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1991 accord idle surge and some other stuff

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    1991 accord idle surge and some other stuff

    Hello all.

    Looking for some advise on how to diagnose / fix my 1991 accord. Its an EX-R automatic. wagon. (CD9 i believe its called).
    I guess there are a few things.
    1. there is an idle surge which happens after a few seconds of warming up or sometimes right away. it only happens in park so if i change to a gear and sit there with the break on it stabilizes.

    (the following 2 things began occurring after we were messing around unplugging tubes and sensors while the car was running in order to see the effect)
    2. the tachometer is all over the place when idling, it sometimes spiking to 4,5,6k rpm even though the car clearly isn't doing that. the timing of it is not in line with the surging at all it is just crazy random. when in gear its still weirdly unstable but not like in idle

    3. when stepping on the gas while in idle the car gets all messed up, chugging stuttering misfiring. putting on the gas if anything takes away from the rpm and makes the car sound like its gonna die.
    like the tachometer, if i put the car in gear and press the problem isnt as bad but it still stutters a little bit randomly.

    is there something wrong with the computer or what?
    (maybe worth mentioning i deleted the cruise control and air-con recently but it ran OK for a time since then)

    #2
    Idle surge can be caused by a vacuum leak, an issue with the IACV, or the FITV.

    I would start by going through and double checking everything you disconnected and make sure you reconnected it completely and to the correct location. I'm assuming you didn't disturb the distributor ground which is a wire bolted underneath the thermostat housing. Sounds like item 3 may be related to item 2. Does the check engine light come on during any of this?

    A bad (internal leak) Fast Idle Thermo Valve (on the front left side of the intake plenum) usually results in the idle surging up to 1500-2000 rpm and back down, which may get better as the engine warms up. Thread on repairing the FITV: http://www.cb7tuner.com/vbb/showthread.php?t=206012
    90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
    08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

    Comment


      #3
      Originally posted by fleetw00d View Post
      Idle surge can be caused by a vacuum leak, an issue with the IACV, or the FITV.

      I would start by going through and double checking everything you disconnected and make sure you reconnected it completely and to the correct location. I'm assuming you didn't disturb the distributor ground which is a wire bolted underneath the thermostat housing. Sounds like item 3 may be related to item 2. Does the check engine light come on during any of this?

      A bad (internal leak) Fast Idle Thermo Valve (on the front left side of the intake plenum) usually results in the idle surging up to 1500-2000 rpm and back down, which may get better as the engine warms up. Thread on repairing the FITV: http://www.cb7tuner.com/vbb/showthread.php?t=206012
      Hi, thanks for replying.

      I'll answer some of the things you mentioned.

      -We double checked everything is hooked back up.
      -Ive removed and cleaned the IACV and i believe i even swapped it with another car which was working a few years back when i first checked this problem out.
      -There is no CEL
      -Jumping the cable under the passenger side of dash yields no code now, it is simply a solid CEL while jumped
      -Recently it gave a fuel supply system code but now that is gone (43? i think)
      -The problem with surging persists even when the car is warm

      The distributor ground has been disturbed recently, it was actually something i forgot to reconnect and was trying to start the car wondering why it wouldn't start. Then i noticed i forgot to reconnect that so it should be OK now.

      Is there any way i can bypass the IACV temporarily? like remove the housing and just plug the holes to see if the problem goes?

      Comment


        #4
        If you unplug the IACV, it should close; this leaves just the idle screw supplying a little air for the engine to idle. If you want to be sure, I have blocked things like the IACV or FITV with a piece of electrical tape over the holes, the reinstall the valve. It won't idle well at all with the IACV blocked (unless you have a fair vacuum leak elsewhere). Blocking the FITV with a warm engine should make no difference, so if it does, that could be a problem area. Might also check the air boost valve (on the left end of the intake plenum); it is supposed to provide additional air just during starting.
        90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
        08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

        Comment


          #5
          Originally posted by fleetw00d View Post
          If you unplug the IACV, it should close; this leaves just the idle screw supplying a little air for the engine to idle. If you want to be sure, I have blocked things like the IACV or FITV with a piece of electrical tape over the holes, the reinstall the valve. It won't idle well at all with the IACV blocked (unless you have a fair vacuum leak elsewhere). Blocking the FITV with a warm engine should make no difference, so if it does, that could be a problem area. Might also check the air boost valve (on the left end of the intake plenum); it is supposed to provide additional air just during starting.
          Alright, i'll try blocking all three of those things one by one by reinstalling with electrical tape over the holes and come back with the result. Thanks you.

          Comment


            #6
            Originally posted by fleetw00d View Post
            If you unplug the IACV, it should close; this leaves just the idle screw supplying a little air for the engine to idle. If you want to be sure, I have blocked things like the IACV or FITV with a piece of electrical tape over the holes, the reinstall the valve. It won't idle well at all with the IACV blocked (unless you have a fair vacuum leak elsewhere). Blocking the FITV with a warm engine should make no difference, so if it does, that could be a problem area. Might also check the air boost valve (on the left end of the intake plenum); it is supposed to provide additional air just during starting.
            So I tried blocking the stuff, here's how it happened in point form. In the end surge was still present with all three blocked.

            -block the IACV, car runs fine till warmed up (but stays at 2k RPM)
            -about a minute after being warm surge kicks in
            -block FITV car runs ok about 20 seconds, surge kicks in
            -block boost valve, car has troubles starting but does start up, surge is there right away
            -messed around trying to pinch some air lines to see if any in particular affect the surge, nothing
            -unplug the throttle control sensor from the throttle body, car starts sounding super bad and dies
            -plug it back in, start the car, the surge is gone for a good 2 minutes while the car idles (still idling 2k RPM)
            -notice check engine light is on, turn car off to check code, code 7
            -turn engine on again, surge is back, still reading code 7

            Id also note that i think removing the throttle sensor while the car was running is what originally kicked in the super wonky tachometer and the RPM dropping when hitting the gas pedal
            Last edited by dvsblack; 07-26-2020, 01:49 PM.

            Comment


              #7
              1. Sounds like FITV. Open it up and tighten the diaphragm "snug"
              2. Bouncing Tach is an igniter going bad
              3. Is likely o2 sensor and the reason for the code 43 you saw. Replace with NGK/NTK only.

              2 & 3 will definately cause the car to run like crap.
              Last edited by cloudasc; 07-27-2020, 02:46 AM.
              PT3/6 Development Thread | My 1991 LX Coupe | DIY: 90-93 Tcu Fix

              Comment


                #8
                I think you have a massive vacuum leak somewhere. With IACV, FITV, and boost valve all blocked, it should barely idle, not run at 2,000 rpm. What did you use for seals when you reinstalled the IACV originally? What about the seals on the FITV and boost valve? Does your thottle plate close all the way (will it continue to run if you block the throttle body inlet)? Have you messed with the idle screw in the throttle body? Try blocking the PCV port. Have you messed with the EGR at all; a leaking valve or gasket can allow air into the runners downstream of the throttle, IACV, FITV, and boost valve.
                Last edited by Fleetw00d; 07-27-2020, 05:37 PM.
                90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
                08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

                Comment


                  #9
                  Originally posted by cloudasc View Post
                  1. Sounds like FITV. Open it up and tighten the diaphragm "snug"
                  2. Bouncing Tach is an igniter going bad
                  3. Is likely o2 sensor and the reason for the code 43 you saw. Replace with NGK/NTK only.

                  2 & 3 will definately cause the car to run like crap.
                  Thanks, i will try replacing igniter and o2 sensor. I dont think the surge could be FITV because i blocked off the ports going to the FITV with electrical tape and the problem persisted.

                  Comment


                    #10
                    Originally posted by fleetw00d View Post
                    I think you have a massive vacuum leak somewhere. With IACV, FITV, and boost valve all blocked, it should barely idle, not run at 2,000 rpm. What did you use for seals when you reinstalled the IACV originally? What about the seals on the FITV and boost valve? Does your thottle plate close all the way (will it continue to run if you block the throttle body inlet)? Have you messed with the idle screw in the throttle body? Try blocking the PCV port. Have you messed with the EGR at all; a leaking valve or gasket can allow air into the runners downstream of the throttle, IACV, FITV, and boost valve.
                    Never messed with EGR ports yet but i some video suggested drilling them out. i have messed with the Idle screw, ive tried it all the way screwed in and all the way out and multiple ranges in between. currently FITV, IACV, air boost valve... all three simultaneously blocked by electrical tape so it couldn't be those could it?

                    next time im out there ill try blocking the throttle inlet and PCV port (just gotta google what that is first xD)
                    edit: found it, the port on the top center of the valve cover.
                    Last edited by dvsblack; 07-28-2020, 03:53 PM.

                    Comment


                      #11
                      Originally posted by dvsblack View Post
                      Never messed with EGR ports yet but i some video suggested drilling them out. i have messed with the Idle screw, ive tried it all the way screwed in and all the way out and multiple ranges in between. currently FITV, IACV, air boost valve... all three simultaneously blocked by electrical tape so it couldn't be those could it?

                      next time im out there ill try blocking the throttle inlet and PCV port (just gotta google what that is first xD)
                      edit: found it, the port on the top center of the valve cover.
                      Got any friends that Vape? Should have a "party", and use their "clouds" to see if you can find any vacuum leaks.
                      PT3/6 Development Thread | My 1991 LX Coupe | DIY: 90-93 Tcu Fix

                      Comment


                        #12
                        Originally posted by cloudasc View Post
                        Got any friends that Vape? Should have a "party", and use their "clouds" to see if you can find any vacuum leaks.
                        embarrassingly i seem to have fixed the vacuum leak. on the back/drivers side of the PGM-FI inlet thing (not sure that this part was called) there were three open connections where there was supposed to be hoses. i had taken those off when i was doing head gasket and i guess never noticed they were off....

                        car idles OK now but tacho is still off so i guess gonna buy a distributor cheap and replace that.

                        Comment


                          #13
                          Originally posted by fleetw00d View Post
                          I think you have a massive vacuum leak somewhere. With IACV, FITV, and boost valve all blocked, it should barely idle, not run at 2,000 rpm. What did you use for seals when you reinstalled the IACV originally? What about the seals on the FITV and boost valve? Does your thottle plate close all the way (will it continue to run if you block the throttle body inlet)? Have you messed with the idle screw in the throttle body? Try blocking the PCV port. Have you messed with the EGR at all; a leaking valve or gasket can allow air into the runners downstream of the throttle, IACV, FITV, and boost valve.
                          Thanks for the help fleetwood, learned a lot about diagnosing things, i suppose all is OK for now.

                          Comment


                            #14
                            Originally posted by dvsblack View Post
                            embarrassingly i seem to have fixed the vacuum leak. on the back/drivers side of the PGM-FI inlet thing (not sure that this part was called) there were three open connections where there was supposed to be hoses. i had taken those off when i was doing head gasket and i guess never noticed they were off....

                            car idles OK now but tacho is still off so i guess gonna buy a distributor cheap and replace that.
                            Like for the brake booster? Small one for the rear engine mount solenoid (assuming you have automatic trans)?

                            What is the tach still doing?
                            90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
                            08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

                            Comment


                              #15
                              Originally posted by fleetw00d View Post
                              Like for the brake booster? Small one for the rear engine mount solenoid (assuming you have automatic trans)?

                              What is the tach still doing?
                              Hey, the tach was still going all wonky... now its stable until i hit the pedal a bit. reving it makes the tach start going crazy again and the surge starts back up.

                              I tried replacing the igniter and the same thing.

                              After awhile of surging the car will just die and the battery light will be on.

                              disconnecting the alternator seemed to help the problem a bit.

                              on top of this the car has strange electical issues like... the doors will lock outta nowhere on their own.. so i had to remove the fuse for that to prevent keys from getting locked in.

                              if i try to move the power mirrors they move automatically to the left without me pressing anything... so i have to move those manually aswell lol

                              Comment

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