TPS problems again...

Intothenight19

Intothenight19

Crissaegrim
Feb 23, 2006
221
0
0
Pa
So I went to re-calibrate my tps sensor with the help of a friend and a nifty snap-on voltmeter. And after a while of trying to re-calibrate the sensor I plugged it in and went for a drive. In first gear I almost get to about 2000rpms then the engine cuts power, I dont mean it shuts off, it just gives me no fuel, almost goes into a limp mode. Then seconds later it accellerates again but only to 2000rpms then falls on its face. I am using a JDM throttle body and the sensor that is on it has a blue toyota/denso sticker and the inside is straight up and down. Now, the old throttle body that was on my car used a tps sensor than was horizontal, could it be the computer only recognizes the pre-89 throttle sensor? Im clueless because it runs fine without it plugged in.....Any ideas, thoughts,suggestions are welcomed! Thanks
 
Intothenight19

Intothenight19

Crissaegrim
Feb 23, 2006
221
0
0
Pa
Jetjock thank you, finally a real answer. So should I get a new sensor? The no-linkage throttle body is great and I'd rather not scrap it, will the computer recognize a sensor from a different year?
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
Well, it's only a guess based on what your describing but since you were messing with the TPS it's a good bet your problem is rpm cut. That said if you "calibrated" it right you shouldn't have this problem. Also, 2000 is a bit low for rpm cut.

If it is rpm cut what's happening is simple. The TPS has a switch inside that is turned on at idle. This is how the ECU knows the throttle is closed. The ECU also knows engine rpm and the amount of air coming into the engine. If it sees rpm and airflow increase while the idle switch is closed it knows something is wrong because that situation should never happen. It says "wtf!" and shuts off the fuel at around 2500 rpm. As soon as rpm drops to around 1500 it turns the fuel back on. A sure way to check this is to bring the rpm up in neutral and see if it cuts off. If you can put the pedal to the floor and have the engine cycle on and off rpm cut is the culprit. It's all in the TRSM.

A second way of checking is to jumper the diag block and see if you have a code 51 with the pedal pressed. If you don't the idle switch in the TPS isn't opening and rpm cut will be active. A third way is to simply unplug the TPS and see if the problem goes away. (Oh wait, I see you've done that).

If all that happens put the proper part on and adjust it. The idle switch needs to open as soon as the gas pedal is slightly pressed. Do it per the manual or use code 51 as a quick method ie; you shouldn't have a code 51 with the throttle fully closed and you should have it as soon as the throttle is cracked. You should also compare resistances of the TPS you're using to the specs in the manual. If the ones marked "VTA" are not the same you can't use it.

Finally, there are two p/n TPS that I know of that will work on the Supra. One is 89452-28030 (the stock one) and the other escapes me at the moment. I know it's a 89452-280XX though. Perhaps someone will chime in.

Edited: Due to technical brain fart.
 
Intothenight19

Intothenight19

Crissaegrim
Feb 23, 2006
221
0
0
Pa
Great response man, its the info I've been looking for. So you think I should replace it? I bought the one I'm using now from a member on the forums, he said it was in good working order, maybe Im just doing things wrong, I tried to set it per the TSRM. The resistances were just not equally out...Hmmm.. Maybe its fried? Again, thanks for the info, any more advice is greatly appreciated, as I feel I've hit a dead end.
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
It's easy to check so I don't see what the confusion is. If the resistances don't check out per the manual replace it. After you do, set it up as I described above or use the manual. All you're doing is setting a switch to have continuity when the throttle plate is closed. It's not rocket science.
 
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