think my tps sensor is going bad
07-07-2010, 12:23 PM
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think my tps sensor is going bad
hey guys, got a 88 toyota pickup 22re, and i noticed today that my idle while stopped at a light or what not, would go up and down up and down, im thinkin its the tps sensor, if it is the tps wheres the best place to get one at and what brand to get, if u guys think its some other problem im all ears
07-07-2010, 12:34 PM
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07-07-2010, 12:50 PM
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I'm a firm believer in going all OEM for replacement parts.
I would try cleaning your throttle body and MAF first.
When is the last time you did a full tune-up on the motor? Plugs, air filter, oil, etc...
Fink
I would try cleaning your throttle body and MAF first.
When is the last time you did a full tune-up on the motor? Plugs, air filter, oil, etc...
Fink
07-07-2010, 02:01 PM
#7
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If you think it might be the TPS, usually by disconnecting it will tell you. The idle should go up and even out. If it doesn't even out, something else is going on and the TPS is not creating the problem.
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07-07-2010, 02:02 PM
#8
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When i replaced my TPS a few month ago i found a new one on line for 65.00 dollars, plus shipping. It may not have been an OEM part, but its working just as well.
07-07-2010, 02:55 PM
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TPS is not causing this condition. Your idle is to high. This could be due to vacuum leak, low coolent,........ When at idle, TPS idl -E2 contact should be closed and when at normal temp the idle should not go higher then around 1100. If it does it starts hunting up and down. Your idle should be 700-800 rpm at operating temp.
I bet your coolent is low.
I bet your coolent is low.
Last edited by Flash319; 07-07-2010 at 02:57 PM.
07-07-2010, 03:04 PM
#10
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How'd you determine his idle's too high? Are you saying one won't get a "hunting idle" unless it reaches above 1100rpm? That's just not true.
07-07-2010, 03:55 PM
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How else can you make it hunt (bounce)?
I guess if you push open your AFM it will do the same (maybe never tried). This has always been my experience.
Idle contact closed + Operating temp + high idle = bounce.
Let us know another way, this will help in troubleshooting.
I guess if you push open your AFM it will do the same (maybe never tried). This has always been my experience.
Idle contact closed + Operating temp + high idle = bounce.
Let us know another way, this will help in troubleshooting.
Last edited by Flash319; 07-07-2010 at 03:58 PM.
07-07-2010, 08:12 PM
#12
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Maybe there's a technicality I'm missing, and maybe you'd care to elaborate with some details? But, what I mean is that I don't see that a hunting idle necessarily has to go all the way up to exactly 1100 rpm with a bad IDL contact to bounce....particularly if the IACV is operational and closed. If the IDL circuit is worn, it could vary in resistance just enough to make the voltage signal unsteady without ever reaching 1100rpm on the upswing. Before I replaced mine a couple of years, it didn't. Just a slight up and down wavy idle. As I recall, it went between 900-400 or so.
07-07-2010, 08:35 PM
#13
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BTW, a high idle bouncing can mean TPS. You said it can't. If you run a google or YT search, you will some people experience the idle reaching 1200rpm and over. Just sayin'.
And, I still don't see how you came to conclusion his idle was too high when he never mentioned how high it was reaching.
Last thing....another way to check for a bad IDL contact on the TPS: bend a paper clip over in half, insert either end in the diagnostic check box at Te1 and E1 terminals (port is the little grey or black box on the pass side wheel well. The lid flips over exposing terminals), and the idle should drop. If it doesn't, the IDL contact in the TPS is bad.
And, I still don't see how you came to conclusion his idle was too high when he never mentioned how high it was reaching.
Last thing....another way to check for a bad IDL contact on the TPS: bend a paper clip over in half, insert either end in the diagnostic check box at Te1 and E1 terminals (port is the little grey or black box on the pass side wheel well. The lid flips over exposing terminals), and the idle should drop. If it doesn't, the IDL contact in the TPS is bad.
07-08-2010, 05:16 AM
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I think the service manual says 1200rpm but I did not mean that as a set number. And when I say "high idle" I mean that the engine is getting more air then normal past the throttle plate while the TPS IDL contact is closed.
The idle circuit is just a switch. The ECU is not monitoring an analog signal for fuel correction when the switch is closed.
Yes it can be the TPS but in those cases the idle contact is most likely open. At that point the ECU is not in idle condition so the engine is reacting to TPS analog signal and AFM readings. That is why if you have a bad idle the first thing to check is the idle - E2 switch in the TPS. If this is closed then you have an air leak problem or AFM problem.
You also know that you can run the engine with no TPS at all. This is because the AFM runs these motors not the TPS. The Analog signal from the TPS is a correction factor for the fuel map but the fuel delivery increases on its own due to the AFM and RPM signals.
It is my understanding that the bouncing idle is the fuel being cut by the ECU. It sees that the idle contact is closed yet the RPM is to high (this rpm is 1100 - 1500 range, my experience). So it cuts the fuel. Then when the RPM drops back down it starts fuel again. Bounce bounce bounce
When the engine is not at normal temp it ignores the high RPM since the IAC valve must still be open.
This is just my understanding and how I fix idle problems on these trucks. There may be other conditions that cause this but almost every truck I look at with an idle problem comes back to TPS idle contact, low coolent (iac not closing), high idle (adjustment screw vacuum leak),dashpot.
The idle circuit is just a switch. The ECU is not monitoring an analog signal for fuel correction when the switch is closed.
Yes it can be the TPS but in those cases the idle contact is most likely open. At that point the ECU is not in idle condition so the engine is reacting to TPS analog signal and AFM readings. That is why if you have a bad idle the first thing to check is the idle - E2 switch in the TPS. If this is closed then you have an air leak problem or AFM problem.
You also know that you can run the engine with no TPS at all. This is because the AFM runs these motors not the TPS. The Analog signal from the TPS is a correction factor for the fuel map but the fuel delivery increases on its own due to the AFM and RPM signals.
It is my understanding that the bouncing idle is the fuel being cut by the ECU. It sees that the idle contact is closed yet the RPM is to high (this rpm is 1100 - 1500 range, my experience). So it cuts the fuel. Then when the RPM drops back down it starts fuel again. Bounce bounce bounce
When the engine is not at normal temp it ignores the high RPM since the IAC valve must still be open.
This is just my understanding and how I fix idle problems on these trucks. There may be other conditions that cause this but almost every truck I look at with an idle problem comes back to TPS idle contact, low coolent (iac not closing), high idle (adjustment screw vacuum leak),dashpot.
07-08-2010, 06:00 AM
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I would have to agree with thook in that, if you are getting the bad idle and pull the tps plug while it's running, it should even out the bounce.
Even if it's not the TPS, I replaced mine a few days ago in route to resolving an auto transmission problem and, the throttle response improvement alone was worth the $55 I spent for it. Is your throttle response very sluggish on acceleration/deceleration when you depress or lift off the gas peddle? Might be worth it for you anyway. It's a pain to pull: the idiot that decided on phillips head screws for the bolts was hopefully fired the first time someone tried to change theirs out, I had to take off the whole throttle body to get good access to the lower screw to cut it off once it stripped on my first attempt. The mechanism should return from spring tension with a crisp snap; mine would slowly return to position because of the years of accumulated deposits. It was a "no brainer" improvement for me.
Even if it's not the TPS, I replaced mine a few days ago in route to resolving an auto transmission problem and, the throttle response improvement alone was worth the $55 I spent for it. Is your throttle response very sluggish on acceleration/deceleration when you depress or lift off the gas peddle? Might be worth it for you anyway. It's a pain to pull: the idiot that decided on phillips head screws for the bolts was hopefully fired the first time someone tried to change theirs out, I had to take off the whole throttle body to get good access to the lower screw to cut it off once it stripped on my first attempt. The mechanism should return from spring tension with a crisp snap; mine would slowly return to position because of the years of accumulated deposits. It was a "no brainer" improvement for me.
07-08-2010, 12:59 PM
#17
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I think the service manual says 1200rpm but I did not mean that as a set number. And when I say "high idle" I mean that the engine is getting more air then normal past the throttle plate while the TPS IDL contact is closed.
The idle circuit is just a switch. The ECU is not monitoring an analog signal for fuel correction when the switch is closed.
Yes it can be the TPS but in those cases the idle contact is most likely open. At that point the ECU is not in idle condition so the engine is reacting to TPS analog signal and AFM readings. That is why if you have a bad idle the first thing to check is the idle - E2 switch in the TPS. If this is closed then you have an air leak problem or AFM problem.
You also know that you can run the engine with no TPS at all. This is because the AFM runs these motors not the TPS. The Analog signal from the TPS is a correction factor for the fuel map but the fuel delivery increases on its own due to the AFM and RPM signals.
It is my understanding that the bouncing idle is the fuel being cut by the ECU. It sees that the idle contact is closed yet the RPM is to high (this rpm is 1100 - 1500 range, my experience). So it cuts the fuel. Then when the RPM drops back down it starts fuel again. Bounce bounce bounce
When the engine is not at normal temp it ignores the high RPM since the IAC valve must still be open.
This is just my understanding and how I fix idle problems on these trucks. There may be other conditions that cause this but almost every truck I look at with an idle problem comes back to TPS idle contact, low coolent (iac not closing), high idle (adjustment screw vacuum leak),dashpot.
The idle circuit is just a switch. The ECU is not monitoring an analog signal for fuel correction when the switch is closed.
Yes it can be the TPS but in those cases the idle contact is most likely open. At that point the ECU is not in idle condition so the engine is reacting to TPS analog signal and AFM readings. That is why if you have a bad idle the first thing to check is the idle - E2 switch in the TPS. If this is closed then you have an air leak problem or AFM problem.
You also know that you can run the engine with no TPS at all. This is because the AFM runs these motors not the TPS. The Analog signal from the TPS is a correction factor for the fuel map but the fuel delivery increases on its own due to the AFM and RPM signals.
It is my understanding that the bouncing idle is the fuel being cut by the ECU. It sees that the idle contact is closed yet the RPM is to high (this rpm is 1100 - 1500 range, my experience). So it cuts the fuel. Then when the RPM drops back down it starts fuel again. Bounce bounce bounce
When the engine is not at normal temp it ignores the high RPM since the IAC valve must still be open.
This is just my understanding and how I fix idle problems on these trucks. There may be other conditions that cause this but almost every truck I look at with an idle problem comes back to TPS idle contact, low coolent (iac not closing), high idle (adjustment screw vacuum leak),dashpot.
Anyway.....
I see what your calling a "bouncing" or "hunting" idle. And, I had a feeling your explanation would be the technicality I was asking for elaboration on. Thanks....really.
I am aware of those functional parameters, but I guess I find it difficult to make a definite diagnosis without getting more detail about the symptom. '88red isn't terribly descriptive about the problem.
You describe situations where the IDL is either open or closed. I see an intermittent IDL to ground being able to create the same or similar circumstance without the RPM necessarilly going high enough to trigger fuel cut. Since the ECU is quick to respond (under "healthy" conditions) to voltage feedback, once the IDL signal is broken, the timing adjustment is no longer present. Then, once the signal is restored, timing adjustment resumes.....up and down. But, from what you're describing as a "bounce", the symtom in this case wouldn't necessary behave in the same manner as a steady up and down as with fuel cut. More of an unsteady fluctuation......as if someone were lazily resting their foot on the accelerator. A little detail, I suppose the '88red would care to elaborate on? Nevertheless, given what we have to go on from '88red, I believe you're probably right.....though, you also said it could be the TPS.
Doesn't hurt to check it. Simple enough.....
07-08-2010, 01:20 PM
#18
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You're welcome, Fink. I'm not, and never have been, here to create waves.....even though I may done so. Flash has always had good info and I've learned from reading his posts. That's all I'm really interested in.
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