Code 51, and TPS question.

[Adam M.]

My sons Supra works crappy and shows code 51.
I read it shows AC problems and TPS problems.
AC was taken off this car, should I still suspect TPS / wiring problem ?
Is TPS from turbo car identical to non turbo car ?
Sorry for perhaps naive questions, but I'm just starting with learning 7M-GTE.

 

[lewis15498]

Even with your ac removed code 51 will trip if you the ac button on the climate control is turned on. Judging by its running crappy, I would say its tps related. I'm like 90% sure ge and gte are interchangable, however I think they also changed between years.

 

[gaboonviper85]

Odds are you need to adjust the tps or get a new one...they aren't that expensive.

 

[lewis15498]

All NA supras use the same TPS. Turbos used a different TPS up until march 1989. Turbos manufactured after that date used the same TPS as the NAs. The sticker in your door jamb should tell you when it was made.

Can you use an NA TPS on a pre 89 turbo? I dont know, I'll let someone else chime in here.

 

[lewis15498]

Odds are you need to adjust the tps or get a new one...they aren't that expensive.

Yeah theyre not that bad. TPS wear out over time, its not something that either works or doesnt. Id just get a new one, that is assuming you need one.

 

[Me[kk]A]

Hey guys, Im the son with the supra
just curious about a few symptoms.

The wierd thing was that prior to us fixing an intake manifold gasket, the car ran better. Once we fixed the vaccuum leak the car ran marginally worse. The car seems very rich, you can def. smell fuel. It does not want to stay on while cold so we have to keep the throttle going. If we let her idle, she glugs down to about 200, then revs from 100-200 a few times then dies.

Once warm the engine still runs rough and the idle still jumps. Would a bad TPS cause all of this or should there be other things i should consider?

 

[IwantMKIII]

Welcome to the boards but you need to learn how to use the "search" button. This topic has been well covered 10000000 times.

Your TPS is out of spec for its idle voltage read by the ECU. In other words, it's not properly adjusted to let the ECU know your foot is not on the throttle.

 

[3p141592654]

TPS won't cause car to run rich. A hint: code 51 is usually caused by a maladjusted TPS, and that signal tells the ECU to go into idle mode. Your car shows poor idling characteristics, maybe there's a link, do you think? Don't waste your time replacing it, when all it probably needs is an adjustment.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=101

 

[IwantMKIII]

TPS won't cause car to run rich. A hint: code 51 is usually caused by a maladjusted TPS, and that signal tells the ECU to go into idle mode. Your car shows poor idling characteristics, maybe there's a link, do you think? Don't waste your time replacing it, when all it probably needs is an adjustment.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=101

You may want to rethink that statement.

 

[3p141592654]

Oh really?

 

[lewis15498]

TPS won't cause car to run rich.

You may want to rethink that statement.

Oh really?

Really. TPS resistance decreases with throttle increase. When TPS wears out the resistance of it decreases. Because of this your computer thinks its getting more throttle than it really is aka rich condition.

 

[3p141592654]

AKA no such thing. I have disassembled the ECU code. Your car computes fuel primarily from the AFM and RPM. Everything else is a correction. TPS is used only for transient throttle events. Don't believe me, disconnect the VTA signal wire and go for a drive. You will not run rich, you won't even know its disconnected because it will drive normal. Most of these cars no longer even have a good VTA signal due to flatspots worn in the TPS potentiometer trace.

 

[IwantMKIII]

AKA no such thing. I have disassembled the ECU code. Your car computes fuel primarily from the AFM and RPM. Everything else is a correction. TPS is used only for transient throttle events. Don't believe me, disconnect the VTA signal wire and go for a drive. You will not run rich, you won't even know its disconnected because it will drive normal. Most of these cars no longer even have a good VTA signal due to flatspots worn in the TPS potentiometer trace.

Im well aware of the fact a TPS can be disconnected and the car can be driven. It would be a poor design if it didn't. Try resetting your ECU and disconnecting the TPS.....maybe then my point will be made. Try resetting your ECU and adjusting your TPS out of spec (as this is mostly what happens when TPS's go bad), find out how great it runs.

 

[Me[kk]A]

So we confirmed last night that the TPS is shot. We also still have a leak on the intake manifold side still so i'll be tackling the injector O-rings next.

Thanks for all the assistance thus far!

 

[jetjock]

In the interest of accuracy I'll say there are people in this thread who have NFI what they're talking about but 3p isn't one of them...

 

[3p141592654]

Like I said, its not used for anything but transient fuel calcs. The ECU does not check that the TPS signal is valid, and resetting it will not make any difference. There are no error codes for the TPS except for the IDL signal, which is the only signal from the TPS that will actually make a significant difference to driveability. Please stop posting your armchair theories.

 

[jetjock]

Well, there's code 41 Jon. It can be set by three situations, all of which involve VTA. That said as long as the load and rpm signals "jive" you're correct in there won't be permanent enrichment. In other situations there will be. For example if VTA is maxed at idle CO will rise to around 6%.

The "ECU resetting" thing needs to die though. It's pretty clear the majority here don't understand what it's about...

 

[Me[kk]A]

Im completely new to Supras. Im used to hondas. Im learning about this car as I go along and its been a mess of a process. It seems she ran better with more issues than currently as ive fixed them.

my biggest concern currently is the idle which i pray another TPS with the adjustment done correctly will help.

Im also fixing the oil return line to the turbo, replacing the current wastegate as it is not holding pressure and going to be running another wiring harness to clear out the mess that is currently half the problem.

I remember reading that the supra used to have an issue with cold starts and running badly which an ecu change fixed. Is this a common issue for the 86-88 (yellow plugs) ecu? would an upgrade to an 89+ harness and ecu solve this?

my mileage is also horrible lately.. under 300 kms for a full tank of 94 octane fuel.. hoping finally fixing the vaccuum leak, wastegate, tps will help in this area.

 

[3p141592654]

Damn, Gary's keeping me honest. I forgot about 41, fair point, and the WOT open-loop trigger will impact mixture, but driveability will still be good. I doubt he has a 4-gas analyzer! :icon_bigg

Anyway, back on topic he doesn't have a code 41, so its moot. 51 needs to be fixed first, so adjust the TPS.

 

[Me[kk]A]

Damn, Gary's keeping me honest. I forgot about 41, fair point, and the WOT open-loop trigger will impact mixture, but driveability will still be good. I doubt he has a 4-gas analyzer! :icon_bigg

Anyway, back on topic he doesn't have a code 41, so its moot. 51 needs to be fixed first, so adjust the TPS.

pickin up the tps tomorrow, along with all new injector o-rings and grommets for the intake manifold. pray for me gents.