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  • annoying high idle issues

    My 91 coupe has all of a sudden started having high idle issues, and I don't know what the dam problem is. I have removed the throttle body, iac, egr, mass air and cleaned them. I have also cleaned the connections on all of them to, including the main connectors behind the intake. I can't find any vacumen issues either, that I am aware of. Also my set screw is all the way out, and the tp sensor has been replaced. Now what? My car starts and idles normal for about a minute, then jumps up to around 1200 rpms and won't come back down. Please help me guys, this shit is annoying.


    Originally posted by That_Is_My_El_Camino
    I grinned, but I have a sneaky suspicion I'm still gay.

  • #2
    I didn't see a thread on this, so sorry if this is a repost.


    Originally posted by That_Is_My_El_Camino
    I grinned, but I have a sneaky suspicion I'm still gay.

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    • #3
      It's, "vacuum," dude.
      ZOMBIE REAGAN FOR PRESIDENT 2016!!! heh

      Comment


      • #4
        When you did the tps did you reset the idle and check the TPS voltage at idle? Was the IACV really dirty? Have you ever checked the timing?

        I had a funky high idle on my coupe this time last year, I had to clean the throttle plate, IACV and reset the idle with the TPS.

        320rwhp. 7.67 @ 90mph 1.7 60'

        DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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        • #5
          The timing has been the same since I got the car, the iac really wasn't dirty, but I cleaned it anyways. The egr was freaking nasty, but it didn't make a difference after cleaning that either. As for the tp sensor, it has been replaced, and at the factory location. I did drill out the holes on one to see if I could get any kind of difference with adjustment, but no luck. I will check for vacuum leaks again tomorrow.


          Originally posted by That_Is_My_El_Camino
          I grinned, but I have a sneaky suspicion I'm still gay.

          Comment


          • #6
            Originally posted by Yale View Post
            It's, "vacuum," dude.
            Yeah that's what I get, when I'm using my stupid phone.


            Originally posted by That_Is_My_El_Camino
            I grinned, but I have a sneaky suspicion I'm still gay.

            Comment


            • #7
              Originally posted by fordplay2 View Post
              The timing has been the same since I got the car, the iac really wasn't dirty, but I cleaned it anyways. The egr was freaking nasty, but it didn't make a difference after cleaning that either. As for the tp sensor, it has been replaced, and at the factory location. I did drill out the holes on one to see if I could get any kind of difference with adjustment, but no luck. I will check for vacuum leaks again tomorrow.
              Being installed in the factory location is irrelevant, you have to check the voltage to set it correctly. ~1v idle and ~5v WOT. To me it sounds like the TPS and IACV could be the cause. A lot of the time the IACV pin with get carbon build up and cause it not to close properly.

              320rwhp. 7.67 @ 90mph 1.7 60'

              DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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              • #8
                If you take the TPS off and twist the sensor with the car running, you can see how it can effect the idle rpm.

                If the IACV is sticking sometimes a tap from a hammer will free it.

                320rwhp. 7.67 @ 90mph 1.7 60'

                DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

                Comment


                • #9
                  Originally posted by 91CoupeMike View Post
                  Being installed in the factory location is irrelevant, you have to check the voltage to set it correctly. ~1v idle and ~5v WOT. To me it sounds like the TPS and IACV could be the cause. A lot of the time the IACV pin with get carbon build up and cause it not to close properly.

                  And a lot of times voltages don't mean jack either. This plays a HUGE factor on the GM TPI engines. Couldn't get the idle down on my mom's 89 IROC, finally just let it run while adjusting the TPS, once it settled, it was A OK.

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                  • #10
                    Originally posted by JC316 View Post
                    And a lot of times voltages don't mean jack either. This plays a HUGE factor on the GM TPI engines. Couldn't get the idle down on my mom's 89 IROC, finally just let it run while adjusting the TPS, once it settled, it was A OK.
                    That's why I put the ~. its serves as a good starting point when it comes to setting the idle. IRC you have to have the IACV unplugged when making TPS adjustments, and afterwards you reset the computer by unhooking the battery. Seems like I read that somewhere, and that's how I set mine last time.

                    320rwhp. 7.67 @ 90mph 1.7 60'

                    DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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                    • #11
                      It wast really dirty. I also swapped the iac for a new one and it made no difference either.


                      Originally posted by That_Is_My_El_Camino
                      I grinned, but I have a sneaky suspicion I'm still gay.

                      Comment


                      • #12
                        Originally posted by fordplay2 View Post
                        It wast really dirty. I also swapped the iac for a new one and it made no difference either.
                        Have you checked the vacuum line going to the fuel regulator?

                        320rwhp. 7.67 @ 90mph 1.7 60'

                        DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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                        • #13
                          There Is also a long vacuum Line that goes from the bottom of the upper intake all the way to the EVAP canister under the air filter. Mine was cracked and rotted.

                          320rwhp. 7.67 @ 90mph 1.7 60'

                          DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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                          • #14
                            Yeah.. everything seems to be ok. That's why I'm stumped. Either I'm looking way to freaking hard for something or it right in front of my face. I'm going to look at all the vacuum lines again in the morning.


                            Originally posted by That_Is_My_El_Camino
                            I grinned, but I have a sneaky suspicion I'm still gay.

                            Comment


                            • #15
                              [QUOTE=91CoupeMike;611633]There Is also a long vacuum Line that goes from the bottom of the upper intake all the way to the EVAP canister under the air filter. Mine was cracked and rotted.[/QUOTE


                              My emissions stuff isn't there. As for that vacuum line, its blocked off.


                              Originally posted by That_Is_My_El_Camino
                              I grinned, but I have a sneaky suspicion I'm still gay.

                              Comment

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