VVTi TPS and IACV VSV

[spartan]

To avoid confusion, by TPS I mean Throttle Position Sensor and IACV refers to the Intake/Inlet Air Control Valve.

 

I know that there have been a few reported cases of problems with the TPS on the VVTi but, touch wood, I have never experienced any of these problems (mine's a tiptronic, in case that makes a difference).

 

However, throttle response does appear to be a bit 'vague' at times. A couple of things I've noticed that I would appreciate comments/feedback on:

 

• with everything switched on, bonnet/hood open but engine not running, the TPS is very noisy/whiney and I don't just mean when opening/closing the throttle via the cable; it does this even at rest. I assume there's some kind of stepper motor involved but I'm pretty sure it shouldn't be making this kind of noise.
  
• I have a Greddy Informeter fitted and one of the things that it can display is % throttle opening. This shows some rather bizarre readings! If the throttle is closed it shows about 20%; if opened slowly and progressively, the % rises steadily up to 100% (105% sometimes?!); if opened very quickly, the % jumps up to say 60% and then doesn't move even if making slight adjustments to the throttle opening. I'm guessing these readings are because the VVTi TPS is measuring rate of change of throttle opening, rather than actual throttle opening (the ATP does this?). Even so I don't understand these readings at all.
  
• Whilst conducting these tests, I noticed a loudish clicking from the back of the engine. I narrowed this down to the IACV VSV and, if I disconnect it, the clicking stops. Now, I've checked the IACV VSV using a multimeter and it appears to be fault free. However, what I've discovered is, if you open the throttle fairly quickly, the IACV is opened at about 1/4 throttle and closed at about 1/2 throttle (remember all these tests were conducted whilst the vehicle was stationary, engine off); if the throttle is opened slowly the IACV remains closed. More accurately, the VSV is actauted (the clicking) - I never actually saw the IACV move which I guess means there is nothing in my pressure tank (is that right?)
  

 

Thanks for any enlightenment!

Edited March 8, 2010 by spartan
Disambiguation of IACV/VSV (see edit history)

[chrispot]

To avoid confusion, by TPS I mean Throttle Position Sensor and IACV refers the Intake/Inlet Air Control Valve.

 

I know that there have been a few reported cases of problems with the TPS on the VVTi but, touch wood, I have never experienced any of these problems (mine's a tiptronic, in case that makes a difference).

 

However, throttle response does appear to be a bit 'vague' at times. A couple of things I've noticed that I would appreciate comments/feedback on:

 

• with everything switched on, bonnet/hood open but engine not running, the TPS is very noisy/whiney and I don't just mean when opening/closing the throttle via the cable; it does this even at rest. I assume there's some kind of stepper motor involved but I'm pretty sure it shouldn't be making this kind of noise.
  
• I have a Greddy Informeter fitted and one of the things that it can display is % throttle opening. This shows some rather bizarre readings! If the throttle is closed it shows about 20%; if opened slowly and progressively, the % rises steadily up to 100% (105% sometimes?!); if opened very quickly, the % jumps up to say 60% and then doesn't move even if making slight adjustments to the throttle opening. I'm guessing these readings are because the VVTi TPS is measuring rate of change of throttle opening, rather than actual throttle opening (the ATP does this?). Even so I don't understand these readings at all.
  
• Whilst conducting these tests, I noticed a loudish clicking from the back of the engine. I narrowed this down to the IACV VSV and, if I disconnect it, the clicking stops. Now, I've checked the IACV VSV using a multimeter and it appears to be fault free. However, what I've discovered is, if you open the throttle fairly quickly, the IACV is opened at about 1/4 throttle and closed at about 1/2 throttle (remember all these tests were conducted whilst the vehicle was stationary, engine off); if the throttle is opened slowly the IACV remains closed. More accurately, the VSV is actauted (the clicking) - I never actually saw the IACV move which I guess means there is nothing in my pressure tank (is that right?)
  

 

Thanks for any enlightenment!

 

i have a vvti and it make a noise from the throttle body with engine off and ignition on, i have also got sbc i colour which i connected to the tps sensor, but on checking wiring diagram there are two tps, one is attached to the throttle cable and the other via stepper motor drive, has your infometer been conected to the stepper one?. also i have connected a led display to all the vsv on the engine, and mine inlet air controll does the same, if the throttle is put down slowly it doesnt operate, but does if thottled quickly, as for the vague throttle responce mine has never been like that apart form when the traction control steps in then its like driving a transit diesel, hope this helps, regards chris.

[Pudsey]

I have never personally ever heard any noises from my engine at all, ignition on engine off or engine on idling.

 

Sometimes its so quiet stood outside by it, that you can't even tell its actually running at all.

 

Can't say I have ever sat with the car turned off pushing the throttle though, surely this doesn't do anything any good (unless your fault finding of course).

 

So no noises fom me.

[spartan]

i have a vvti and it make a noise from the throttle body with engine off and ignition on, i have also got sbc i colour which i connected to the tps sensor, but on checking wiring diagram there are two tps, one is attached to the throttle cable and the other via stepper motor drive, has your infometer been conected to the stepper one?. also i have connected a led display to all the vsv on the engine, and mine inlet air controll does the same, if the throttle is put down slowly it doesnt operate, but does if thottled quickly, as for the vague throttle responce mine has never been like that apart form when the traction control steps in then its like driving a transit diesel, hope this helps, regards chris.

 

Thanks for that Chris. The Informeter uses the OBDII port so is not directly connected to the TPS; it gets all its info. from the ECU.

 

I wonder why the IACV behaves like this? I would have thought that opening the IACV would allow some of the boost created by the first turbo to run backwards through the second turbo, i.e. boost would build more slowly if you prod the throttle rather than if progressively opening the throttle. Maybe it's an attempt to keep the power delivery smooth?

 

It would appear that my car is operating normally (I think the power delivery vagueness is just me still coming to terms with the 4-speed auto.) but I still don't understand those TPS readings ...

[chrispot]

Thanks for that Chris. The Informeter uses the OBDII port so is not directly connected to the TPS; it gets all its info. from the ECU.

 

I wonder why the IACV behaves like this? I would have thought that opening the IACV would allow some of the boost created by the first turbo to run backwards through the second turbo, i.e. boost would build more slowly if you prod the throttle rather than if progressively opening the throttle. Maybe it's an attempt to keep the power delivery smooth?

 

It would appear that my car is operating normally (I think the power delivery vagueness is just me still coming to terms with the 4-speed auto.) but I still don't understand those TPS readings ...

 

i have not checked the iacv pipework but it could be like the wastegate controller in as much that it has two pipes going to it and when the vsv operates it bleeds air through pipe whilst the other has pressure going through it, does this make any sense to you, in other words the iacv operates when the vsv is not releasing air, i have not checked on my car how it plumbed up, regarding your infometer whould it not be possible to email the manufacturer and explain your problems to them as they might shed some light on it, the mushy feeling you say might be because your are not used to autos, did you have a 6 speed before if so then i would say that is the problem as now you only have 4 gears so first in a auto is more like second gear in a manual etc. hope this helps regard chris.

[spartan]

i have not checked the iacv pipework but it could be like the wastegate controller in as much that it has two pipes going to it and when the vsv operates it bleeds air through pipe whilst the other has pressure going through it, does this make any sense to you, in other words the iacv operates when the vsv is not releasing air, i have not checked on my car how it plumbed up,

 

I think I know what you mean. I have read that, despite the VSV activating, the IACV won't actually be fully open until the pressure fed via the VSV reaches 0.5 bar; it's probably unlikely that this boost could be easily achieved at 1/4 throttle from rest (the behaviour of the IACV is linked to pressure, throttle and vehicle speed). I'm guessing that the only reason the VSV behaves like this is for 'safety' reasons (protection against boost spikes, backfires up the inlet tract, etc.). Awaiting superior technical knowledge ...

 

 

regarding your infometer whould it not be possible to email the manufacturer and explain your problems to them as they might shed some light on it,

 

I doubt it - no real support outside Japan and it's been superseded by a later model ...

 

the mushy feeling you say might be because your are not used to autos, did you have a 6 speed before if so then i would say that is the problem as now you only have 4 gears so first in a auto is more like second gear in a manual etc. hope this helps regard chris.

 

I think you are right! I did drive a UK 6-speed before. I'm really impressed with the auto. gearbox but I still miss the manual sometimes. I guess the Tiptronic is a happy medium but I wish it had a few more gears in there!

[chrispot]

I think I know what you mean. I have read that, despite the VSV activating, the IACV won't actually be fully open until the pressure fed via the VSV reaches 0.5 bar; it's probably unlikely that this boost could be easily achieved at 1/4 throttle from rest (the behaviour of the IACV is linked to pressure, throttle and vehicle speed). I'm guessing that the only reason the VSV behaves like this is for 'safety' reasons (protection against boost spikes, backfires up the inlet tract, etc.). Awaiting superior technical knowledge ...

 

 

 

 

I doubt it - no real support outside Japan and it's been superseded by a later model ...

 

 

 

I think you are right! I did drive a UK 6-speed before. I'm really impressed with the auto. gearbox but I still miss the manual sometimes. I guess the Tiptronic is a happy medium but I wish it had a few more gears in there!

 

if i find any info on the IACV I will pm you the info, as for driving a auto, I prefer it as its great in traffic and general driving and on the other times when the missus is not in the car it can still blow away 95% of cars on the road, to put it another way I only give it some! 5% of the time, when i wish i had a manual. regards chris