Topic: TPS problems

[bluetoy84]

 '89 22RE  Here's the problem : cranks and idles fine ,but as soon as you move the throttle it won't rev it just starts loping , if I unplug the TPS it will rev just fine. I replaced the tps with one that I thought was good and it didn't help , it still won't rev with the tps plugged in . Is my problem with the throttle sensor or could it be somewhere else. Any help would be greatly appreciated. Thanks!

[BigMike]

Maybe a third opinion from another tps sensor?

It's hard to do with a multimeter (if you have a meter that graphically displays voltage vs. time then its simple) but hook the volt meter to your tps and slowly move it by hand. It should slowly grow in number linearly without any peaks or zeros. I believe its the 2nd wire and the last wire (out of four), if your looking at the plug with the tps upright. Use your ohm setting to see the resistance between the two wires.

This is the typical ways that TPS sensors go bad. It's just a potentiometer and sometimes they get worn out on one certain spot, and while you're driving when your pedal is just in the spot it will run funny....................But.....................if this was the trouble with yours, it would still rev just fine, it would just have some minor problems while driving or something. So Im guessing its something else but I dont know.

When you say its going into loop mode, how do you know this? Is it reving slowly? higher idle? Has the ecu thrown any codes yet?

Good luck-
BigMike

[bluetoy84 [OP]]

I know I should have ran the trouble codes from the ecu first, but I didn't have my list of codes handy and I did have a spare tps .I'm beginning to think I have a loose connection somewhere other than the tps. Is there any other sensors that would directly affect the tps? Also I didn't mean that it was going into loop mode , I meant that the engine was loping ,revs to about 1200 then almost dies,revs-dies, revs-dies, revs-dies, (you get the point) sorry for the confusion. It runs just fine with the tps unplugged it just idles too high and don't have any power. I'm lost ,all my junk is carbuerated this is my buddy's truck. Anyways , I'll run the trouble codes when I get home. Maybe it will point out something I missed. thanks for the help!

[BigMike]

I meant that the engine was loping ,revs to about 1200 then almost dies,revs-dies, revs-dies, revs-dies

Ahhh, now it sounds like you've got a vacuum leak, possibly between the throttle body and the air flow meter, or your air flow meter is junk.

That's cool that you're carb and your helping out your buddies efi. Efi's are pretty cool and its always nice to learn about 'em. Kind'a the same way with me, I dont know jack squat about how to trouble shoot carbs and I wish I did.

The term 'loop' is actually a programing term that we use to describe the behavior of the computer itself. Before the engine warms up, the computer is in what we call "Open-Loop Mode" where it is monitoring all sensors and checking out the air temp and oxygen content, etc. Once the engine warms up, the engine revs down to normal idle, and this is because the computer has just switched into what we call "Closed-Loop Mode". Now it is operating within a preprogrammed set of preferences with considerations for optimum power, gas mileage, and lowest smog levels.

So when something like a sensor is really screwed up, the computer will stay in Open-Loop mode because it sees a problem and will not operate normally and will avoid closed loop mode. So the power would be off, the mileage would suffer, emissions could be worse...... basically the computer waits for a 'all systems go' condition before it runs closed-loop mode and before it's gonna run normal.

Sounds like a barrel of fun doesnt it?

[bluetoy84 [OP]]

Found the problem! Ran the trouble codes and the only code it give was for the tps, so I found a third one and tried it.  I also found a loose ground wire , near the alternater . Is there any way that a loose ground could have been toasting the tps? Don't know , just glad it's running. I'm about to learn a lot more about EFI . I'm starting an EFI conversion on my 84 this weekend. I have the complete wiring harness and EFI setup from an 89 4-runner. I'll start a thread on it and let everone know how it goes, plus I'm sure I'll have a few questions. Thanks for the help!!!

[GrimReaper]

Did you make sure that you set the TPS right? Is IDL and E2 are not making closed at Idle it will cause the idle to surge or even stall when the brakes are pressed (the ECM monitors the brake light switch as well).

Roger has some good information on his site on adjusting the TPS and checking the AFM.
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

here are a couple FSM for the MkII and MkIII Supra. A lot of stuff like the AFM, TPS and general trouble shooting are the same. The codes won't be and the MkIII uses a IAC but the FSM trouble shooting list is great and valid for diagnostic.
http://www.cygnusx1.net/supra/techtips.html
Between that and a Haynes or a Chilton's your set. The W58 used in the supra is nearly Identical to the W56 in the truck. Only big difference is the tail housing. I used that MkIII transmission section when I rebuilt my W56. It was spot on.

[bluetoy84 [OP]]

Thats some good info on adjusting the tps. I'll try that . Thanks !!