Jolting when letting off the gas

[SoniCraze]

This might be pointless but im sure you all know what im talkin about.

Its really bad when your in 1st but it really happens in all gears. When you just let off the gas, or even if you are really slow, the car will jerk. 1st is by far the worst, it could be in one of those choclate mild comershals(shake stuff up)

Basially wtf causes this? fuel mangement?

This isnt a HELP ME thread, but more a open discussion..kinda like the lets kill the turkey one we had awhile back.

 

[low_psi]

its your motor mounts. one moment the engine is torqued back and the next its thrown forward. its normal for ANY car with soft mounts, but most notable on fwd cars because of the transverse drivetrain setup.

 

[SoniCraze]

really?

I do feel it in other fwd cars, a little in the srt-4 i driove, but NOTHING like in a msp. Its just nasty, im "most" other cars ive driven you can drive around in first, then let off the gas and it will hit but not jolt, in my speed.....whoa...its like im lerning to drive all over again.

 

[low_psi]

that's just the nature of the beast.

 

[oldzoomer]

Interesting. I had been assuming it was an engine issue and not a mount issue. My old Protege didn't buck between gears like this one does. I wonder if Mazda softened the engine mounts.
Anyway, lots of threads on replacement mounts. I may consider them at some point.

 

[jflo]

when u let off the gas is it a sudden motion or gradual step off ? and how long has the car been running when you do this ? when this happens to me, it's usually when the car has been running for quite some time, or i'm letting the gas off really quickly causing the flow of air to slow dramatically through the throttle plate causing the engine to bog a lil' bit. or it could even be when your stock pipes are expanding from the heatsoak

 

[Mach 3.5 Turbo]

I always assumed that it was caused by the transition from the engine driving the car to the car driving the engine. You suddenly change the direction that all the torque is acting on all the gears, driveshafts, wheels, tires, differential, clutch, etc. I figured it's the lash of all these parts getting tight the other direction, "slop" if you will. Also the damper on the clutch has to travel through a certain rotation to unload the springs, then wind up on the coast side. I'll ask the guys at work today what this is, I'm an engineer at a clutch factory. I'll keep you posted

 

[Mike R]

I always assumed that it was caused by the transition from the engine driving the car to the car driving the engine. You suddenly change the direction that all the torque is acting on all the gears, driveshafts, wheels, tires, differential, clutch, etc. I figured it's the lash of all these parts getting tight the other direction, "slop" if you will. Also the damper on the clutch has to travel through a certain rotation to unload the springs, then wind up on the coast side. I'll ask the guys at work today what this is, I'm an engineer at a clutch factory. I'll keep you posted

You are correct, but with the mazdas the motor mounts are quite puny compared to say....a honda civic (has 5 mounts vs 4, and the mounts are 3 times the size as the protege). It is the nature of the beast that there will be some movement, but most FWD cars do not have it as severe. Even my ancient 200K Tercel wasn't as bad as the brand new protege. I bought the AWR mounts and the lash is bearable now, at the cost of some added NVH.

 

[ONRAILS]

I get a major jolt when I am say, in 4th gear, hit the clutch, put it in 5th and hit the gas (right there), it bucks like a bronco. I don't believe that has to do with the motor mount, it's more a hesitation or something. I am sure it is more pronouced cause of the mounts though. It seems like for a sec there, it has no air, or fuel... something.

As far as the jolting in lower gears going slow... guess you just have to get used to feathering the throttle. I had that issue at first, but not anymore.

 

[Maniac0301]

Stickney: your issue may be with the VICS depending on temperature and rpm range

Our first gear is pretty low and I don't think the fly wheel is very heavy this causes the transition from on or off the gas to be worse than other fwd cars. Just be smoother on the gas in first gear or tool around parking lots in 2nd gear. 2nd gear works just fine at 10mph or so. My Neon had solid motor mounts and it would still buck badly if I were in first gear and let off the gas suddenly.

 

[ONRAILS]

Maniac... educate the dummy here. What is VICS?

 

[Maniac0301]

The way I understand the VICS to work is that it is a valve that changes the shape/dimensions of the tracts in the intake manifold. The VICS opens the intake tract up at around 4000rpms depending on temperature and whatnot. Some users have disable the VICS to be open all the time and that seems to remove some of the jerkiness you get if you shift just past 4500rpms or so.

 

[girth]

People are soon going to get sick of me making this post because I've made it quite often lately, but here goes.....

I have this same "jolt" in the drivetrain when I let off the gas. It is even MORE pronounced when I "feather" the gas or lightly let off because that's when you're least expecting a big "jolt." It seems to do it in spurts -- 1 short drive it will do it all the time and the next short drive it will never do it. Both my MSP and my 2000 Protege ES didn't do this until there was some miles on the car (over 7500). My MSP does it the worst in 4th gear when I LIGHTLY let off the throttle - there's just a huge JUMP in the drivetrain. My 2000 ES would do this in 4th and 5th EVEN WITH THE CRUISE ON -- i.e. when the cruise control would tell the car to "coast" for a split second to reduce the speed the whole drivetrain would jump when the coasting started and then jump again when the cruise applied the gas. It is really quite rediculous! If there's any passenger in the car when this happens they WILL be like "WTF - don't you know how to drive?" There is no way to alter your style of driving to prevent it from happening either -- it litterally does it randomly. I've come to the conclusion that Mazda's Protege drivetrain is just an unrefined POS. There's no other explaination. Of course I can't take this or my previous Protege to the dealer to look into it because it inevitably won't happen when they drive it - and even if it did they'd just classify it as "a characteristic of the car" since it doesn't seem to cause any mechanical or safety harm.

 

[SuperSpud]

its your motor mounts. one moment the engine is torqued back and the next its thrown forward. its normal for ANY car with soft mounts, but most notable on fwd cars because of the transverse drivetrain setup.

no marc, its not the mounts...


there have been several threads about this.. I believe teh conclusion was poor fuel map or something.. either too much air or gas is being let into it, and when you let off the gas, it doesnt know what to do.. something like that... mine does it REALLY bad in second.. thats the only gear I really have it in....

 

[Newf]

ok, the jolt in 1st is common on a lot of cars. Matter of fact every 4 cyl 5 speed I've driven has done this. This is what happens when you have a peppy car, that's a stick, and your not driving it right. Nothing wrong here....relax.

The Jolt while moving in other gears I felt before I had the flash, now I don't at all unless the car is REALLY cold in which case again, any car I've had that's really cold has done the same. Honestly, it rarely happens and when it does I know it's because I never let it warm up enough.

Girth.....not sure about you, that's a little too much of a jolt from your explanation above.

 

[Autox MSP]

it happens at 4k rpms, its a big hole in the fuel map.

 

[girth]

Girth.....not sure about you, that's a little too much of a jolt from your explanation above.

I agree - I'm 99.99% sure my situation is NOT fuel related. I agree with the 1st gear thing you mentioned -- I mean that's how such a low gear is going to work.

But yeah, my situation is in the higher gears - 4th and 5th. I know it is not fuel related because the ENGINE is fine (only the drivetrain/tranny jumps), it happened in my 2000 ES too, and it's not normal for it to happen with the cruise control on. Mazda Protege's are the only cars that have ever had this type of drivetrain "lash" for me.

I honestly believe that more and more people will experience exactly what I described in my other post within the next year of owning their MSPs. And when it happens you will KNOW it - it's not something you have to pay attention for. It will happen first to the people that are in a lot of slow-moving traffic ---- I have never experienced it at speeds higher than 45MPH. It's the worst from 25MPH to 40MPH in 4th or 5th. I hope that as it happens to more people they post about it ... that's the only way Mazda will ever know it's an issue.

 

[02.5 P5]

IT IS NOT THE MOTOR MOUNTS!!! i have the AWR's, it is a PCM issue. when you let off of the gas, the mixture is acutally hitting right where it needs to be, so you are acutally making more power because the car gets the right amount of air and fuel and timing for a split second. you can make it do it in every gear, but it will be more pronounced in some than others based on your driving style. try driving on the freeway, in 5th, give it some gas and let off. most likely it will surge forward. this car needs some real engine management, that will solve the problem, along with a good FMIC, of course.

 

[tddelsol]

every car ive had has done this (all fwd) it is part of having a standard as far as i know. leave the clutch slightly engaged if its that bicg of a concern or better yet why are you driving around in first

 

[rocketspeed]

What are you doing lugging around in 4th and 5th at 25-40? I don't think MSP's are very happy cars in the low part of the RPM band. Sounds like the engine is straining to pull that high gear at low speed and twisting itself into knots in the engine bay.

I experience a lot of lash through the drivetrain/bucking, but it pretty much can happen in any gear and it usually happens around 4k when you're into the boost and let up on the throttle quickly. The car bucks. I just figured it was a quirk, I've also attributed it to engine management. Something I can live with.

I agree - I'm 99.99% sure my situation is NOT fuel related. I agree with the 1st gear thing you mentioned -- I mean that's how such a low gear is going to work.

But yeah, my situation is in the higher gears - 4th and 5th. I know it is not fuel related because the ENGINE is fine (only the drivetrain/tranny jumps), it happened in my 2000 ES too, and it's not normal for it to happen with the cruise control on. Mazda Protege's are the only cars that have ever had this type of drivetrain "lash" for me.

I honestly believe that more and more people will experience exactly what I described in my other post within the next year of owning their MSPs. And when it happens you will KNOW it - it's not something you have to pay attention for. It will happen first to the people that are in a lot of slow-moving traffic ---- I have never experienced it at speeds higher than 45MPH. It's the worst from 25MPH to 40MPH in 4th or 5th. I hope that as it happens to more people they post about it ... that's the only way Mazda will ever know it's an issue.