Voxy 1az-fse engine lumpy idle

Evening all, the Mrs has bought an 04 Voxy to cart her and her wheelchair around in, it has the 2.0 1az fse engine and while it's a nice drive, at slow speeds it can be a little lumpy, (fine when accelerating)

Being an import its typically automatic and this fault only happens when its warm (after the cold start cycle or old fashioned choke) but whenever you pull up to a junction its as though it wants to stall, (goes down to 500ish rpm) I've done various searches and a few recommend to clean the throttle body, I've done this....no change, some recommend cleaning the idle air control valve but being fly-by-wire it hasn't got 1, 

You can sometimes feel it getting lumpy/hesitating as your coasting along just feathering the throttle too

Sorry for the long winded explanation but thought the more info you have the easier to try and diagnose,

Hit me with your ideas......

Cheers Pete

be worth getting a code read done surely.?...guessing can be expensive.

On 7/5/2022 at 8:01 AM, RUToyota said:

be worth getting a code read done surely.?...guessing can be expensive.

Cheers for the reply, do these use a standard obd or is it definitely a jobd being an import?

If its just a standard obd I might be able to borrow a reader, that said there isn't a check light on either 🤷🏼‍♂️

I think you'll need JOBD.

Check the plugs, they should be Denso, these engines run rough on old worn plugs especial when warm

If you put the A/C on, does the engine idle up ?

On 7/9/2022 at 3:09 PM, flash22 said:

Check the plugs, they should be Denso, these engines run rough on old worn plugs especial when warm

If you put the A/C on, does the engine idle up ?

Sorry for the late reply, yes it idles up but only ever so slightly when ac is on, I suspect this wants the gas topping up too as its at its coldest when your driving but that's another matter,

As it happens we are away for the week in the voxy and I've been driving it and have noticed it has been a little lumpy all throughout the rev range when hot but is ok when under load (i suspect the Mrs wouldn't even notice 😆) so with this in mind I'll whip a plug out and see what the age looks like, might be worth replacing as a matter of course long term anyway 👍🏻

What are the coilpacks like for degrading as I've noticed it's got a new 1 fitted? (maybe even 2)

Worn plugs can kill a coil quickly, there is a vast range in part quality from the cheap Chinese tat to the decent name brands

Use Denso stuff and you can't really go wrong.

Denso Iridium plugs are excellent and long lasting.

Thanks chaps I'll do by best to update as we go 👍🏻👍🏻

Sorry to resurrect an old thread here but I've kind of narrowed down this problem....

Sooo here goes, I managed to download a whole electrical diagram for the 1az-fse, It included voltage and ohm values for each sensor so I set about checking each sensor 1 by 1 and replacing as a matter of course if they looked a bit tired (and were cheap enough) I finally came to the ocv (for the vvt I believe) this checked out OK but as a complete fluke I forgot to plug it back in afterwards. 

I road tested after each 1 and to my surprise I thought I'd cured it till I read the fault code that had now been thrown up (P1656) due to it being unplugged, car feels slightly underpowered without it plugged in but it no longer stalls or hesitates, 

Great I thought, new valve ordered and fitted, drove like a dream but today when the Mrs drove it for an hour or so and got it fully up to temp it stalled twice on her at junctions,

sorry for the long winded explanation but what could the fault be now I know the area where I'm looking?

Any common faults with oil supply to the valve/camshaft vvt?

Thanks again, Pete

Bump......?