Which is better (or worse): no tps or a bad tps?

Posted by Spoolin4Ever, Aug 18, 2005
Newbie Forum - Beginner DSM modification questions and discussions. Common, repetitive, and general discussions will get dumped here from other tech forums. Unless you're a Probationary member you shouldn't post threads here.

  1. Spoolin4Ever

    Spoolin4Ever Proven Member

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    I've got a TPS that needs replaced, but I don't have the money for the part right now.

    I unplugged it, and the car runs much better with it unplugged then with it plugged in.

    Is it bad for the car to drive it with the TPS unplugged?

    What are the ramifications? Effect fuel mileage?

    Can it cause any damage?

    If you had to choose between driving with a bad TPS or just unpluggint it, which would you do?

    1G AWD/Manual :dsm:
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  2. TurboDSM86

    TurboDSM86 Proven Member

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    Running with out it will set to a base program. I would unplug it but drive it NICELY and as least as possible until you can fix it. A bad one can cause you a world of problems while driving (im sure youve noticed LOL. Your mileage may actually go up over driving with the bad one. Dont expect killer mileage though. Replace it soon :thumb:
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  3. Spoolin4Ever

    Spoolin4Ever Proven Member

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    Thanks for the response.

    In regarding to driving with it unplugged?

    Does it hurt anything though? I mean like does it cause any detonation or anything really bad.
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  4. TurboDSM86

    TurboDSM86 Proven Member

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    Dont beat on it and you will be ok.
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  5. xveganxcowboyx

    xveganxcowboyx Proven Member

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    Buy one used from somebody. I just replaced mine for $10 or $15. Easy and much better than $150 from the dealer/parts store.

    As for driving with it on, I can attest to the problems it causes (or MAY cause, they won't all act the same). I got about 12mpg while babying the gas and only ran well at WOT. No matter what I did my turbo and manifold were always RED hot after driving any distance. Obviously the thing was sticking at full fuel and dumping more than I needed.

    Another possible negative side effect. By dumping that much fuel and getting that hot it's not too hard to cook your cat.
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  6. Spoolin4Ever

    Spoolin4Ever Proven Member

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    I had already purchased a used one, but was unsure if it's good. I went to the tps test pages, and was a little confused. Because one page is for when it's on the car, the other is with it off the car, but I think it's a 2G, cause it looks like it has the ISC or something conncted to it, as it has 2 screws in it even though it's off the car. It made me wonder if i have to look for different results, cause mine when off the car is just the plastic black TPS, the screws are not in it, there is nothing else attached.

    Here are my test results:
    It should read 5K Ohms. This is the resistance in the closed throttle position.
    Mine was >>>>>>>>>>>>>4.27.

    With the throttle closed it should read .9K Ohms (Changed per Data logger). Pic shows 1.1K Ohms
    Mine is .15, but it doesn't apply i guess, cause it's not attached?

    Open the throttle all the way open and the meter needle should move while opening and stop at 5K Ohms.
    Mine was >>>>>>>>>>>>4.44

    Mine does go up gradully when you turn it (the ohms)

    Is this from a 2G?
    http://www.plymouthlaser.com/tps.htm

    I wonder what the correct way to TEST it on a 1G off the car?
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  7. steve

    steve DSM Wiseman

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    Nope, it's 1G specific and you need to ignore the part about adjusting via resistance unless you measure your +5v sensor voltage at the TPS, the TPS's total resistance and do the math to find the correct value to give the requires voltage output.

    So what's needed to test a 1G 4G63 TPS?

    First the specifications from the FSM are:

    Total resistance (between 1 and 4) 3.5k to 6.5k Ohms

    Resistance between pin 2 and 1 needs to increase ( or decrease between 2 and 4) smoothly as you rotate the shaft. No jumps, spikes, or dropouts and it needs to continue doing so when hot.

    Once it's on the car the TPS needs to be adjusted at idle with the throttle closed to read 0.48v to 0.52v with 0.5v being nominal. That equals a reading of 10% on a datalogger.

    That's it.

    Note: I've said nothing about what it reads at WOT at all. Because what it reads at WOT doesn't matter as long as the throttle plate opens all the way and the output of the TPS is smooth and consistant.

    Steve
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  8. Spoolin4Ever

    Spoolin4Ever Proven Member

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    OK,

    Well I think I want to go ahead and try switching out the part with this used one I bought online.

    What is the easiest way to do it?

    Do I have to take the TB off?

    Thanks...:)
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  9. steve

    steve DSM Wiseman

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    Take the throttle body off. It's next to impossible to get at the lower bolt on the TPS on the car unless you want to the the fuel rail off.

    Steve
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  10. Spoolin4Ever

    Spoolin4Ever Proven Member

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    "Once it's on the car the TPS needs to be adjusted at idle with the throttle closed to read 0.48v to 0.52v with 0.5v being nominal. That equals a reading of 10% on a datalogger."

    Well how do you adjust it on the car, it's a total PINA to adjust it on the car cause the screw location?

    I have the TB off the car and have switched out the parts. I adjusted it it says .90, closed position off the car. I had to turn it most all the way to achieve that .90 at closed throttle. Is this what I am supposed to do? It says so at the plymouth laser site.

    Can I just slap it on now and it will work?

    By the way, in comparing the 2 different parts, it looks like my replacement part does change smoother when you rotate it, I mean the old one jumps pretty high in comparison, sometimes in the 10's in just a little bit of movement. Based on that comparison, I may have gotten a good part. That's what my hopes are.
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  11. steve

    steve DSM Wiseman

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    There are several ways. You can make up a service connector like shown in the FSM to measure the voltage at the TPS. You can connect a voltmeter to pins 19 and 24 on the ECU. You can look at the sensor voltages on a SAFC (if you have one) or you can attach a datalogger (if you have one or can borrow one) and adjust for 10% which is 0.5v out of a possible 5v.

    I set the bottom bolt just tight enough that it's hard to turn the TPS and then lock the TPS with the top bolt, which you can reach on the car.

    I've already said why that procedure is wrong. I'm getting tired of correcting the error, so I guess it's time to fire off an email to Charles and ask him to fix the VFAQ.

    Steve
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  12. Spoolin4Ever

    Spoolin4Ever Proven Member

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    OK

    I will set it on the car like you said.

    I think your idea of correcting the information that's out there is a good idea. And frankly, I am suprised at how little information there is out there on the TPS.

    Looks like an opportunity for ya there ;)
    #12
  13. Spoolin4Ever

    Spoolin4Ever Proven Member

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    I got the part on the car, but I think I misunderstood which screw to tighten and which one to leave. I tightened the bottom one alot, and left the top one looser.

    My TPS reads .88 V at idle, which is 17% open at idle. Driving like this, is that running rich or lean? I would think rich cause the ECU will think I have the gas mashed more then I really do.

    WOT says 100%

    I got to open her back up again, and make it so I can adjust it, the bottom screw is too tight.

    By the way, mine is turned so that all most all the adjustment is used up. If you were to adjust it down, clockwise rotation, there is practically zero room to move it. The other way, counterclockwise there is plenty of room naturally.

    Which way do I need to turn it to lower the voltage? Hopefully counterclockwise. I will check the FAQ's again for this also.

    Thanks again.
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  14. steve

    steve DSM Wiseman

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    Except during limp mode with a bad MAF the ECU isn't really looking at the value of the TPS so much as it's looking at the changes in value to tell it what to do. The fuel calculations are based off the airflow readings from the MAF with corrections for acceleration, deceleration, open or closed loop, and what not.

    There is more going on with the TPS on a ATX car where the TCU uses it for deciding when to shift.

    You should get your hands on the 1G DSM tech manual. There is lots of good information in it.

    Steve
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  15. Spoolin4Ever

    Spoolin4Ever Proven Member

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    In regard to the shop manual; I have the CD version, I just get frustrated in the search capabilities and often have a hard time finding what I need to know.

    The car is running pretty fast compared to either of the 2 scenarios over about the past year:

    1. Running with a bad TPS throwing codes (poor performance, mileage wasn't real bad, about 18-23 depending). The bucking and studdering are troublesome and the pickup is slow, the timing was getting retarded.

    2. Running with the TPS unplugged: Mine ran better this way then with the bad tps. Mileage went down a little actually. But it was faster miles ;)

    So now it just runs a little faster then number 2, I have only driven it to the store and back. I was kinda easy on it, I got into it a little bit. Runs almost like a new car compared to before. I was suprised how much of a difference it made.

    So it sounds as if I can drive it like this, but if it goes into limp mode, will it just make my limp mode a little more limpier then your basic limp mode? :coy:

    Should I be concerned?


    I was thinking of trying it again anyway; the weekend is here so it's cool. Plus I have already got into it this much. Now at least I'm comfortable doing it.

    Well hopefully I won't break a coolant hose this time ;) A shorter screwdriver for working with the hose clamps would help too, kinda tight in there.

    This job reminds me of the starter job. About the same in difficulty, and kind of in the same area. Not too hard, but not quite as EZ as plugs hehe.
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  16. Spoolin4Ever

    Spoolin4Ever Proven Member

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    One problem: When the car is cold there is a dip in the throttle reponse at first. It wasn't there before, so I think it's because the TPS is set at .88 voltage/17% throttle at idle. A slight hesitation each time you give it throttle, just at first, then picks back up.

    Once it warms up to temp, it drives really good/fast/normal.
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  17. steve

    steve DSM Wiseman

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    If you have the manual CD and not some other disk. Go to the 1G DSM Technical manual and read the part under Fuel System on the TPS. The rest of the Fuel System section is also very interesting.

    Steve
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  18. Spoolin4Ever

    Spoolin4Ever Proven Member

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    OK I adjusted it to about .50, the car now seems to run better still. The little dip in throttle response in the low end looks like it went away. I only drove it around the block.

    So if it changes I will report back.

    Looks as if Steve is correct, the TPS FAQ is wrong, set it to about .50 at idle on the car. Setting at .90 makes it cut out when you first apply the throttle, especially when the car is cold.
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