1jz TPS resistances? Cold start low idle, misfiring

[Z2TT]

Hi,

I've had a few problems with the idle speed on my 1jz-gte and cold start issues too, such as misfiring on idle that fixes when the TPS is touched, low cold start, car redlining at WOT at higher speeds and not shifting etc. I thought I might check the TPS resistances just to see if they are in spec. Going off the 2jz-gte values which should be the same as 1jz-gte but I wasn't able to find any service manuals for 1jz-gte cars.

TPS Seems to be the same part number was mentioned that they should be the same I'm just wondering if these are the correct values to work off or if anybody has any other test procedures that I can follow from service manuals of other cars let me know.



Before I began doing anything, it would cold start at 1000rpm, then after a drive it would be 700 or 600 rpm, if i give it a rev when warm it would get back to 1000rpm or so then slowly work it's way down to 700 and then begin misfiring, touching the TPS plug seems to change the idle. So I thought it would be something ISCV and/or TPS related.

First I swapped the ISCV over with a spare, so while i waited for the car to cool down i thought I'd check out the TPS resistances, could only find a guide for 2jz-gte.

I started by adjusting the stopper so that it's just touching on the throttle lever but not pushing it, so basically made sure throttle is 0%

Then I went by that table and checked following pins on the ECU plugs :

with throttle closed (0mm clearance on stop screw) VTA-E2 is 0.62KΩ so within spec I guess
0.54mm space - IDL-E2 is under 0.5kΩ so i'd say it's ok?, it's at 0.05kΩ
0.70mm space - IDL-E2 is Infinite Resistance.
Full Throttle - VTA-E2 is only at 0.94KΩ
Resistance between VC-E2 is 0.13kΩ (Couldn't find VC Pin so I assumed it was the VCC Pin on my ECU Plugs)

Now after few hours that car had cooled down totally, decided to start it up.

Car starts cold at 600rpm, idles very bad, once warms up seems to idle ok, consistent but feels rough.
Have tried 2 different ISCV's too, with first one it seemed to start up cold at 1000rpm but still seems low, the other one I put on there seems to start up cold at 600rpm I don't know if it's because of the iscv or because I adjusted the idle stopper screw. Would have expected it to cold start at about 1800rpm. I've checked the coolant temperature sensor resistance and readings are good, also checked the air temperature sensor too and it's good.

I don't know if the ECU uses the TPS feedback for idle control strategy which might or might not be why my ISCV doesn't seem to be doing anything on idle, but going by the table posted above the resistances between E2 and IDL seem to be in spec. Wondering what the VC-E2 resistance is for as mine seems to be quite off.

Also tried resetting ECU.

Any Ideas?

[Z2TT]

Started the car up this morning, cold started at 1500 this time, it seemed like the ISCV swap might have done something, worked it's way down to 600 in 2 minutes or so.
Cold started it later that night, but this time only 1000rpm and temperature was about the same as the morning too I think.

Anyway I've checked my TPS resistances again, this time on the workbench not through the ECU plugs, and they all seem within spec when I'm testing right at the TPS itself.
but when testing through the ECU Plugs, some of the resistances are out of spec, here are my results :



The last 2 tests show different results when tested at the TPS and at the ECU Plugs, when testing at ECU Plugs, resistance is lower. Any ideas on this one seems very strange.

[CrUZida]

Ignore the TPS resistances.
As long as the IDL to E2 contact is working perfectly, and goes open circuit when you touch the throttle, everything will work fine.

[Z2TT]

Oh ok, well IDL terminal has continuity to ground on idle and changes as soon as you press the gas.

But I was wondering, what about the variable resistance with different amounts of throttle, isn't that important too and at full throttle? I believe the ECU would use it for something?
I was just mainly wondering why the resistances are out of spec when measured at the ECU Plugs on my car and could it have an affect on performance or autobox shifting.
Just want to get it working to the factory specs.

[CrUZida]

From my watching of an o2 sensor, there are really only 2 points on the TPS.
One for 'cruise' AFR's.
One for 'WOT' AFR's.

At about 50% (roughly speaking) the AFR's will drop from 14.5 down to about 12 in almost a switch like fashion.

Most of the calculations will be done via AFM and RPM.

[Z2TT]

Cheers for that i was thinking it would have something to do with it.

As for the readings I'm getting at the ECU plugs, would you happen to know why they are lower resistance than what i get measuring right at the TPS itself?, At first I was thinking if anything,
it would be higher resistance if there was a fault somewhere in the wires, I'm thinking could some wire be shorting to another causing those low resistance readings where I get 1.8 kilo ohms on
those 2 last tests, just want to see if I can isolate the problem but don't know what could be causing it.

Thanks.

[CrUZida]

Are you testing it with the ECU plugs plugged in, or unplugged?
The test needs to be done with the plugs unplugged.
Doing it with them plugged in will give false readings.

[Z2TT]

I'm doing it with plugs unplugged, yeah I would have thought that doing it with them plugged in would be measuring components inside the ECU so which is why I did it with them unplugged.
So that rules out the problem, I'm keen to try anything out as the kick panel/glovebox is out so I can try whatever to narrow this down.

Cheers.

[RA35GT]

Disconnect both the ecu and the tps and then measure the resistance of the wire by itself?

(As well as measuring it between the wire and chassis, other tps wires etc.)

[Z2TT]

Ok then this weekend I'll measure

- Resistance of each of the 4 wires from ECU Plug to TPS Plug
- Resistance between each of the 4 wires and chassis
- Resistance between Each wire and each other wire.

I'll see if I can post some results and see if we can get anything from it,
might be able to find whats giving me these weird problems.

Thanks.

[Z2TT]

Hi

Just done the tests posting the results in few minutes.

Disconnected both plugs (TPS and ECU) and then did the tests, here are the results

1. Testing Each wire from the ECU Plug to the Body Ground

VTA - Ground = No Continuity
IDL - Ground = No Continuity
VCC - Ground = No Continuity
E2 - Ground - No Continuity

2. Testing resistance from wires to the other wires done at the tps
plug :

IDL - VTA = No Continuity
IDL - VCC = No Continuity
IDL - E2 = No Continuity

VTA - VCC = No Continuity
VTA - E2 = No Continuity
VCC - E2 = 3.44kΩ ----------> This Seems weird, does this somehow mean those 2 wires are somehow shorting together ever so slightly, surely it can't be a bogus reading on the multimeter.


3. Testing resistance of each wire from the ECU Plug to the TPS Plug :

VTA = 1.2 Ohm
IDL = 1.2 Ohm
VCC = 1.2 Ohm
E2 = 1.2 Ohm

[Z2TT]

Hi,

That 3.44k resistance reading I got was actually just the map sensor since one of the wires connects to it, so nothing wrong I guess with my wiring from the sensor to ECU.

Recently checked codes and got "Error 41" and that's a TPS related error, but as measured at the TPS readings at the TPS seem to be in spec, don't know why they vary a lot at the ECU
especially my VTA-E2 and VC-E2 tests are very different at the ECU plugs than at the Sensor.