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Old 06-04-2012, 01:44 AM   #1
1989toyotasupraandpickup
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Default TPS voltage problem

So here is the story. i own a 1989 toyota supra turbo. the problem i am having is the voltage at idl and e2 at the ecu. When i probe these leads i get 10 volts instead of the 4-6 that toyota calls for. when i unplug the ect for the transmission the voltage across idl and e2 drops to 5.2v. this is where it is supposed to be. Anyone know what the problem may be.????? please someone help i am ripping my hair out wondering where the problem may lay. thanks
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Old 06-04-2012, 11:27 PM   #2
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Anyone??????
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Old 06-04-2012, 11:44 PM   #3
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if its faulty, replace it bro
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Old 06-05-2012, 03:27 AM   #4
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thats the thing i dont want to pay for something i dont need. im going to run it how it is. it runs ok just runs rich but that may be because i had the battery disconnected for a few days. only had it idle in the garage. the computer needs to relearn the fuel pattern.
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Old 06-05-2012, 07:55 AM   #5
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Measure the resistances across the TPS connections as detailed in the EFI section of the TSRM. Disregard the info you have concerning the voltage, if you look in the ECT section of the TSRM you'll find it specifies approx 4v.... The ECT computer pulls the voltage down, a manual equipped 7M should have 10v to 14v. It's pretty broad as it's not there to give any signal beyond on/off.

A bad IDL switch isn't going to cause you to run rich either.
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Old 06-06-2012, 04:37 AM   #6
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thanks cre. what would cause the car to run rich?
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Old 06-06-2012, 08:26 AM   #7
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There are many, many possibilities... More than I feel inclined to just blindly list off.

When is it running rich and how did you test it?

Are there any diagnostics codes stored (or were there before you disconnected the battery)?
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Old 06-07-2012, 04:25 AM   #8
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its running rich on idle. before the i replaced the manifold gaskets at idle the car would run at 14.7 on the afr gauge. now that i put it back together i find that the car idles at around 12.5 or so. no codes that i have found but the check engine light will not light up if there is a code. it does turn on when i turn the key to the on position indicating that the light works. i have to jumper the terminals in the diag box to find if there are codes. really weird. my truck is the same way. but i think i may have found the problem. it may have been a broken signal wire to the oxygen sensor just off the down pipe. its a shielded wire. i fixed it and put a new connector on and decided to replace the main front crank seal seams i have it all ripped apart and the old one was dry rotted. i will have it running by tomorrow hopefully.
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Old 06-07-2012, 04:37 AM   #9
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Originally Posted by 1989toyotasupraandpickup View Post
its running rich on idle. before the i replaced the manifold gaskets at idle the car would run at 14.7 on the afr gauge. now that i put it back together i find that the car idles at around 12.5 or so. no codes that i have found but the check engine light will not light up if there is a code. it does turn on when i turn the key to the on position indicating that the light works. i have to jumper the terminals in the diag box to find if there are codes. really weird. my truck is the same way. but i think i may have found the problem. it may have been a broken signal wire to the oxygen sensor just off the down pipe. its a shielded wire. i fixed it and put a new connector on and decided to replace the main front crank seal seams i have it all ripped apart and the old one was dry rotted. i will have it running by tomorrow hopefully.

The AFR will be around 13, maybe a little richer, when the ECU is operating in open loop (cold starts, bad ECU temp sensor, bad TPS signal, no OX signal, etc).
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Old 06-07-2012, 07:59 AM   #10
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ya thats what i was wondering. it could be that broken wire to the oxygen sensor. the tps sensor is within spec that the manual gives. ecu temp sensor is brand new and test out ok. it has to be the bad oxygen sensor wire. what causes the cel to not come on when i have codes but does only shows the engine light when the diag box is jumped??? Appreciate the help cre and everyone helping
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