Surges In Power While Lifting Off Throttle
01-19-2005, 01:51 AM
#1
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Surges In Power While Lifting Off Throttle
Hey guys, I'm new here and I'm looking for some veteran help. I sold my rsx-s nearly a month ago and have been searching for an S2000. I've driven a few now and yesterday I almost bought an 03 N.F.Red with 8k miles but one thing was holding me back. During the test drive I felt some hiccups in the power delivery. I've spent quite a bit of time searching the forum but haven't come across any posts with symptoms similar to mine.
It seemed odd how it was happening, the power seemed smooth when I was on the throttle but then if I'd slowly lift off the throttle I'd feel little surges of power. I didn't record the exact engine speed, speed, ect. when it happened - but it was in like 2nd and 3rd gear, if I'd accelerate at a moderate pace up to 4-5k rpm then hold it there briefly and then slowly lift off the throttle I'd get the surges. I've been driving stick for a long time and it wasn't the normal bucking like you can easily get in 1st gear at parking lot speeds - this was a little different.
I thought maybe it was just the nature of the car, or because it was cold outside but I wasn't sure so I didn't buy it. I loved every other detail about the car and the condition it was in. Anyone else experience a problem like this?
Thanks -Joe
It seemed odd how it was happening, the power seemed smooth when I was on the throttle but then if I'd slowly lift off the throttle I'd feel little surges of power. I didn't record the exact engine speed, speed, ect. when it happened - but it was in like 2nd and 3rd gear, if I'd accelerate at a moderate pace up to 4-5k rpm then hold it there briefly and then slowly lift off the throttle I'd get the surges. I've been driving stick for a long time and it wasn't the normal bucking like you can easily get in 1st gear at parking lot speeds - this was a little different.
I thought maybe it was just the nature of the car, or because it was cold outside but I wasn't sure so I didn't buy it. I loved every other detail about the car and the condition it was in. Anyone else experience a problem like this?
Thanks -Joe
10-01-2005, 03:54 PM
#3
I have been noticing similar behavior with my 00. This is my 2nd S2000 and it was not an issue with the first so we can rule out driver error 
I can not for the life of me ease on or off the throttle gently enough to prevent jerk. (FYI, I have about 3-4 years of track driving under my belt. You need SMOOTH throttle input with this car on the track, especially in the rain and this problem has caused some unwanted oversteer from time to time
)
To simulate what I feel, get on the throttle and lift immediately. You feel the inertia and slack in the driveline kick back at you. Same as if you were to pump the throttle while at a moderate speed. You can make it oscillate (jerk).
It's annoying as hell. I have adjusted my cable, installed a new filter (stock air box). Whacked my MAP, I have yet to install new plugs and clean up my PVC though.
I am beginning to think I have too much slack in my driveline. Possibly the inner CV's are wearing, although I do not have any shakes at speed.
Does anyone know how to measure slack in the drive train? I.E. how much you should be able to rotate your driveshaft while the e-brake is engaged? I have noticed more jerks when starting off. Hook up doesn't feel as solid as it once did. Feels like the drive shaft as a bit of spring in it.
I can not for the life of me ease on or off the throttle gently enough to prevent jerk. (FYI, I have about 3-4 years of track driving under my belt. You need SMOOTH throttle input with this car on the track, especially in the rain and this problem has caused some unwanted oversteer from time to time
)To simulate what I feel, get on the throttle and lift immediately. You feel the inertia and slack in the driveline kick back at you. Same as if you were to pump the throttle while at a moderate speed. You can make it oscillate (jerk).
It's annoying as hell. I have adjusted my cable, installed a new filter (stock air box). Whacked my MAP, I have yet to install new plugs and clean up my PVC though.
I am beginning to think I have too much slack in my driveline. Possibly the inner CV's are wearing, although I do not have any shakes at speed.
Does anyone know how to measure slack in the drive train? I.E. how much you should be able to rotate your driveshaft while the e-brake is engaged? I have noticed more jerks when starting off. Hook up doesn't feel as solid as it once did. Feels like the drive shaft as a bit of spring in it.
10-01-2005, 04:14 PM
#4
I would suggest you make sure the throttle cable slack is what it's supposed to be. The bare part at the throttle plate should have about 1/4" up and down movement in the middle of the bare cable.
Also, surging while lifting throttle may be an indication of some cable binding in the sheath. I suggest that you disconnect the cable from the throttle body and test it by pulling it out and pushing it back in. Is it sluggish? Is it binding in any way? Does it seem to catch? If so, pull it as far out as you can, take a spray can of silicone with the little straw and shoot a good amount down the sheath. Then work the cable in and out and use more silicone if it begins to loosen up. The cable assembly may have drawn in dirt and grit and where the cable loops around, this grunge may be inhibiting cable movement. Also, while you're at it, silicone any of the pivot points on the throttle plate actuation mechanism (the part the cable attaches to) and work the mechanism by hand to get the silicone in there.
You can control increasing throttle OK because you are using foot strength. However, closing throttle is dependent upon the throttle plate return spring and this may not be strong enough to fight any binding that may be present.
Also, surging while lifting throttle may be an indication of some cable binding in the sheath. I suggest that you disconnect the cable from the throttle body and test it by pulling it out and pushing it back in. Is it sluggish? Is it binding in any way? Does it seem to catch? If so, pull it as far out as you can, take a spray can of silicone with the little straw and shoot a good amount down the sheath. Then work the cable in and out and use more silicone if it begins to loosen up. The cable assembly may have drawn in dirt and grit and where the cable loops around, this grunge may be inhibiting cable movement. Also, while you're at it, silicone any of the pivot points on the throttle plate actuation mechanism (the part the cable attaches to) and work the mechanism by hand to get the silicone in there.
You can control increasing throttle OK because you are using foot strength. However, closing throttle is dependent upon the throttle plate return spring and this may not be strong enough to fight any binding that may be present.
10-01-2005, 04:56 PM
#5
I have had some "bucking" at very slow parking lot speeds in 1st gear when I lift off the throttle, I just input some clutch and all is fine. This has only ever happened at speeds under 10 km/h and I think only twice.
10-01-2005, 05:00 PM
#6
It's the same for acel and decel though, it's not just decel. The throttle is adjusted properley, and there is 0 resistance through the pedal, however i will have a look at it.
This doesn't feel like a throttle pedal/cable problem. But I will lube it and see if it elimates anything. It feels like i have too much slack in the drivetrain form the transmission back (diff, cv in and out).
If i were to put it in words. It feels like i have a hard rubber driveshaft that allows some for some torsion.
This doesn't feel like a throttle pedal/cable problem. But I will lube it and see if it elimates anything. It feels like i have too much slack in the drivetrain form the transmission back (diff, cv in and out).
If i were to put it in words. It feels like i have a hard rubber driveshaft that allows some for some torsion.
10-01-2005, 05:19 PM
#7
Originally Posted by LUV2REV,Oct 1 2005, 08:56 PM
I have had some "bucking" at very slow parking lot speeds in 1st gear when I lift off the throttle, I just input some clutch and all is fine. This has only ever happened at speeds under 10 km/h and I think only twice.
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10-01-2005, 05:22 PM
#8
Originally Posted by Jasonoff,Oct 1 2005, 07:00 PM
It's the same for acel and decel though, it's not just decel. The throttle is adjusted properley, and there is 0 resistance through the pedal, however i will have a look at it.
This doesn't feel like a throttle pedal/cable problem. But I will lube it and see if it elimates anything. It feels like i have too much slack in the drivetrain form the transmission back (diff, cv in and out).
If i were to put it in words. It feels like i have a hard rubber driveshaft that allows some for some torsion.
This doesn't feel like a throttle pedal/cable problem. But I will lube it and see if it elimates anything. It feels like i have too much slack in the drivetrain form the transmission back (diff, cv in and out).
If i were to put it in words. It feels like i have a hard rubber driveshaft that allows some for some torsion.
Can you eliminate driveline lash? That is, when you go from accel to decel, is there is kind of noticeable lurch? And when you go from decel to accel, is there the same sort of lurch? This may mean that all the little spaces between gear teeth in the tranny, rear diff have gotten worn and bigger.
Or are you saying that it's more than just one single lurch, that the accel or decel is rhythmically "lunging"? If this is more the case, then Sideway's post bears looking into. The throttle position may need to be re-learned. Also, it could be a MAP issue (or MAP wiring harness securing issue).
10-01-2005, 05:31 PM
#9
"Can you eliminate driveline lash? That is, when you go from accel to decel, is there is kind of noticeable lurch? And when you go from decel to accel, is there the same sort of lurch?"
That's what I feel. The car yoings (best made up word i could think of) when you apply or let off on the throttle. It was much worse before i adjusted the cable and replaced the filter but that didn't solve it completely.
It feels as if i have play in the driveline. from how it feels it's not tranny related, but that's my opinion. I'm willing to bet a nut it's something after the transmission.
That's what I feel. The car yoings (best made up word i could think of) when you apply or let off on the throttle. It was much worse before i adjusted the cable and replaced the filter but that didn't solve it completely.
It feels as if i have play in the driveline. from how it feels it's not tranny related, but that's my opinion. I'm willing to bet a nut it's something after the transmission.
10-01-2005, 05:40 PM
#10
Originally Posted by Jasonoff,Oct 1 2005, 07:31 PM
I'm willing to bet a nut it's something after the transmission.
You "might" be right but remember, ALL those little spaces throughout the drivetrain, from the engine right on back to the rear 1/2 shafts contribute to this lash.