Car jerks when I get off throttle

[inside]

Lately I've noticed with my 2zz spyder (running on uk celica ecu) that if I let off throttle in lift, whole car jerks (not just drivetrain).

With WOT run through gears everything works perfect, strong lift, no jerking. It's easiest to replicate if I coast at 7000 rpm. Then I let off throttle for only 2cm... car will jerk once. It also jerks if I quickly apply WOT at 7000 rpm, but less so.

As expected, it is more noticeable in lower gears, 2nd and 3rd. It is almost unnoticeable below the lift, e.g. at 5500 rpm.

During spirited driving, its noticeable when you have a small stretch between two corners, that you just apply throttle for a second and then back off, without shifting.

Any ideas?

I've checked TPS so far, and seems fine, reading normal values, no flat spots either. Maybe IACV (tho idle is fine)?

Will also check motor mounts... although this seems like fueling issue on deceleration...

[dan944]

Have you cleaned the MAF and reset ECU?

I'm not greatly knowledgable but would be my first port of call.

[inside]

Have you cleaned the MAF and reset ECU?

I'm not greatly knowledgable but would be my first port of call.

Thanks, but yes I've just replaced MAF a month ago with a new denso unit...

[dan944]

Have you cleaned the MAF and reset ECU?

I'm not greatly knowledgable but would be my first port of call.

Thanks, but yes I've just replaced MAF a month ago with a new denso unit...

Fair one. That's me out sorry.

[shnazzle]

Air filter?

[inside]

Air filter?

Anything specific about air filter? Its newly fitter bmc cda, cai in enclosed box. Its hooked to the side vent, then cda box, then very short stock maf tube to TB.

It is indeed a very short piping and perhaps with some ram effect. I also wondered if that could cause the surge after TB is closed (e.g. when IAC "follows throttle" and opens up, but the amounted air is fair greater... however, just a speculation). But if nothing else pops out, I'll try rerouting it just to eliminate this being the cause...

[shnazzle]

I was just thinking whether it's clean.
2zz is stupidly sensitive to intake.

But it won't be the actual intake as I assume that hasn't changed since before this issue.

[inside]

Actually I've had some extent of this issue since I've upgraded to 2zz, although with another filter. But it was routed similarly, very short and behind the battery.

The issue is not that obvious since not present with WOT runs. But once you pay attention, its easy to provoke it.

[jonbill]

What is meant to happen to cam positioning when you close the throttle like this on the 2zz? Does it drop to low lift or stay up?
What condition is the chain tensioner? No tension on the cam chain at revs can play havoc with valve timing when you lift off.

[james_ly]

If it's the engine mounts you'll notice it a lot when you change gear.

[mikek]

From what I understand 2zz is very sensitive to the position of the MAF. The MAF needs to be a certain distance from the throttle body for it to work correctly. I think @andibell had a similar issue which he solved by moving the MAF further away. Ive seen Similar issues on 2zz where air filter is behind the battery and MAF pipe gets very short.

[inside]

From what I understand 2zz is very sensitive to the position of the MAF. The MAF needs to be a certain distance from the throttle body for it to work correctly. I think @andibell had a similar issue which he solved by moving the MAF further away. Ive seen Similar issues on 2zz where air filter is behind the battery and MAF pipe gets very short.

Thanks, that definitely hints into maf/piping direction. I'll try to test this out asap.

Also, since I see you too have bmc... would you share your setup, piping? Cheers

[mikek]

Maf is 30cm of straight pipe + 90 degree bend from throttle body

[inside]

Maf is 30cm of straight pipe + 90 degree bend from throttle body

Any chance you make a picture of it? 

[mikek]

I tried but just get an image is too large message.

[dan944]

I know it's not 2zz and the maf is further away but yo get the idea. Lol.

[inside]

Thanks @dan944! This is something I'm aiming for now, I've just ordered an elbow like that...

[dan944]

Thank mike. I just had a photo from 2013 lol.

[mikek]

I have sent a photo of mine via email. Everytime I try to post a photo from my phone it says the file is too large

[dan944]

I have sent a photo of mine via email. Everytime I try to post a photo from my phone it says the file is too large

I have to use Tapatalk

[delhusband]

I have sent a photo of mine via email. Everytime I try to post a photo from my phone it says the file is too large

I have to use Tapatalk

Quick tip - if your file size is too large, try taking a screenshot of it (phone or laptop), and post the screenshot instead

[mikek]

I have sent a photo of mine via email. Everytime I try to post a photo from my phone it says the file is too large

I have to use Tapatalk

Quick tip - if your file size is too large, try taking a screenshot of it (phone or laptop), and post the screenshot instead

[mikek]

I have sent a photo of mine via email. Everytime I try to post a photo from my phone it says the file is too large

I have to use Tapatalk

Quick tip - if your file size is too large, try taking a screenshot of it (phone or laptop), and post the screenshot instead

Great tip, that wotks

[delhusband]

Mod - unrelated discussion moved here
Can I have a shot in someone's 2ZZ?

[inside]

Some update, but no solution yet.

I've tried some obd2 logging and multiple configurations of airbox with longer pipe, all with oem maf housing. However there's no detectable/clear change in relation to slight jerk when off throttle in high revs. I will be going back to SRI intake route, because the AIT are few degrees lower, and also the noise is much more attractive (except the suction noise on idle).

What I've noticed though is my LTFT trims are negative... which might be related or not, but I'll open a separate thread for that one.