88XJSport Posted April 11, 2009 Share Posted April 11, 2009 Ive been chasing my tail with a intermittent low/rough idle, trying to think back to when it started, and I remembered adjusting my TPS for the first time a few months back, and it may or may not have controbuted to my low/rough idle. So, would adjusting a TPS from 80% to the reqired 83% make my idle low and rough? Link to comment Share on other sites More sharing options...
BLHTAZ Posted April 11, 2009 Share Posted April 11, 2009 Here is the proper way, per the FSM, to check and adjust a TPS... viewtopic.php?f=9&t=12260 I don't know where ya'll are getting this percentage thing, but it is not the way to do it. You are the second person to post about the percentage adjustment today, and I have never heard of that before today. :dunno: Try the correct testing and adjusting, then report back. The TPS does not typically cause a rough idle problem though. Link to comment Share on other sites More sharing options...
Ed in North Ga. Posted April 11, 2009 Share Posted April 11, 2009 Here is the proper way, per the FSM, to check and adjust a TPS... viewtopic.php?f=9&t=12260 I don't know where ya'll are getting this percentage thing, but it is not the way to do it. You are the second person to post about the percentage adjustment today, and I have never heard of that before today. :dunno: Try the correct testing and adjusting, then report back. The TPS does not typically cause a rough idle problem though. the "percentage" is from Chiltons manuals- and some haynes. It is a descriptor- merely a way of explaining it and not its actual basis. I`d have to pull the original chilton manual to explain it better- its like the "final result" of the equation, when the answer isnt explained as what it is (example .10) as what it could be (example 10%)- half inch vacuum, 50% of an inch, .50- beer need more beer. Link to comment Share on other sites More sharing options...
88XJSport Posted April 11, 2009 Author Share Posted April 11, 2009 Yes I adjusted it per Chiltons, but the FSM seems similar. My input voltage was 4.66, and I adjusted my output voltage to 3.87, to get 0.830. Before I adjusted, my output voltage was 3.0. And since 3.0/4.66 is 0.815, and the output should be ~.83, I adjusted the output voltage to 3.87, from the original 3.0. Like I said, I'm not sure if that causes my rough idle, but it was worth looking into. Link to comment Share on other sites More sharing options...
BLHTAZ Posted April 12, 2009 Share Posted April 12, 2009 AHHHH... :idea: Chiltons/Haynes - They will lead you down the wrong path 80% of the time :ack: :shake: . They have some good info in them...BUT..very little. This is obviously one of those times when they are useless. Link to comment Share on other sites More sharing options...
rworks Posted April 12, 2009 Share Posted April 12, 2009 When I adjusted mine, I looked at the FSM instructions and figured that 5.0 - 4.2 = 0.8 Given that my input voltage was 4.65 volts, I simply subtracted 0.8 and set the TPS to 3.85 volts. Worked fine. Idles great. Link to comment Share on other sites More sharing options...
Ed in North Ga. Posted April 12, 2009 Share Posted April 12, 2009 see, the odd part of all this, is the TPS has very little effect on base idle- it sets it up, but the IAC controls it (renix)- anytime the idle is/was off on either of mine- throttle body clean, IAC clean, bore for IAC clean- THEN reset the TPS, and a quick search for a vac leak- it solved my idle problems every time, without fail. It never was anything else. In my opinion, its ALWAYs related to one of the above, and instead of searching for the single problem, I shotgun`d it. Ive yet to run into one of the high / low idle problems, the 2500/3000 high idle start up- but when I do, I`ll learn that fix. Link to comment Share on other sites More sharing options...
dakal Posted April 13, 2009 Share Posted April 13, 2009 according to alldata 5.0v and .8 v the percentage difference is 16%. since my mechanic and i couldn't get the 5.0v and .8v, we took what we could get. i think it was 4.87 or 4.78v. then we did 16% of that for our output v and it is fine. :yes: Link to comment Share on other sites More sharing options...
BLHTAZ Posted April 13, 2009 Share Posted April 13, 2009 I think everyone is missing the point. No matter what the input voltage, 5.0, 4.8 or 5.2, the output should be .8v. The percentage stuff needs to be forgotten as it is not right. Mine has an input of 4.8v, but when adjusted to the proper output of .8v, it runs the best. .8v is 16% of 5.0v. - The voltage "difference" in that equation is 80% ;) Link to comment Share on other sites More sharing options...
88XJSport Posted April 13, 2009 Author Share Posted April 13, 2009 I think everyone is missing the point. No matter what the input voltage, 5.0, 4.8 or 5.2, the output should be .8v. The percentage stuff needs to be forgotten as it is not right. Mine has an input of 4.8v, but when adjusted to the proper output of .8v, it runs the best. .8v is 16% of 5.0v. - The voltage "difference" in that equation is 80% ;) That makes a lot of sense. Since my input voltage was 4.66, and since it doesnt matter, I adjusted my output voltage from .8v to .83. I should move it back to the way it was to see if I notice a difference. Link to comment Share on other sites More sharing options...
dakal Posted April 13, 2009 Share Posted April 13, 2009 gotya when my jeep is back together again i will adjust output to .8v to see if it runs better than it was. its close to that now, but i don't remember what the value is. Link to comment Share on other sites More sharing options...
BLHTAZ Posted April 13, 2009 Share Posted April 13, 2009 Please don't get me wrong...it's not that the input "doesn't matter", as it should be as close to 5.0v as possible, but it's not going to be perfect on any of them. The output is what you are adjusting to keep it at .8v. If the input is significantly off from 5.0v, then you should be looking in to that as well. The small variances on input posted here so far should not make a difference. :cheers: Link to comment Share on other sites More sharing options...
dakal Posted April 13, 2009 Share Posted April 13, 2009 :cheers: Link to comment Share on other sites More sharing options...
rworks Posted April 13, 2009 Share Posted April 13, 2009 I think everyone is missing the point. No matter what the input voltage, 5.0, 4.8 or 5.2, the output should be .8v. The percentage stuff needs to be forgotten as it is not right. Mine has an input of 4.8v, but when adjusted to the proper output of .8v, it runs the best. .8v is 16% of 5.0v. - The voltage "difference" in that equation is 80% ;) Exactly. My input voltage was 4.65, so subtracted 0.8 and got a reading of 3.85v. No % nonsense needed. Link to comment Share on other sites More sharing options...
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