techboy Posted February 21, 2011 Report Share Posted February 21, 2011 Yesterday I swapped my new rebuilt TB onto my car. After the install I walked through the reset procedure for the first time. I printed out both methods listed in the FAQ and walked through them both (I tried each method) meticulously. I was able to attain a MPS voltage of .9 at an idle speed of 850I believe the throttle cable is at the proper tension.With the ISC plugged back in the car's curb idle is about a grand. The best I can get on the TPS is .38V all the way clockwise. With it all the way CCW I get a reading of .10V. I swapped in another TPS off my old TB and got the same thing. Now, the kicker is the car runs 5X's better than before .... so how critical is it that achieve the .50V? Any thoughts/feedback? Just in case, I'll also mention, although I don't think this influences the readings I'm getting on the TPS, that the car seems to be running a bit rich. It stumbles over itself a little bit at idle and if you introduce a vacuum leak it smooths right out. So, it doesn't seem to be getting enough air in the mixture. I'm going to replace the plugs and wires b/c I don't know when they were last done by previous owners and I'm wondering if there's not enough spark to burn up all the fuel and see if that fixes it. But, I'm still perplexed by the whole TPS thing. Link to comment Share on other sites More sharing options...
Indiana Posted February 21, 2011 Report Share Posted February 21, 2011 I believe the throttle cable is at the proper tension. The best I can get on the TPS is .38V all the way clockwise. how critical is it that achieve the .50V? Any thoughts/feedback? I'm wondering if there's not enough spark to burn up all the fuel and see if that fixes it. The cable isn't to have any tension at idle, its to be loose so that the tip switch will always close. Leave the TPS unplugged, What voltage do you get from the harness? You need to see at least .48v or a bit higher. The sensor power wire from the ECU is from pin10 a green wire w/red stripe (ground is the green w/black stripe don't use a body ground only the ECU ground). Maybe both TPS you have are bad, or something else in the sensor power circuit is causing that or there's a bad connection or your ECU is bad. The TPS doesn't ever need to see five volts, only 4.5v and this changes the ECU so that it dumps more fuel and ignores the 02. You would have to unplug the MPS while you check that also the MAF shares this wire unplug it too and see what max voltage you see from that green w/red stripe wire. If you have the proper voltage at the harness and plugging in the MAF didn't effect that, then both your TPS would appear to be bad. Only being able to drop down as low as .1v for the TPS won't let the idle motor do anything to control idle after the coolant is hot but its low enough for the cold idle range and would explain why the idle motor didn't drop rpms when you plugged it in and raised it then stopped if the motor was still cold. Was the motor hot when you did this or still cold? A plug that sparks will burn fuel but maybe not completely if the plug is fouled or the wrong type of plug but its timing that gives the fuel enough time to burn. The plug is there to remove heat from the combustion process. Which plug part# do you have? Link to comment Share on other sites More sharing options...
Shelby Posted February 21, 2011 Report Share Posted February 21, 2011 i'd guess the ecu is in open loop http://www.starquestclub.com/forum/public/style_emoticons/default/unsure.gif and what yr is this car , i know the pre 87's said to turn tps all the way but , that realy don't sound right, very few ecu systems use a tps voltage that low, nearly every thing uses a base tps reading of aprox .500 volts the exact voltage is not as important as the fact that it changes from low to high Link to comment Share on other sites More sharing options...
techboy Posted February 21, 2011 Author Report Share Posted February 21, 2011 (edited) Indiana - the engine was warmed up when I performed the reset. After installing the TB I let the car idle until I had pressure in the rad hose and the fans kicked on. I'd say it ran for at least a good 6-8 minutes. Then I started working my way through the procedure. Next time I have a chance to work on it I will check the voltage at the sensor power wire as you described. Unfortunately it's snowing today. I don't know what plugs are in the car, I haven't removed them yet. I would like to pick up new ones this week and replace, whatever the manufacturer calls for, I tend to prefer NGK's for my cars. Shelby - The car is an 88. I was reading through some other TPS reset posts here on the board while doing some research and I found some guys who said I might to do this a few times after driving the car a bit. Maybe I'll drive it a few times this week and try the process again. Edited February 21, 2011 by techboy Link to comment Share on other sites More sharing options...
DzNutz Posted February 22, 2011 Report Share Posted February 22, 2011 Engine needs to be at operating temp and in between some of the settings you need to rev the motor and let it idle for a bit for the ECU to find its arse again. The TPS voltage almost sounds like the internal is not lined up properly. What voltages do you get on a throttle sweep? Link to comment Share on other sites More sharing options...
Chad Posted February 22, 2011 Report Share Posted February 22, 2011 sounds silly, but make sure the TPS arm is propperly connected to the rotating gear on the throttle shaft. Voltage is supposed to track with throttle posisition, ~0.5 volts is idle, and ~4.5 volts is wide open, and a nice linear voltage increase with throttle change between the two. If voltage isn't tracking correclty with the throttle changes, it may not be correclty connected to the shaft inside. Double checking yoru connections; you shoudl find one that is +5 volts, one that is a ground, and one that changes with throttle. If you use the wrong ground refrence, you can get incorrect readings despite correct opperation. It's best to use the battery, block, or chassis as your ground and find the lead that changes voltage with throttle for your measurements. Link to comment Share on other sites More sharing options...
Shelby Posted February 22, 2011 Report Share Posted February 22, 2011 when doing these rest procedures always test all 3 wires for proper read out one will show a groundone will show almost 5 voltsand one will be a signal voltage you can not get the system to work if any one of these wires are not properly reading , this applys to the TPS, MPS the ISC uses a posi neg reversing from the ecu so as long as the motor runs it's ok the CTS recives a 5 volt signal and the other wire goes to an ecu internal ground ,,but that ground may not be there unless the engine is runing ,,seems the diff year ecus do this a little diff from one yr to another Link to comment Share on other sites More sharing options...
techboy Posted July 14, 2011 Author Report Share Posted July 14, 2011 (edited) I'm following up on this thread from February .... I'm still only seeing .36 - .38V at my TPS and I'm 100% convinced at this point this is the problem w/ the stumbling, rough idle, and stalling at low RPM's. I went out and bought an analog voltmeter yesterday and bench tested both the TPS's I own as per Professor Quests directions on starquest forums. They both sweep very nicely, w/ no hesitation. As far as I can tell they both seem to be operational. I get the same readings w/ either TPS installed. Oh, and the TPS signal wire reads 4.95V w/ the key forward. Shelby mentioned before in another thread that the car sounds like it's stuck in open loop ... which I agree with. How long does the car stay in open loop before it's "warmed up" enough to go to closed loop? Are we talking 1-2 minutes or more like 10-15? Do you think my ECU is bad or a bad connection somewhere? Indiana mentioned that in his first response. I'm getting tired of trying to figure this car out. :mad: Edited July 14, 2011 by techboy Link to comment Share on other sites More sharing options...
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