Tps - Is There More Than One ?

Just had a nice chat with a guy who has sorted similar 'slight throttle position' problems like mine, but on BMWs and Mitsis with FBW throttles...hes no Supe guru but hes sugesting that Supes may well have a second TPS on the throttle mech itself (he described it as a carbon runner) which may have a 'bad spot' explaining the random intermittant fault at idle speed only...anyone know if VVTIs have something similar ? I wouldnt know what to look for.

Yes

APP - Actual Pedal Position (Sensor) - the one with the cable on it....

TPS - Throttle Position Sensor

Both are on the VVTi throttle body either side of the butterfly. The APP takes the feed from the pedal (obviously) and tells the ECU how far to open the throttle...which is x-reffed by the TPS...I think.

Can you explain more about this idea he had?

specifically he has fixed 'many' Mitsis / BMWs by replacing a TPS located on the accelerator pedal assy, (hes learnt that its this one that is more likely a culprit than the one at the actual throttle body) I stress that hes not had to deal with this problem on a Supe, but he seemed to suggest that a pedal mounted sensor (linear, prone to wear / dirt) was more likely to play up than a stepper motor sensor that just takes current....by now youl have realised that Im not technical, but if there aint a sensor down there (like some BMWs) sorry for the red herring

No that's good info thanks...I've wondered about it...but at £100+ I can't afford to just throw money around on something that "might" help.

Ok I'll calibrate my TPS...though I don't expect miricles...I'll also set about pulling off the APP and see if properly cleaning this gains me anything, as certainly my last mega clean of the throttle body itself.

If I manage to collar a local guy (V) and nick his APP to test this could help too (as his works perfectly (git!)

Ewen, I pulled apart my APP...and it was clean inside

The only thing that was dirty was the springs...but I gave it a healthy dose of cleaner anyway.

So far no change to report - more testing needed.

I'm getting closer and closer to the point where I just say "f**k it" and buy a replacement Throttle body or a known working secondhand one.

I do not know if its the TPS, APP, Throttle butterfly or the Temperature sensor...and diagnosing electical problems in not something I can do.

I will try going to Toyota for an ODBII check...unless you've done that already?

To actually relace the TPS and the APP would cost over £200 though with no guarentees that it will fix the fault.

...(he described it as a carbon runner)...

...ie a form of potentiometer.

These sometimes do go wrong with use, it's common practice in electronics to spray them inside with contact cleaner, just to be safe.

To actually relace the TPS and the APP would cost over £200 though with no guarentees that it will fix the fault.

Alex, if you know the part numbers or can post an EPC diagram showing the parts I can check price here for you IYW.

specifically he has fixed 'many' Mitsis / BMWs by replacing a TPS located on the accelerator pedal assy, (hes learnt that its this one that is more likely a culprit than the one at the actual throttle body) I stress that hes not had to deal with this problem on a Supe, but he seemed to suggest that a pedal mounted sensor (linear, prone to wear / dirt) was more likely to play up than a stepper motor sensor that just takes current....by now youl have realised that Im not technical, but if there aint a sensor down there (like some BMWs) sorry for the red herring

It sounds like a diffrent set up to the supra. I think the more modern systems do away with the cable from the pedal to throttle body. Unlike the supra which keeps it as back up, and has the sensor fitted at the throttle. I could understand a sensor in the foot well getting dirty, and damaged by stray feet etc..

Alex, if you know the part numbers or can post an EPC diagram showing the parts I can check price here for you IYW.

Will do

if you guys revisit this thread.....Ive already splunged out for a new TPS @ £250 fitted, which hasnt worked and I would have twigged that if Id searched older posts better !...No Alex, I havent tried a Toyota dealer for diagnostics, simply because my local Toy dealer said it wouldnt work on an import !!! Toyota UK Cust Care say this is not accurate info, so your local may say different.....Im tempting fate here, but it hasnt happened to me since my last post and spookily, not since I put the original air-intake back on - all in the mind perhaps, but (auto) changes seem more sensibly timed now as well....(ref problem always happening when in traffic etc) surely heat soak / Blitz Sonic wouldnt domino signals from odo / speed sensor etc etc ?

Hi Ewen,

I'm in the process of fitting an entire replacement (used) Throttlebody and intake plenum. It's not been messed about with and should just work (lol)...If it works ok I'll then try changing my Throttle etc to be setup exactly the same...or find out which sensor is faulty.

The heat issue is interesting....but really the intake charge on mine should be fine...got an FMIC in the way (the rad might not be happy but the intake should be reasonable).

I've changed the throttle and gained absolutely nothing

It still wigs out and it still doesn't start properly when warm.

S**T!!!

Going swap the Throttle's back (and send Jake's back to him - thanks for the loan buddy you're a star) and take it Toyota. For diagnosis.

Hi Alex, wasnt sure wether to post this as it aint exactly sientific) but it hasnt happened again since 22nd of Jul when I put the original air-in box back on.........Ive kinda been trying to make it happen, lots of stop-start traffic, fast back roads home then pootling round town, junctions, traffic lights etc, even (deliberately) joined the usual A31 (Ringwood to Poole) traffic jam last Saturday to see if on-off light throttle would trigger the fault - absolutely fine and not a sniff of hesitation or dodgy auto changes....I havent removed the speed converter / delimiter yet (for process of elimination) as I want to know if the standard air-box / Blitz sonic issue is remotely feasible (re-cap - it never happened for the first year / 10k, but started not long after the Sonic was fitted, and hasnt happened since the Sonic was taken off). It may never happen again, but if it does Ill go from there....

OK that's good news for you.

Now the bad news...I have a Single Turbo conversion and cannot use the stock airbox

I've always associated it with heat soak....and thinking about it, it might have gotten worse since the latest filter was attached (it's a bit small for my liking). If only I could just test your theory without masses of work/fabrication....

Hi Alex, Im flattered you call it a theory ! Im actually in denial....far easier for me at this stage to swap intakes than diagnose converters / dry solder etc etc...Im the sort of guy that swears the car goes better after its been washed, more a state of mind than technical confidence...so far so good for me, hope yours is sussed soon

OK that's good news for you.

 

Now the bad news...I have a Single Turbo conversion and cannot use the stock airbox

 

I've always associated it with heat soak....and thinking about it, it might have gotten worse since the latest filter was attached (it's a bit small for my liking). If only I could just test your theory without masses of work/fabrication....

a while ago i watched the stock ecu (non vvti) lean out the mixture when air temps got around 55 deg. this didn't happen under boost though. i don't know much about the vvti but i bet your problem could be after stopping the bay temps raise and the car is trying to start with an initial gulp of very hot air which would make the ecu lean the cranking mixture.

I wonder if i disconnect the intake temperature sensor, will it fire at all? If it does does it assume it's cold? Does it assume it's hot?

This is the problem with the all too clever FBW throttle....I'm guessing it won't work without all the sensors in it connected.

Wonder if I can cool this area too like the intake...can't really lag it away from heat sources...

i know mine wont start without the coolant sensor connected