TPS adjustments, unclear on voltage readings.

[Nathaninwa]

Long story short....new registered member, but not at all new to the Supra/7m series engine scene. There is so much info that searching can usually find what I need. About 3 years ago I installed a 7m into my trail truck with a Cressida harness and ECU. Got it running and more or less drove it, but has always felt like its been down on power. So recently I have installed an 87 MT supra ECU, made an adapter harness from the old style plug to the newer style grey plug by sacraficing a spare ecu I had. Now I am going through and verifying all the info i can. Ive come down to the TPS....NSW/AC....and the speed signal

My questions.....does the ECU need to have a NSW signal and an A/C signal, or will this just pop a code 51?

Does the ECU use the speed sensor signal for any fueling/timing adjustments?

And I have adjusted the TPS according the to the online TSRM ( http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=101 ), and all is within ohm spec at all points. But when it comes to checking voltages I have a problem. My information comes from ALLDATA. 87 supra 7mge should read 4-5 volts at wot on VTA, and I get 3.6 volts, no matter what tps number I am using. And I am supposed to get 10-14 on the IDL pin at WOT and I get zero.
In reference, the 1990 Cressida ecu wants 3.2-4.2 at the VTA, and 4-6 volts on the IDL pin.

I can adjust the tps to read 4.1 volts at WOT before the voltage drops out to zero, but then idle is way off....and neither option gives me 10-14 volts on the IDL pin.

I have not tested the Cressida ECU, only the Supra as I am wantring to get away from the auto ecu setup, and possible power downage from improper inputs on the tranny side, and possible no VSS signal.

Im working some other kinks on the truck before I can drive it, just wanting to solve the voltage questions on the ECU before I button it all up.

[Nathaninwa]

I should say that the truck does run....had a 51 code when I first started it, then when I was tweekin I was checking the VF voltages and tracking the afr with a narrow band guage....I found out more like the fpr was a turbo model, not an NA, base timing was off 5*, and other small things. I need to do a fuel pump before more testing can be done, and i want to build a little larger intake tube over the one I had. Ive done so much testing with different tps numbers, I have kinda forgotten what is what. So I found a guy parting out his 87 NA MT supra and bought the fpr, ecu and matching tps. The number is gone so I am not sure which one it is, but I do have a 28030, 14050, and a 20050. None make a difference at getting the WOT voltage on the IDL or the VTA wires.

Just curious if this will make a difference at all, or if just driving it, and as long as there is no code for a tps Im fine?

Ill be welding in a wideband sensor bung and tuning the afm via that, and to have a better idea of whats goin on.

Im so used to hooking up a laptop to my cars. I have a 501whp Volvo 940 with a stroked 2.5l 16v motor that I adapted Eclipse enging managment onto and running DSMLink (ECMLink V3) on speed density.

[Nathaninwa]

I have done some more google searching for IDL voltages. Reading on several forums, 3.5 volts is common on the VTA for wot throttle for all engine, and the IDL voltage at wot being 10-14 volts might be a misprint in the books brought over some of the earlier efi systems. Its supposed to be 5 volts at wot, but I dont get that either.

Ill check today with the 4 tps's I have. I know all sweep from .0x voltage at idle to about 3.5 when adjusted on the TB on the VTA wire, but can reach 4 volts when the sensor is spun by hand......Ill check for IDL voltages, what they are at idle, make sure it gos to zero, then should read 5 volts or so at wot?

I wonder if a problem could be I dont have the NSW hooked up to the ecu? Looking at teh schematic, looks like I want to supply 12 volts positive at idle, or any point the clutch is not depressed?

[Nathaninwa]

Just searched out that the nsw is 12pos only when the clutch pedal is depressed. So I'm chasing at this point if I really need 5 volts to the ecu on the idl pin at wot.

[87hilux7mge]

i would offer an opinion...but thou art far more versed with this situation than i am! when it comes to wiring, i cant tell a wire color from my...well you get the point.

personally re-wiring for ecus always scared the hell outa me, and something always ended up not working.

but props too you for doing what youve done!

[Sonyps307]

I was having the same proble with the wot. I would get 3 volts at like little less then 3/4 throttle and then 0 at wot. Then I found out that I was calibrating it wrong the way tsrm shows is to test it. Read this link and do it his way should help.


http://mkiiisupra.net/bbs/showthread.php?t=12132

[Nathaninwa]

Thanks for the link....I had acutally read that before with all my searching. So today I cycled each of my TPS's quite a few times....must have done something because they all seem to work now.

When all are calibrated properly, Im seeing between .5 and .8 volts on the VTC wire at idle, and close to 3.6 volts at WOT with a smooth curve inbetween.

I also figured that Toyota is using the absence of voltage for its idle circuit. When ohmed out properly with feeler guages, I get near .5 volts at idle, and anything above that is 5 volt reference now. All my tps's read the same, regardless of part number. So I am getting my WOT throttle voltage, and hence why there is no voltage check at idle, only wot.

Ill do some more seaching, but I just need to figure out what the ECU uses the speed signal for. Its generated on the back of the cluster and gos to the cruise and engine ECU's. I have found one reference that it uses it for "some ecu functions"

[Nathaninwa]

More research on the VSS signal, shows that the ecu uses it for optimal timing and fueling based on rate of speed change....so it is important for me to find and hookup the signal.

[cre]

Vc should be between 4.8v and 5v.
VTA should range from .5v (as low as .4v is fine, IIRC) to 3.48v (higher than 3.48 may result in a fault code depending on the actual tolerance of the components in your specific ECU).
Vs should range from .4v to 4.8v.
IDL should be 0v with the throttle pretty much closed... otherwise it's an open circuit... should be around 5v, but it's irrelevant.

I presume that by Vss you're referring to Vs or the VAF signal input? Yes, Vs is used in most calculations as long as a valid signal is present... after an out of range signal is diagnosed by the ECU it will revert to a base map, but you won't like it.

Also, the ECU does need a signal from the stock oil pressure sensor (in case you don't have that connected either)..... god I hate these hack jobs... full swap or standalone any day please.

Did you also swap in the N/A Supra's intake plenum and get the ACIS system functioning?



BTW, what injectors are you running? There's no practical way to run the low impedance injectors used in the older 7Ms on the newer revision 7M ECUs; There's significant latency introduced and flow is erratic at best if you try simply wiring in load resistors. Now the other way around well, it works fine but I don't know why you'd ever want to (peak and hold injectors are far more readily available).



EDIT: And damn... if I had a nickel for every time All-Data was wrong about something.... well, I'd only have about a handful... but the point stands that I'd still have a handful.

[Nathaninwa]

Thankyou for the reply. In the beginning I was trying to have just a stock running engine, turn key, no problems. It has ran for 3 years this way, just down on power. I have thoughts of the DIY pnp megasquirt, but the cressida harness plug is not avaialble, however the earlier supra model with the yellow plugs is, so rather than spending a ton of cash on MS I thought I would start with the supra ecu since I needed to make an adapter harness anyways. So megasquirt is in my future, just toying with this route first.

I don't have the NA intake....the cressida was setup to run the GTE intake, and from what I have read, the 86/87 supras ran the GTE intake as well, so no wiring for that is avaialbe.

Ill look tonight, but I don't remember seeing an oil pressure input for my model year ecu.

I was refering to the vss, or the speed sensor....looks like that is an important ecu input.

All the readings ohms/volts specified are within spec on the afm and tps circuits now.

I should note, that tho I have not started it yet.....with the codes cleared in the ecu, I can work the throttle, and afm, recheck for codes and don't get any. I'm reworking my intake pipe and need to get the new fuel pump in...by the weekend I should be started back up.

And I'm runnning the later model high z na injectors.....they are wired into my early ecu without a resitor pack. So I have the 315cc green tops vs the 295cc low z yellow tops.