Engine characteristics

[altezzaz]

When I slow down - just back off the throttle from about 3000 rpm the exhaust (and maybe the engine) backs the car "rumble" - anyone else experienced this?

[javadude]

I can't hear anything over the stereo :D - I'll turn it down and have a listen...

[Sillygit]

Have you corrected the problem yet? If not this may help.

It seems like I problem I had and it turned out to be the clutch - apparently this is a common fault with manual Altezzas.

To check, change up a gear, say 3rd to 4th at around 4500 rpm, but engage the clutch very slowly and softly and keeping you foot off the accelerator. The revs will drop to 3000 rpm and you may find that the rumbling noise does NOT appear. Then press down on the accelerator alittle to raise the revs and now you should hear the rumbling.

If this is the case I think you can be quite sure it is the clutch.

[Kavey]

When I slow down - just back off the throttle from about 3000 rpm the exhaust (and maybe the engine) backs the car "rumble" - anyone else experienced this?

Mine does the same, as does another Altezza I've driven. As I've got a freer flowing back box (missus) my car makes a nice noise as the car drops from 3000 to 2800 revs.

The 3S-GE engine is a dual VVTi jobby, so it has variable exhaust timing as well as inlet. I have a feeling that that point is a changeover point for the timing as it adjusts exhaust.

Mark at TDI is probably much more knowledgeable about these things and I'm sure will correct my random guessing

Anyway, suffice to say I think it's pretty normal :)

[greeneyes]

Mine does it also. Looking at the (translated!) Japanese enthusiast's pages, it is problem that Toyota will replace the flywheel for. I'll have to get used to it. :duh:

[Teddy]

This is why this site is great. You think your car is f***ed up only to see that it's a common problem with others. It's worse when am reversing up a hill. The shuddering noise the clutch makes, makes it feel like it's about to stall, which is not the case.

When am in 3rd and going round a bend after existing the motorway, it just wobbles. When am moving off in 1st and the steer in full or half lock, the clutch does the same thing.

I had my clutch changed 3 months ago and it's probably worse than the old one with was slipping anyway.

[jasestu]

Old thread I know, but has anyone new got any insight to add to this problem?

The rumble is very pronounced on mine (or maybe I'm just very attuned to it?), it’s not just a noise, but also a definite vibration. Very noticeable on smooth seal. It happens when lightly engine breaking down through 3000 rpm on flat road, slight inclines and declines. Have noticed it in gears 3 through 6. The rumble stops as soon as the accelerator or clutch is pressed.

It's most certainly not an exhaust thing - rattling heat shields and exhaust joints tend to be more of a buzzy sound and certainly not a vibration like this, nor is it the boom of induction of the drone of an exhaust.

Have eliminated drive shaft as the cause (has been replaced with minimal effect on the rumble), but it certainly plays a part in resonating the rumble (adjusting the central hanger bearing varies the intensity of the vibration a little). I don’t notice it if I’m chopping quickly down through the gears, but with a more ‘leisurely’ driving style it’s a real nuisance.

My dealer is happy to fix the problem - but only once we can establish what needs fixing!! No point in replacing the dual mass flywheel or the clutch if it's not the root cause of the vibration.

[allforumseen]

It still does it on Resist's Altezza, even after the dealer fitted a TRD flywheel & clutch for him.

While the revs that it occurs at are the same, 3200 down to 2800, the pitch has changed to a higher note. I drove his car & mine (standard flywheel) over the same roads one after the other, and it occurs most noticeably when the engine is on over-run down a hill and passing down through those revs.

I was hoping the TRD flywheel would solve it, having just bought one to get rid of the clutch shudder when cold.. :(

[jasestu]

I'd heard a rumour that replacing with a Lexus gearbox remedied the problem... but that does seem a tad extreme.

[jasestu]

It's most certainly not an exhaust thing - rattling heat shields and exhaust joints tend to be more of a buzzy sound and certainly not a vibration like this, nor is it the boom of induction of the drone of an exhaust.

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Think I might have to retract part of the above statement. It's not the typical induction boom sound, but this 3000 rpm rumble just may have it's roots in the intake. There's a theory (that I don't fully understand) that the intake runner is overcharged with air and on the overrun this causes the rumble that reverberates down through the drivetrain.

Tweaking the throttle butterfly (by tightening /loosening the throttle cable seems to alter the rumble, minimising it until the ECU re-adjusts to the new mixture. Need to do some more trials to be sure.

So this leads to the question - has anyone's intake modifications changed this rumble?

[jasestu]

The 3S-GE engine is a dual VVTi jobby, so it has variable exhaust timing as well as inlet. I have a feeling that that point is a changeover point for the timing as it adjusts exhaust.

Here's an update on that point. I disconnected the cam actuators for the VVT-i and the rumble still persists (and the car is also very gutless!!)

Grrr, this rumble really bugs me - I need to find the cause and get Toyota to fix it...

[altezzaz]

Here's an update on that point.  I disconnected the cam actuators for the VVT-i and the rumble still persists (and the car is also very gutless!!)

Grrr, this rumble really bugs me - I need to find the cause and get Toyota to fix it...

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eh? Toyota put it there in the first place.... I think you'll find that the mark 2 MR2 has the same problem, just not as pronounced

[jasestu]

eh? Toyota put it there in the first place.... I think you'll find that the mark 2 MR2 has the same problem, just not as pronounced

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That's true, they did put the noise there, but my dealer has no idea where it comes from and doesn't want to go replacing expensive parts only to find that it hasn't helped... Not a particularly good customer service attitude...

I'll just have to convince them that the gearbox is the problem, get a new one, and then get them to do something about what now appears to be the source - the engine. Perhaps replacement with a 2JZ would help? ;)

Interesting point about the MR2s, I'll have to look into that some more. I've got a few intake tweaks (playing with vacuum hoses, fuel mixtures etc) that I will try to see if they have an effect.

I've been trying to study what the ECU does around the time the rumble occurs, things like the deceleration fuel cut point and closed loop vs open loop fuel ratio control to see if any of these influence the rumble.