cobra21

iTrader: (7)

is it normal in the 5.5 gens that when you are driving and let off the gas that you get somewhat of a buck in each gear. i understand that it is a manual and its not going to be smooth like an auto. but it seems to buck more than usual in its own degree in each gear.

kenshi

Has it always happened or recent? Clutch slipping? When you downshift, ideally you want to match revs so you don't use your clutch as a brake. If you don't do that, you're going to wear it out faster.

cobra21

iTrader: (7)

no no...it doesnt have to do with matching revs or driving stick. i meant to clarify this before i left work. when in each gear, and i hit the gas and let off. nothing to do with shifting, just being in the gear and letting off it appears to buck more so than any other car that i have driven. is it a problem or is it just in my head?

kenshi

Sorry. I misunderstood. You're saying that when you're in any gear, more noticeable in lower gears, when you accelerate you get a bit of a jerk and when you decellerate you also get a bit of a jerk?

Do you see your tachometer change quickly corresponding to what you feel? Like when you press the gas, does the tach jump up then go back a bit?

LA02MAX

iTrader: (3)

Mine does this as well. My guess: Soft motor/tranny mounts + lots of low-end torque + short gears. If you notice, it doesn't do it as bad in the higher gears. This is because the torque multiplication is much less...Mine has gotten worse since I've had my car, and since my motor mounts have about had it (going to install my ES Polyurethene MMs next weekend) I'm guessing that's a big contributing factor. I'll let you know how it is once those are installed, but otherwise it's pretty normal...

kenshi

^^^ Very good point. Motor mounts can give you exactly that problem.

cobra21

iTrader: (7)

thats true it tends to go away in the higher gears. more noticeable at low gears. i mean my car only has 40k on it. im not sure my motor mounts are done. ok so i guess i wont worry about it. im used to other manual cars where you dont feel the jerk as much. thanks guys

P. Samson

This could be caused by an incorrect idle problem probably caused by the TB. It's not the mounts.

kenshi

And how would an idle problem cause a symptom that only happens while not idling, but at speed and in gear?

AE-Max

i have a 01 maxima 5 spd, and it does the same thing, haven't noticed it much when i got the car but now you definitely notice it. its getting annoying as hell.

LA02MAX

iTrader: (3)

The Electronic throttle is fairly sensitive, but I doubt it's the cause. It's been doing it in my car for a long time and it even does it in cars that have a cable throttle (older accord, jetta, and even maximas) just some cars are more pronounced than others. The mounts are a viable explanation. Just look at the shifter and you can see it rocking back and forth when it happens.

cobra21

iTrader: (7)

yea my shifter moves a little bit when i let off the gas. so the mounts explains that?

P. Samson

It can be a basic "idle" issue because he's talking about the throttle being CLOSED, which with the clutch engaged does not necessarily mean idle RPM. Closed throttle hunting, jerking, bucking, and slow engine deceleration on shifting are all signs of possible basic idle issues, whether it's a fly by wire TB (Gen. 5.5) or the IACV idle control system on the earlier cars. On his Gen. 5.5 I would check the TB for crud around the throttle plate, clean as necessary, check the throttle actuator for operation, and do an Idle Air Volume Learn.

LA02MAX

iTrader: (3)

I know what you are saying, but I have had this issue for 35k miles. As it's happening, the RPMs are not oscillating and the needle is falling linearly as usual and the engine could be at 4k rpms and falling and it will still do the same thing. The faster you let go of the throttle and the lower the gear, the more it does it. If that weren't the case, I could be in 4th gear at 25 mph and it would do the same thing if I released the gas pedal quickly. I just cleaned my throttle body and did the ECU reset/IAVL this past weekend and although my idle is a bit higher (it's been low for the past couple of months) nothing else has changed. Also, if the throttle body were at fault, nearly every manual car I've driven would also have a messed up TB and what are the chances in that?

P. Samson

If you are decelerating with closed throttle, in gear, with the clutch engaged I doubt that you will see the tach. show any "fluctuations", (it will obviously "follow" the speed decrease)....... you'll just feel it. And it probably will be more noticeable in the lower gears. Is your warm, no load idle absolutely stable and 625 +/- 50 RPM? Obtaining a stable and correct idle on these cars is critical ........and assuming that there are no other problems, it is an indication (proof) that the basic adjustments/checks such as the Closed Throttle Pos. Learn, the IAVL are "learned", the ignition timing is correct and therefore the idle A/F ratio is correct. Do you feel any jerking or hunting when you are cruising on the highway at a steady speed?

LA02MAX

iTrader: (3)

Good lord I was tired Waking up from a nap FTL. Let me try that again....

Description of the issue at hand:

-Say you're in first gear, cruising along in traffic at 5-10 mph. You let go of the gas and for a second, the car rocks back and forth, but the RPMs do not oscillate. The velocity of the RPM needle falls very linearly with vehicle speed.
-It does not have to be first gear, but the lower the gear the problem typically is worse.
-Doesn't matter the engine speed. You can be at 1500 RPMs or 5000 and it'll still do the same thing.
-Like I said before, the torque multiplication in the first two gears is MUCH higher than that of the latter gears.

Possible Culprits:

A.) Throttle Body - The throttle body could be sticking resulting in a sporatic poisition of the butterfly valve.
If this were the case, there would be more problems than just the issue at hand. It wouldn't be dependent on what gear you are in (ie: you could be doing 20mph in 4th gear and it would do the same thing, which it doesn't). The throttle sticking would cause issues at idle (like you mentioned) and initial movement of the TB plate would be jumpy giving you a hard time to take off smoothly. None of those issues apply.

My car has been doing the same thing for about 30k miles, albeit a little worse lately. For the past 6 months or so, my car has had a low idle (~450) and I have completed the ECU reset/IAVL/accelerator pedal position, etc. procedures several times with no help. This past weekend, I cleaned out my TB (without moving the butterfly valve) and did the ECU reset, blah blah blah again. Well the idle issue did get a little better, but the sensitive 1st and 2nd gears are still there.

B.) Motor mount/gearing theory - The lower gears have a very high torque multiplication making your inputs to the throttle very sensitive in those gears. This sensitivity is magnified as the engine/transmission rock back and forth. The stiffer motor mounts will help this issue, but will not prevent it. It's something we have to live with (along with several other cars that have this issue; electronic and cable throttles alike).

LA02MAX

iTrader: (3)

Stable idle is very hard to achieve, even with extremely mild cams such as ours. It will usually vary up to 50 RPMS pretty regularly. My idle is as stable as it has ever been, but it usually settles down to 550 now (450 before I cleaned the TB) after a bit of driving. Although the accelerator pedal is completely released while in gear, the electronic throttle still keeps the plate a little open at higher RPMs, which again doesn't necessarily disprove your theory, but it doesn't help it....

P. Samson

I don't think that you'll believe me, but the hot, no load idle, after giving it a couple of seconds to "settle", should NOT fluctuate, and unless I misread your last post, you appear to have less than a stable idle. Changing the load on the engine (AC, steering etc.) might give you a momentary tach "twitch", but that's all. I've driven a couple of Gen. 5.5s and didn't notice anything but a stable idle, my friend's '99 Maxi, another friend's Taurus Duratec (which I drive regularly), my '00 Maxi, and my '05 Focus, all have dead stable idles. I still think something isn't quite right with your car.

LA02MAX

iTrader: (3)

Oh no, my idle is perfectly stable. What I was saying is that although you can't see or feel it, the idle is constantly varying up and down within a range of 100 RPMs or so. If you're monitoring the idle with something like the consult II, autoenginuity, or uprev cipher you can see this variation (although you cannot feel it). My car is perfectly fine but like I mentioned earlier my motor mounts are almost gone (wheel hop out the rear) which further accentuates this bucking motion in the lower gears (only when abruptly releasing the throttle)