttle when it happens, or easing up on it?
does it idle ok??
does it stumble if you blip the throttle?
I've taken mine to the dealer about three times because of a similar problem -- although my RPMs are unaffected. Coasting at low speed (30-50 mph-ish), applying gas causes a thump as if the transmission is catching. Likewise, releasing the gas causes a similar disengagement thump.
The best way to describe it is to how a loose train car coupling reacts when the train speeds up or slows.
I've been told repeatedly by the dealerships that this is normal and there's no fix. I even printed out a TSB addressing something similar.
Our Pathfinder has so many little stupid annoyances and issues due to cheap, half-assed design that my wife and I have switched cars. She wouldn't care if the hood blew off on the highway and she fixes rattles by turning the radio up -- the perfect type of person for this car.
The best way to describe it is to how a loose train car coupling reacts when the train speeds up or slows.
I've been told repeatedly by the dealerships that this is normal and there's no fix. I even printed out a TSB addressing something similar.
Our Pathfinder has so many little stupid annoyances and issues due to cheap, half-assed design that my wife and I have switched cars. She wouldn't care if the hood blew off on the highway and she fixes rattles by turning the radio up -- the perfect type of person for this car.
Mine has made a somewhat similar noise/vibration since it was new but only if I'm abrupt with the go-pedal. Smoother transitions and it responds in kind.
I have a $55k Acura sitting here that does the same thing although it's more difficult to feather the throttle. I partially contribute it to these 5/6 speed transmissions which are just lugging along at those low speeds in the highest gear. When you make abrupt throttle changes at such a low rpm it just doesn't know what to do. My 6-speed Suburban does it a little as well.
I have a $55k Acura sitting here that does the same thing although it's more difficult to feather the throttle. I partially contribute it to these 5/6 speed transmissions which are just lugging along at those low speeds in the highest gear. When you make abrupt throttle changes at such a low rpm it just doesn't know what to do. My 6-speed Suburban does it a little as well.
I know what you're talking about and mine does that, too. The transmission freaks out for a second and doesn't know whether to up shift, down shift or stay.
The bump is something different, though, I think. Mine bumps no matter how smoothly I feather the gas pedal. Say you're accelerating casually down a straight, level road (that's where it's most noticeable). You reach 45mph and release the pedal to coast. At the point where the transmission disengages to coast, it bumps about one second after you release the pedal. So it's like this: release... one second pause... bump.
Then, you casually apply the gas again and, at the point of the transmission engaging, there's the bump again. It's as if the gears in the transmission don't fit tightly. Like there's space between the teeth or something. Or like you're pulling a trailer that has a 4" receiver with a hitch that has a 2" ball.
It's like the more you try to avoid the bump, the more it bumps.
The bump is something different, though, I think. Mine bumps no matter how smoothly I feather the gas pedal. Say you're accelerating casually down a straight, level road (that's where it's most noticeable). You reach 45mph and release the pedal to coast. At the point where the transmission disengages to coast, it bumps about one second after you release the pedal. So it's like this: release... one second pause... bump.
Then, you casually apply the gas again and, at the point of the transmission engaging, there's the bump again. It's as if the gears in the transmission don't fit tightly. Like there's space between the teeth or something. Or like you're pulling a trailer that has a 4" receiver with a hitch that has a 2" ball.
It's like the more you try to avoid the bump, the more it bumps.
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HLEGuitars
- Posts: 22
- Joined: Thu Nov 28, 2013 2:50 pm
- Location: State College, PA
after these descriptions...
I'm starting to agree that this is mechanical in the drivetrain and not related to fuel management / sensor issues.
Have your checked the universal joints on the drive shaft??
what i'm getting is that when there is a slight negative load on the drivetrain followed by a zero load and then a slight positive load.. you are having a "bump"
With OD disengaged, the engine will be dragging a bit more, putting more negative load for a longer time, thus when you hit the gas again, the slack is taken up quicker and, while the bump is probably still there, its not as noticeable....
this tells me that something has play in it.. drive shaft, rear diff, internal transmission, something
I'm starting to agree that this is mechanical in the drivetrain and not related to fuel management / sensor issues.
Have your checked the universal joints on the drive shaft??
what i'm getting is that when there is a slight negative load on the drivetrain followed by a zero load and then a slight positive load.. you are having a "bump"
With OD disengaged, the engine will be dragging a bit more, putting more negative load for a longer time, thus when you hit the gas again, the slack is taken up quicker and, while the bump is probably still there, its not as noticeable....
this tells me that something has play in it.. drive shaft, rear diff, internal transmission, something
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