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

[Ian C]

I'm on nightshifts at the mo mate, I'll have to try and remember to check

[TubbyTwo]

Thanks mate appreciate it

[listy]

Cheers, last night didnt end well when I bashed my elbow, spun round and elbowed the bonnet stay which promptly brought the bonnet down on my back. Which the wife found hillarious.

 

Sorry mate but

[TubbyTwo]

she laughed as well

[TubbyTwo]

Right put the boost controller back in and have put the car in TTC mode. just got back from a run and aside from sounding rather loud it runs fine. Boost is spot on and after a bit of tweaking got it to hold 1.2 bar.

 

So from that assume the seqential system is ok. after tomorrow's drive to work i will pull a hose off and test for pressure.

 

So guess from that its got to be a vsv?

[mellonman]

or a split vac hose, did you manage to change the one's right at the back of No 2 turbo pig to get too?

 

did it spool better in TTC which might indicate what i said about the iacv slightly open or sticking check the stopper screw cant hurt, with TTC everything is opened fully so you would be loosing boost back into second turbo as it would be spinning also

[TubbyTwo]

I have not yet managed to change the 2 boost hoses at the back of the engine bay yet, got to move my alarm siren out the way first so thats this weekens job, along with the hoses to the pressure tank. Car spools fine, making full boost and both turbos hit hard. Not enjoying the drone or lack of low down grunt tho, but its only tempory.

 

Turbos are both making over 1 bar by 3800 rpm ish and pull hard to 1.2 bar.

 

anyone know the sizes of the vac lines to the pressure tank? assume they are 4mm?

[mellonman]

check the screw mate, pull the vac pipes off release the preasure , under screw and check if the iacv arm moves with the screw,

 

realisicly though your boost controller should be able to put what ever boost you want through the first turbo as it works as the waste gate.

this link explains it very well and will help you no end, its such a same as i had all them bits the other week when you was first going to come and get the stock air box off me,

 

http://www.google.co.uk/imgres?imgurl=http://www.max-boost.co.uk/max-boost/images/supra/sequential/IACV_movement.jpg&imgrefurl=http://www.max-boost.co.uk/max-boost/supra/turbo.htm&usg=__POS3K2dopWF8CVcv5lywP7PJ8VE=&h=214&w=293&sz=13&hl=en&start=24&zoom=1&tbnid=nj394wTAp5XBiM:&tbnh=84&tbnw=115&ei=0haRUOvHDoy1hAfb5ICgBA&prev=/search%3Fq%3Dsupra%2Biacv%26start%3D20%26hl%3Den%26safe%3Dactive%26sa%3DN%26gbv%3D2%26tbm%3Disch&itbs=1

[TubbyTwo]

Ok buddy cheers. will repalce the last few hoses then take the IACV off and check it. Will also test the VSV voltage as well.

[mellonman]

i wouldnt actually take the iacv off just undo the screw to make sure its not holding the veav open slightly, it has alot of tension behind it so its doubt full to get stuck

[TubbyTwo]

Will do

[TubbyTwo]

Righto.

 

car is back to sequential mode, had enough of TTC. After driving and pulling a hose of the IVAC VSV there is a loud hiss, so the vac system checks out and doesnt leak, no split hoses there.

 

Back to the IVAC, multimeter packed up so need to source another to test the voltage of the vsv.

[mellonman]

did you check that screw ?

at least you know the vac pipes are good thats a good start

 

you can get a meter for as little a £5 now days

[TubbyTwo]

Had a quick look, where is the screw? Where the actuator arm joins the pipework?

[mellonman]

yes pritty much i will try and dig out a pic from somwhere

 

you should be able to do this in place with a set of pliers,just make sure that the screw is not stopping the arm coming down all the way,undo the screw until you can see a small gap under it then tighten back up to the arm so its just touching then go test you car.

Edited November 8, 2012 by mellonman (see edit history)

[TubbyTwo]

Ah ok, that clears it up, thanks mate

[TubbyTwo]

Finally got hold of a multimeter tonight. Tested vsv as per manual which states resistance should be between 38.5 to 44.5 ohms.

 

Mine came back at 50.4 so well outside the norm.

[TubbyTwo]

can anyone tell me the sizes of the pipes circled in the pictures below? want to replace the 2 ribbed hoses on the turbo pipes and also the pipe that joins onto the IACV.

 

need to know the IDs of these pipes so I can order some reinforced silicone ones.

 

[TubbyTwo]

Swapped the VSV out for a working one, and its hasnt solved the problem. Now the 2nd turbo doesnt kick in fully until about 5k rpm FFS.

 

Will try a new IACV from IanC, failing that I will either take the car to a specialist or break it starting to lose the love now.

[TubbyTwo]

Off to meet up with IanC tomorrow for good look, hopefully we can narrow it down!

[mellonman]

no boost until after 5k mean that the vsv that you have tried is no good or the vac pipe to it mate, have you checked the screw yet or what, you might need to change the hole iacv by the looks of it

[Ian C]

Righto, had a blast in the car today and found these tasty facts out:

If you put it in L or 2 (autobox), the sequential system works correctly every time.

If you put it in D and give it enough throttle to get on boost in 2nd but avoid kicking down, it's kinda flat on the first turbo

If you put it in D and give it some in 3rd, it's very flat on the first turbo and the revs stick at around 3000rpm while the road speed catches up.

 

Here's some piccies, youtube vid to follow...

 

Note here, cruising in 2nd gear, the speed discrepancy for the same revs (speedo is in KMH):

 

We booted it from there, and here is the difference between manual 2nd and Drive 2nd by the time the 2nd turbo starts to come in:

The "drive" one was actually already on some boost so it even had a bit of a head start, however in manual mode it's gotten a few mph and nearly 500rpm ahead...

 

I think this is nothing to do with the sequential system, as in manu L and 2 it works fine every time. I think it's the autobox. It's either slipping when in D/3rd and using the engine power to heat the transmission fluid instead of drive the wheels, or the electronics are confused and it's retarding the timing thinking it's changing gear.

 

I've not got much experience with the auto or autos in general, so other people need to contribute here - the fluid was over the "full" marker on the dipstick but otherwise still red and clean, and wasn't burnt. Can the stall converter or something else in an auto go wrong to the point where it saps performance in Drive but not in the manual modes?

 

The YouTube vid I'm sorting out will show you the different behaviours and the bizarre slip at 3000rpm in Drive.

 

-Ian

[Ian C]

Youtube vid here:

 

http://youtu.be/V82vZkl3yb0

 

The last bit is a synchronised start of 2nd gear, Autobox on the left, manual mode on the right. The audio is autobox first, manual second. Note the difference in performance. it's like putting it in drive sucks up a load of power

[TubbyTwo]

Massive thanks for having a look today, good to meet you and Alex!

 

Had a blast on the way home and through the gears manually shifting its fine.

 

Hopefully some autobox tech heads will very able to shed some light. ran out of daylight by the time I got home so will drain and refill the autobox with new fluid this weekend. And see if that makes a difference.

[Alex]

Good to meet you too mate Hope you get her fixed...or at least diagnose it fully soon.

 

The video is odd. Speed allegedly going up but revs not in manual, I would GPS the speed in Auto/D mode to see if the speedo is right or not.

 

I assume that the auto box "locks up" in manual mode...from my inexperienced viewpoint it seems like in D it never locks the converter.

 

It could be down the the oil...what is in there?

 

Wonder if the chap on here that does the hybrid boxes would know...or someone like Leon Green who's had to deal with a billion and one autobox issues.