Jimny VVT less power at low revs than non-VVT?

As said, the Suzuki VVT is just a hydraulic phaser unit on the inlet cam pulley. At idle the inlet cam rotates backwards relative to the sprocket to full retarded timing, on load it advances the cam timing. Control is achieved by measuring the inlet cam timing with the cam sensor above the bell housing and vibrating the VVT solenoid control valve backwards & forwards

If the VVT control valve is stuck or the little built in oil filter bunged up it may be on full retard all the time, but I'd expect P0011/P0012 to be set if the desired cam timing relative to the crank couldn't be achieved.


If it is down on power I'd look for restrictions in the exhaust (like a partly blocked catalyst) and inlet (like a blocked or soggy air filter)

Thanks for this. I did replace the catalytic convertor last year. Also, changed the air filter just last week, and did a compression test which seemed ok (all between 140 and 150)

Mine goes so much better than a std gen3 (and gen4 ) mine is 235, 17% gearing, VVT and m16 and even pulling a trailer it is faster up hills than a std jimny

You say you changed the cat, but there is two of them. (sorry for nagging on and on about them).
could it be you changed the broken number one and the powder from it has clogged the next like mine?
I went from doing my test hill in third gear just barely making 80kmh, to doing 120kmh in fifth after replacing the two broken cats with one generic cat for 2.0 motors.

Thanks, Yakuza. I have been thinking about this. I did change the front cat and after that the car went from almost undrivable to what I thought was normal, but maybe the rear cat has problems like you say.

I will get the car booked into an exhaust place to check this.

I was just looking at the O2 sensor voltages at idle.

Does this sensor 2 voltage look wrong? What does it tell me?

​​​​​​thanks
Lee 

Sensor 1 pre-CAT should look like that, the post-CAT sensor should be smooth. Basically it is measuring how much oxygen there is.

The pre-CAT sensor is used to fine tune the fuelling, the post CAT sensor is there to tell if the CAT is working. If the two are both the same or very similar then the CAT has failed.

However, sometimes at tick over there isn’t enough gas going through, check the two traces at a steady rpm, preferably whilst driving at a steady speed.

Robin

Ignore everything I just wrote, I only saw the red trace which looks normal for sensor 1. Sensor 2 looks like it has gone full scale and looks like a sensor or connection fault.

Try a little throttle or blipping the throttle, does it ever change? If not it’s a connection or sensor fault. I would also expect you will get an OBD fault code for this.

Robin

Thanks, Robin

There is no fault on the OBD... I'll try a little throttle tomorrow morning. If it doesn't change then I could try replacing the second O2 sensor after the cat?

Would a failed O2 sensor after the cat cause any performance issues? Or only the sensor before the cat?

tomlil01 wrote:

Thanks, Robin

There is no fault on the OBD... I'll try a little throttle tomorrow morning. If it doesn't change then I could try replacing the second O2 sensor after the cat?

Would a failed O2 sensor after the cat cause any performance issues? Or only the sensor before the cat?
 

Usually no. It just puts the EML on with an emissions fault because it can't monitor the cataylst.

I could be wrong and it goes into limp mode, but certainly other makes that I am familiar with don't.

It should be around 0.9V indicating no oxygen, so it is out of range.
 

I think the 1.2v was a red herring. After warming up the car with a drive it was about 0.8 on sensor 2 at idle, and crept up slowly to 0.95 after 5 or 10 minutes of idling.

Driving with the engine under load it was about 0.85/0.9, and dropped down to near zero when taking my foot off the throttle.

Is this a sign that the cat is gone? I have replaced the back (1 year ago), but not the front.

Is the front easy to change so you know?
Thanks
Lee

The steady 0.9V means the cat is working.

Whether the cat works or not doesn't affect how the engine runs. What we've been telling you is that a partially blocked catalyst will restrict the engine power because the exhaust can't get out fast enough and back pressure builds up.

What tends to happen is the front catalyst blocks and starts to break up and crumble, then the dust & fragments lodge in the rear catalyst blocking it.

Other members have simply had the broom stale to the front catalyst and rodded it out to an empty pipe, then run with just the rear catalyst and it still passes emissions at MOT.

I think the front catalyst is part of the manifold, easy enough to change, but spectacularly expensive!

0.9v means it's working? My understanding was that it was that it should about 0.45v on the 2nd cat.