code 51/ quits when returning to idle

[professorbob]

The relay check OK as per the manual... Decide to check values on the fuel pump resistor.... should be 0.70 ohms. Resistance is 1.4 on the 200 scale. Thinking this may be my problem, as it will not allow the pump to spool up as rpm increases.
Is there a method for direct wiring the pump relay to bypass the resistor in order to determine if this is causing the engine problems I am experiencing?
When sourcing a replacement resistor. Is the turbo GTE unit different that of the GE engine type.

Thanks
Prof.

[cre]

The resistor is employed at LOWER RPM and load... not where you're experiencing the problems and it's not bypassed by the relay until around 4K at a medium or higher load, IIRC.... Besides, with higher resistance on it you'd be running lean, not rich. Do keep in mind that resistance varies depending on temperature too... but yes, that is a good deal higher than it should be.

You can bypass both relay and resistor by unplugging the large, round, yellow connector and jumpering the Blue wire with black stripe and the black wire with red stripe. Use heavy gauge wire.

The GTE and GE resistor packs should interchange just fine.

[professorbob]

I ohm ed out the TPS. The throttle stop screw is not touching the rocker and there is about 1/16 inch of distance between the two in the completely closed position. The stop screw is seated against what I believe is the dash-pot diaphragm though.
The value is within speck in the completely closed but I was unable to set the feeler gauge for the two lower settings.
However the WOT Wide Open Throttle position has two reading and one is way out of scale.
I am wondering if this may be a contributing factor.
I expect at this point it would be OK to reinstall the header gasket to be able to operate the engine to establish another code set. I cleared the codes by pulling the DOME 20 fuse.

[cre]

The engine should run fine with the TPS disconnected... it may have some trouble transitioning into idle and with tip in/out response. A bad TPS should have VERY little effect on the operation of the engine; It is only a trim sensor.

[professorbob]

I have an indicator that is on that I have not noticed before. It is extreme left on the dash beside the temp gauge. Looks like a radiator with the cap above or something similar. Can you tell me what it indicates.
Thanks
Prof

[professorbob]

I reinstalled the exhaust header gasket and ran the engine to create codes. Started engine and allowed it to reach normal operating Temperature. RPM was still up when I pushed the accelerator pedal and it dropped back to about 800 which is in range. Slightly rough idle probably because of the excess soot. Tried to increase RPM and it would work up to 2800 quit until it dropped back to 16 1800 then come back up to the throttle position of 2800.
Shut it down and checked codes. 41 Throttle Position Sensor TPS... From your previous post about being able to run the engine without the TPS, I unplugged and restarted the engine. With the TPS disconnected I now am able to get the engine to reve to 3500, although still a little rough, which indicates the TPS may be the main problem here. I did not want to go any higher on the RPM without a load on the engine.
Question. Will an aftermarket TPS work, or should this unit come form Toyota. Thanks for your input in the search for my problems.

Also still wondering about the light on the dash as per above.
Thanks
Prof.

[cre]

The lamp you describe is the 'low coolant' light. The sensor is in the reservoir... not really the best indicator if the whole system is low, but it's better than nothing.

Code 41 mean there is an actual short or a break in the circuit. While the TPS being 'out of whack' shouldn't cause significant drive-ability or operation issues a short most likely will. A removed TPS will create rough transitioning when abruptly revving the engine, transitioning to idle and may affect WOT performance at lower loads; Smooth transitions in throttle shouldn't really see rough operation. This code will set and remain stored if the TPS is unplugged... Are you still getting this code after a reset? (Without looking at my notes I believe) TPS signal (VTA) should read >480mV at full stop (closed throttle) and ~3.48V at WOT.

You could install a universal unit but you'll probably need to add a separate IDL switch and you'll also need to verify that it provides the voltage as detailed above and not a 0V to 5V signal... On top of adapting it to physically connect you'll want to consider that when deciding if it's worth it. I rather like converting over to more readily-available and common components on rarer vehicles... like GM knock sensors.

Is the harness unmodified or has it been modified or shortened/lengthened at all?

Check your grounds, specifically E1 and E2. Also check Vc (should be ~4.8V at the TPS and AFM harness connectors with the ignition on or the engine running).

[professorbob]

Thanks for the rapid reply... I have the front of the vehicle on jack stands, and this may cause the coolant to be off the sensor. I'll check it and add coolant as required.
Regarding the aftermarket TSP... I would rather keep the vehicle as near authentic as possible and was not intending to us a universal unit, but a OEM type replacement just not from the dealer because of the extra expense. This vehicle is all original and has not been modified.
I will check NAPA or O'Rileys to see what they have specifically for this year model. Some suppliers carry the denso units.
Reference the ground check.
Check your grounds, specifically E1 and E2. Also check Vc (should be ~4.8V at the TPS and AFM harness connectors with the ignition on or the engine running).
Are you referring to the TSP harness plug, or at the Code reading terminal?
Unplugging the TSP stopped the cutting off at 2500 RPM and I could increase from Idle to 3500 with no hesitation. Just got to think there is a problem with the tsp circuit.
How would one go about checking the supply harness to the TSP. It has not been changed in any way.

Now that I am able to get the engine to act somewhat normally, and because I replaced the original MAF Karmon vortex sensor with a used unit not from the 89 model year, I am going to reinstall the original unit to see if that improves/or not the over rich condition.
I have read that the wrong MAF sensor can cause an over rich condition.
Your thoughts?

[cre]

Points of clarification: It's TPS, Throttle Position Sensor; The 7M-GTE is paired with a KVAFM or AFM for short, Karman Vortex Air Flow Meter. The 7M-GE uses a VAFM or Vane Air Flow Meter (again AFM for short). A MAF (Mass Air Flow sensor) is a different type of device altogether... similar function just operates quite differently. (So many different devices.... such high prices for some and insane complexity with others really make me sooooo happy that there are even piggybacks out there which allow us to convert from one type of air meter to something cheaper or larger or more reliable such as a 3.5" GM MAF, GM MAP / IAT setup and so on).

The AFM did not change for any year; So unless the AFM you've installed is from a different vehicle the only thing which would cause any change is if it is in fact defective. I can't say it would be the first time I've heard of someone going through two (or five) only to find they were all bad. Now if you're referring to the Lexus 1UZ KVAFM then yes... BUT the electronic part of the assembly is still compatible, only the housings are different. The stock housing is a bit smaller than the Lex AFM. If you have a Lex and the original on hand you can install your KVAFM test it out and then swap in just the electronics from the Lex AFM and give it a go.

What I mean when I say to check E1 and E2 is for you to check all the grounds at the head of the engine. There should be one group on a separate stud on the lower part of the intake plenum and I believe another on the exhaust side by the firewall which connects to a stud by the mounts for the throttle linkage assembly... although there may only be one ground going from there to the firewall. Clean all surfaces with some sandpaper. Check the engine grounds too while you're at it; The grounds to the block and the driver's side fender.

Vc is the voltage supply for certain sensors. You should measure it at the AFM's connector and at the TPS' connector. Really if something were wrong with this line you'd most likely be seeing errors for at least the TPS and AFM (and possibly some others depending on the nature of the problem) but it's worth checking to be sure.

The TPS is a wear component which ideally should be replaced every 75K to 100K miles. As it's just a basic trim sensor a lot of them end up never being replaced and as long as the IDL switch doesn't go bad they may never get replaced during the life of the car.... That should give you a general idea of just how important they are to the vehicle's basic operation. No there are circumstances where they may cause some significant headache such as a short across other circuits but more often even those are harness problems and not a problem in the TPS itself.

[professorbob]

Added water and the low fluid light went out. Still have not located the drip at the back of the engine, and I expect that is where the coolant leaked out.
Leaving the TPS Throttle Position Sensor disconnected, I started the engine and allowed it to reach operating temperature.
Decided to drive it down the street a few block to see if there is any difference in performance.
Still no joy. The car will with hesitation to accelerate ( probably because of the disconnected TPS) it shifted from 1st to second but faltered before being able to up shift to High.
Tried to go to WOT Wide Open Throttle and had very poor response and still not increase in speed. The engine would cutoff at 2800 rpm. and drop back to 1800 where it again would try to gains speed.
Still have the very high rich mixture, as there is huge amounts of black smoke, as one would have on a carburetor engine with full choke.
After about 1/4 mile, I returned to the garage to check codes.
Had a 32,41,51.
For sure the 41 is the disconnected TPS. 32 is the turbo, or AFM or ECU.
I certainly wish there were a way to check values on these Karmon Vortex AFMs to make sure they are OK. Trying to contact another supra owner to ask if he will install these electronic units on his supra to see the response.
Will continue to read the manual this evening about checking values with ohm meter.
I noted that in some cases a analogue volt/ohm meter is recommended. Is there any special reason that a digital meter will not work.
I removed the ground screw for the real passenger side strap and scraped the brass fitting and hold down washer. Also did the same thing for the grown strap coming off the battery on the drive side wheel well.
I re-tightened the intake hoses to make sure there are no leaks.
The turbo gauge needle is just below the 0 indicator and drops to -4 at Idle. Is this normal. What should I look for from this gauge during the test drives. Under what conditions will the turbo response and in what manner base on shifting etc
51 indicates an issue with the A/C. I have the off button pushed, but still have lights on the circulation buttons. Is this normal or not?.

I know this is a lot of stuff to read and absorb and I appreciate you willingness to off input.
Thanks
Again.
Robert