BandY Posted February 13, 2015 Report Share Posted February 13, 2015 Came to work at ten this morning, and only had to do things until about two. So, since that was the warmest part of this chill weather, I decided to try to explore my bad running problem. Anyhow, long story short, I wanna know opinions on whether I can drive it without any TPS on it. I mean, I have the TPS off, and unplugged. I remember that years ago, on a different '86, I ran the car for about three or more years with the TPS unplugged, and it seemed to do fine. Unplugging it kept it from searching for an idle speed. Looking for some thoughts on this. I can get a ride home, but I'd RATHER NOT LEAVE THE CAR HERE AT NIGHT. Thoughts???? Thanks. Link to comment Share on other sites More sharing options...
Skullzaflare Posted February 14, 2015 Report Share Posted February 14, 2015 i know on 87+ it pretty much cuts the car off after idle, never owned a 86 Link to comment Share on other sites More sharing options...
importwarrior Posted February 14, 2015 Report Share Posted February 14, 2015 I thought 86 can run with the MAF unplugged. Not TPS Link to comment Share on other sites More sharing options...
freebird Posted February 14, 2015 Report Share Posted February 14, 2015 i didnt think any car could run without the tps??? Maybe a 80's carb engine. Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 (edited) I'm aware of that. This '86 seems to be the same way. My other '86 didn't need it. Odd, since they were both built in May of 1986. Not sure about the MAF or MAS being unplugged, but it would run without the TPS. I had never messed with the MAF, since I had no problems, that I know of. haha Edited February 14, 2015 by BandY Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 I checked it one more time, and something seems out of whack. Like I've posted in Virtual Mechanic, the TPS is reading backwards. I did notice, though, that there is a picture of another car in the gallery, and its TPS wires are facing upwards, like mine are. Still, if I turn the TPS completely clockwise, I get 5.00 volts. The only way to get .48 or .50 volts is if I pull the accelerator cable out a few inches. Link to comment Share on other sites More sharing options...
Shelby Posted February 14, 2015 Report Share Posted February 14, 2015 it is the air mass that some 86's will run with out , not tps Link to comment Share on other sites More sharing options...
Shelby Posted February 14, 2015 Report Share Posted February 14, 2015 (edited) if the wires are mixed up going to a tps it will read back wards , fact is most will read eather way depending on how the power wire is ran Edited February 14, 2015 by Shelby Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 (edited) It would be an amazing discovery, if I was to verify that the wires are backwards. Obviously, I will make sure, before cutting anything. Been waiting for you to chime in, Shelby. Your opinion is always very valuable to me. Edited February 14, 2015 by BandY Link to comment Share on other sites More sharing options...
mikec Posted February 14, 2015 Report Share Posted February 14, 2015 The TPS is used by the ECU to mimic a carburetor accelerator pump and fuel cut function - i.e. it senses CHANGES in throttle position mostly. If the TPS output voltage is increasing, the ECU knows "driver wants to accelerate - dump in more fuel to help get the engine RPMs up." When the TPS voltage drops a bit, the ECU interprets that as "driver just lifted off the throttle pedal... don't need any gas to decelerate!" Most StarQuests without a working TPS will be hard to drive unless you accelerate slowly. 86 models use a totally different algorithm to compute fuel compared to other model years cars... so they may respond differently to a missing TPS. Most model years won't be at all driveable (most won't even start) if the airflow sensor (normally the primary input to the ECU) is bad for example... but some 86s run reasonably well with the airflow sensor disconnected. Those 86s probably won't run for crap without the TPS. You won't damage the engine driving any model year StarQuest with a disconnected TPS. Just be careful and avoid areas with traffic as you won't be able to accelerate with traffic. Shifting will take some extra concentration too. mike c. Link to comment Share on other sites More sharing options...
Shelby Posted February 14, 2015 Report Share Posted February 14, 2015 (edited) the following applys only to 87 up cars ,sorry i didn't think we were talking about an 86 the quest ecu uses the tps to turn on both injs during WOT , so with low tps voltage signal the sec inj may work but the pri inj will not turn back on during WOT , so you will see a drop in performance in the higher rpms range like Mike said the ecu see's the voltage change , and many after market ecus will learn the voltage change eather higher or lower , but our old ecu can't lean this voltage swap as it's a little too primitive Edited February 14, 2015 by Shelby Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 Well, keep in mind, it's an '86, so there is no primary or secondary. I left the car here last night, and now that I'm back, I see that nobody messed with it. RELIEVED. Hooked my meter to the TPS once again, and verified that it reads backwards. Car not running, it reads 5 volts. Then, if I slowly open the throttle to wide open, the volts slowly drop all the way down to zero. If I reverse the meter wires on the plug, it reads negative 5 volts, and then goes to zero at wide open. What's got me really surprised is that both TPSs I have do the exact same thing. Makes me think that wiring in the car itself could be reversed somewhere. Is that possible???? I'm hesitant to reverse the striped wires on the TPS, but I will, if that will solve my problems. For all I know, reversing the wires might not even have the effect I'm hoping for. Link to comment Share on other sites More sharing options...
StarquestRescue Posted February 14, 2015 Report Share Posted February 14, 2015 I checked it one more time, and something seems out of whack. Like I've posted in Virtual Mechanic, the TPS is reading backwards. I did notice, though, that there is a picture of another car in the gallery, and its TPS wires are facing upwards, like mine are. Still, if I turn the TPS completely clockwise, I get 5.00 volts. The only way to get .48 or .50 volts is if I pull the accelerator cable out a few inches.Pull the tps off and reinstall with the wires down. I think the signal will move the correct way then. Link to comment Share on other sites More sharing options...
Shelby Posted February 14, 2015 Report Share Posted February 14, 2015 5 volt reference feed and signal out ,,keep the -ground where it is ,and you are right my coment was referring to the pri -sec set up 87 up Link to comment Share on other sites More sharing options...
StarquestRescue Posted February 14, 2015 Report Share Posted February 14, 2015 It is the 5 volt and ground wire that needs to be reversed. Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 They won't line up with one another, upside down like that. I wish they would. Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 So, these are the wires now. Green with a black stripe, is the one by itself. The other two are green/red stripe, and green/white stripe. Which ones should I switch? Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 The two that are closer together are the ones I was having the meter on. I'm pretty sure that going to the lone wire with either of the other two would give me no reading. Either that, or 5 volts, regardless of throttle position. Link to comment Share on other sites More sharing options...
StarquestRescue Posted February 14, 2015 Report Share Posted February 14, 2015 Test each wire to the battery negative . One will be ground with no voltage, one will change when the throttle is opened. One will be 5 volts all the time. Switch the constant 5v and the ground. Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 Thank you for that. I'll get right on it now... Link to comment Share on other sites More sharing options...
StarquestRescue Posted February 14, 2015 Report Share Posted February 14, 2015 The 85 manual says Black is groundGreen white is signalGreen red is 5 volt. Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 Before I go any further, here's an update that might be giving a different message. Possibly that might be screwing up by reversing anything. So, using the negative terminal on the battery as where I connect the negative from the meter, these are the readings I get... The green/red reads .79 to 5.00 at wide open throttle. The green/white reads constant 5.00 volts. The green/black reads constant .03 volts. I assume this is the ground. Should I change anything, or are these proper readings? It seems so odd that using the battery ground has me a lot closer to getting the readings I need, even though .79 is not low enough. Link to comment Share on other sites More sharing options...
BandY Posted February 14, 2015 Author Report Share Posted February 14, 2015 According to that 85 manual, then, those two are reversed? Link to comment Share on other sites More sharing options...
Shelby Posted February 14, 2015 Report Share Posted February 14, 2015 Test each wire to the battery negative . One will be ground with no voltage, one will change when the throttle is opened. One will be 5 volts all the time. Switch the constant 5v and the ground. thanks StarquestRescue it's been a while sence I had to change the wireing on one Link to comment Share on other sites More sharing options...
StarquestRescue Posted February 14, 2015 Report Share Posted February 14, 2015 Check the harness side to battery ground again with the tps disconnected. The manual says the green red should be the 5 volt. If the signal wire do not match up on both sides of the plug strange things will happen. Link to comment Share on other sites More sharing options...
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