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Throttle Position Sensor (TPS) intermittent harsh gear changes and idle problems


TubbyTwo

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Will re do mine then. Gone back to how it was on the way home tonight. Nice and sharp in 1st 2nd and the start of 3rd. back to lots of lag that doesn't thump in at 4k.

 

If in 4th on the auto box and i put the pedal down it really seems to lag on acceleration with not much boost, if it changes to third its much the same. Labours alot, engine sounds louder but there isn't the speed to match. If it was a manual i guess it feels like the clutch is slipping lower down the rev range.

 

 

If i kick it down it takes off like a rocket.

 

The ssqv doesn't always sound right either, sometimes its the normal high pitch noise, others its a loud whoosh noise that sounds like its from the back of the engine.

 

Any ideas?

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I'm going to be honest I haven't read the whole thread as I'm on my phone at work, but it does sound like you have something a long the lines of a sticky VSV as you say it seems to struggle/be laggy in 3rd/4th but kick down it sorts itself and goes. When it goes are you reaching 1.2 bar, as if you are that suggests the 1st turbo is fine and it may be a sticky VSV which is forced open when in kick down :) (please tell me to shut it though if it's bin mentioned above lol)

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What revs are you at when it struggles? I bet it's below 4000rpm, and kicking down puts it above 4000rpm :)

 

Also, the top 4mm blue hoses in your picture aren't vac hoses, they are the windscreen squirters :D

 

And if your idle has gone from 900rpm to 1100rpm, that's about right for one hose not being connected after the throttle body. The engine gets extra air and the idle goes up. Check the power steering valve hose at the front outer side of the plenum.

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Hi Ian, by ICV do you mean the Intake Air Control Valve (IACV) ?

 

Yes :)

 

If you boot it below 4000rpm, it may vent boost back through the IACV reed valve into turbo #2, which isn't spinning and will just let it go back out to atmo. Not enough for a full on boost leak, but enough to dent boost production down to your 0.5bar. When you're above 4000rpm (via kickdown) both turbos are getting exhaust gas and producing boost so the reed valve is irrelevant. I would assume that you don't feel the effect so much in 1st/2nd gear as there is still enough power at lower boost to feel quick. Unless you've seen it on the boost gauge in which case :shrug: for now.

 

It may be the IACV actuator/flap isn't shutting fully which would give the same behaviour. both are a component that can be intermittent, and rather hard to spot. And neither problem is solved by swapping hoses, so it kinda fits where you're at. It's all part of the same unit, so swapping it with a known good one would be an easy test. It's even on top of the engine, you lucky fella :D

Edited by Ian C (see edit history)
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I'm going to be honest I haven't read the whole thread as I'm on my phone at work, but it does sound like you have something a long the lines of a sticky VSV as you say it seems to struggle/be laggy in 3rd/4th but kick down it sorts itself and goes. When it goes are you reaching 1.2 bar, as if you are that suggests the 1st turbo is fine and it may be a sticky VSV which is forced open when in kick down :) (please tell me to shut it though if it's bin mentioned above lol)

 

I am wondering if it worth getting some VSV's to swap and test. Yes it will hit 1.2 bar AFTER 4k rpm once kicked down. :)

 

What revs are you at when it struggles? I bet it's below 4000rpm, and kicking down puts it above 4000rpm :)

 

Also, the top 4mm blue hoses in your picture aren't vac hoses, they are the windscreen squirters :D

 

And if your idle has gone from 900rpm to 1100rpm, that's about right for one hose not being connected after the throttle body. The engine gets extra air and the idle goes up. Check the power steering valve hose at the front outer side of the plenum.

 

Yes Ian, it struggles below 4000 rpm most noticeable in 3rd/4th. I did do a quick spot check of all the hoses on the intake plenum side, all APPEAR to be ok although they are all hard so possible split perhaps. These are next on the list to replace with silicone vac hose. from looking at the vac diagram from your post the only hoses I havent managed to replace are the ones to the pressure tank.

 

image

 

Yes :)

 

If you boot it below 4000rpm, it may vent boost back through the IACV reed valve into turbo #2, which isn't spinning and will just let it go back out to atmo. Not enough for a full on boost leak, but enough to dent boost production down to your 0.5bar. When you're above 4000rpm (via kickdown) both turbos are getting exhaust gas and producing boost so the reed valve is irrelevant. I would assume that you don't feel the effect so much in 1st/2nd gear as there is still enough power at lower boost to feel quick. Unless you've seen it on the boost gauge in which case :shrug: for now.

 

It may be the IACV actuator/flap isn't shutting fully which would give the same behaviour. both are a component that can be intermittent, and rather hard to spot. And neither problem is solved by swapping hoses, so it kinda fits where you're at. It's all part of the same unit, so swapping it with a known good one would be an easy test. It's even on top of the engine, you lucky fella :D

 

Right ok chap thanks, will try and source an IACV actuator then for a test. I will get the camera mount in the car tonight and film the speedo/revs/boost controller, will also make it a bit clearer how it drives.

 

Thanks for the help so far guys, really appreciated. :)

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Right, checked bov that's all good, completely blanked off the vsv above alternator as in the pics above from Samurai20v.

 

Idle is back to 900rpm once warm and stays constant.

 

Factory reset the HKS EBC to see if that made a difference. No change.

 

Only hoses that couldn't be replaced are the 4 in this picture:

image

 

And the ones to pressure tank:

uploadfromtaptalk1351023646703.jpg

 

Rod to the IACV above turbo #2 moves but isn't loose feels ok.

 

So guess swapping valves is the next step unless people think its worth replacing hoses in pictures in this post.

 

Also have a video clip of how the car drives so will upload that shortly.

 

Getting annoying now.

Edited by TubbyTwo (see edit history)
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sorry i havent read through the thread completely, but if you are in doubts about the ebc, pump its all back to stock as i know that the avcr ebc can cause low boost from first turbo if not switched on, its always a good start to do everything set to stock so you can eleminate more things easily.

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Will try this at the weekend, cant think it will make any difference though mate, the boost controller works fine.

 

if your not making boost you want from the first turbo then i would say its not.

just re read thread so you have put back to stock and its the same

 

nice and simple test for you here put the car into TTC drive to preasurise the system then park up turn car off wait about 2 minutes and pull off one of the vac hose off the iacv vsv and if it releases preasure you dont have a leak anywhere :)

 

but if there is no preasure realease the there is a split pipe somewhere

Edited by mellonman (see edit history)
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