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87 Celebrity 2.8L idle surging and stalling

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    #16
    MAP and MAF are two different words. Again, does it have a MAP on the firewall?

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      #17
      Originally posted by EternalArianne View Post
      It idled fine for 5 mins or so then started surging up and down....
      Years ago, I got a new China built ECM on a 88 or 89 Berreta with 2.8-V6 engine..I had two of them....and it had similar behavior as yours has now.

      I removed it, and installed OEM ECM...problem went away. You might take a look at your ECM, and see if its OEM. IIRC, its underneath the coils...I can't recall if I had to remove the starter to have some space. I think I had to remove oil filter's housing to remove starter. Maybe your vehicle has more space, and removing starter and oil housing is not needed.

      You might find a Junk Yard ECM

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        #18
        Originally posted by 85_Ciera_Rebuild View Post
        Years ago, I got a new China built ECM on a 88 or 89 Berreta with 2.8-V6 engine..I had two of them....and it had similar behavior as yours has now.

        I removed it, and installed OEM ECM...problem went away. You might take a look at your ECM, and see if its OEM. IIRC, its underneath the coils...I can't recall if I had to remove the starter to have some space. I think I had to remove oil filter's housing to remove starter. Maybe your vehicle has more space, and removing starter and oil housing is not needed.

        You might find a Junk Yard ECM
        You must mean ICM (ignition module). I?ve had many bad ones over the years but never a surging problem. Not saying it can?t happen.

        Don?t need to remove the starter, unless you drop a bolt. I use a 6 point socket to help prevent the bolt from falling. Do remove the cooling fan, it?s so much easier, and disconnect the battery since you?re so close to the starter. Hardest part for me is that bracket that the spark plug wires attach to. I use a u joint to get that nut and bolt out.

        BTW the ICM is the most common thing I?ve had fail on these cars. Nice to have a spare anyway.
        1989 Celebrity CL 4 door, 3.1 MPFI, 4 speed auto, summer daily driver
        1989 Cutlass Cruiser wagon, 3.1 MPFI, 4 speed auto, special summer ride
        1996 Cherokee XJ 4 door, 4.0, 5 speed, winter daily driver & towing vehicle
        1991 Tracker 2 door, 1.6, 5 speed, needs work
        Previously several Celebritys, 6000s, & 2 U-vans

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          #19
          Oh I?m sorry I misread. It does have a MAP sensor. I?ve tried unplugging it and it throws all kinds of error codes but idle doesn?t change. I also tried plugging the vacuum line to the MAP, still no change.

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            #20
            So this is what I would do...

            I would pull the upper intake plenum completely off the car. Its a pretty easy process. Recheck/Replace all the plenum gaskets, EGR gasket, Throttle body gasket, PCV hose (<---Especially this one), PCV Valve, replace the FPR, and check over very carefully the 2/3/4 way vacuum plug at the throttle body. While in there, I would OHM check all the fuel injectors.

            One of these I feel is the culprit, but I am not there to say which way I feel strongest about.
            Brian - Carpe Diem

            I dont have to love my president, or any god, to love my country!!
            More people have died in the name of "God" than in all wars combined thruout history
            01 Pontiac Aztek GT AWD 127k - 04 GMC Envoy SLT XUV 193k

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              #21
              Originally posted by tlc1976 View Post
              You must mean ICM (ignition module).
              ECM is a generic expression, ICM is specific to a function. Like the word humans covers all humans, and "Mexican" is a subset of humans.

              OP - Injector o-rings need to be replaced, as an engine ages. I would replace them with each used vehicle I've bought, along with intake manifold gasket. When a cold engine is fired up, computer runs on a default program...then after 5 minutes or so, it switches to its other program (closed loop)

              Open Loop After Start Up.

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                #22
                O-rings and strainers came preinstalled on the new flow matched injectors I installed. I had to remove the plenum to do all of that and inspected the PCV hose (and replaced the PCV valve itself). The plenum gasket kit included a throttle body gasket as well.

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                  #23
                  Originally posted by 85_Ciera_Rebuild View Post
                  ECM is a generic expression, ICM is specific to a function. Like the word humans covers all humans, and "Mexican" is a subset of humans.

                  OP - Injector o-rings need to be replaced, as an engine ages. I would replace them with each used vehicle I've bought, along with intake manifold gasket. When a cold engine is fired up, computer runs on a default program...then after 5 minutes or so, it switches to its other program (closed loop)

                  Open Loop After Start Up.
                  Ok no problem. In these cars I always understood ECM to be specifically the engine computer.

                  OP- Running out of places to check. Another possible leak could be the transmission modulator. It?s fed by the thin metal line with rubber couplings that goes from the front of the throttle body down along the block to the modulator (round metal can) sticking out the front of the transmission. Remove the clip on the corner of the block, disconnect the line and cap the throttle body and see if it changes. The car won?t shift the same but just for checking. I?ve had them leak before and suck trans fluid into the throttle body.
                  Last edited by tlc1976; 02-16-2021, 10:55 PM.
                  1989 Celebrity CL 4 door, 3.1 MPFI, 4 speed auto, summer daily driver
                  1989 Cutlass Cruiser wagon, 3.1 MPFI, 4 speed auto, special summer ride
                  1996 Cherokee XJ 4 door, 4.0, 5 speed, winter daily driver & towing vehicle
                  1991 Tracker 2 door, 1.6, 5 speed, needs work
                  Previously several Celebritys, 6000s, & 2 U-vans

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                    #24
                    Again, the newly installed China built ICM was the issue on mine...2.8 V6 was a darn good engine...I had two of them...very high milers.

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                      #25
                      Update: I found this info on a F-body forum: https://www.thirdgen.org/forums/tpi/...crew-must.html

                      see the section Throttle Minimum Air Position Adjustment.

                      After doing that process, that I have eliminated the idle surging entirely. Im still getting the code 45 rich exhaust but I?m willing to deal with that since this will be mainly a utility vehicle. I just didn?t want it to surge and stall on me when I?m hauling stuff around.

                      Thanks everyone!

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                        #26
                        Originally posted by EternalArianne View Post
                        idle surging
                        On EFI based redblock Volvos, throttle plate must be at OEM specs. Earlier years did have a bleed air adjustment for setting idle RPM, but this was eliminated...I suspect due to "thumbs nuts'" screwing the idle pooch at Volvo service centers.

                        IAC performance is dependent upon factory CFM flow spec at idle RPM; IAC is not required above idle, and power to IAC valve is turned off when throttle plate is moved past idle position on EFI Volvos. On Volvos, when CFM flow spec is exceeded, it idles at a faster RPM...

                        GM most likely, used throttle position sensor to inform ECM(s) the accelerator peddle is at idle position. So, TPS voltage needs to be checked. If TPS voltage is at idle, then IAC would be engaged.

                        On both of the 2.8 V-6's I had, they both were fine at idle, but I did install new injector o-rings, cleaned throttle plate, and related gaskets, and never messed with twitching throttle linkage, etc. So, the OEM spec for CFM airflow was within factory spec.


                        So tell me, was the OEM CFM (cubic feet per minute) spec exceeded, or less than OEM spec?

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                          #27
                          I?m not sure about the CFM as I don?t have a diagnostic scanner at all, only a code reader. I?m sure there could very well be other issues but for now I?m just glad the surging and stalling is gone.

                          As you said, these 2.8L V6 engine are resilient. Everyone I?ve talked to says how good these motors are, probably a testament to how it even runs at all after sitting for years and having over 200K miles on it lol

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                            #28
                            Originally posted by EternalArianne View Post
                            I?m not sure about the CFM
                            Question, in plain English...sucking too much air, or less than OEM spec that was causing the surging?

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                              #29
                              I honestly don?t know, since this is the first time that I have personally had the car running correctly so I don?t know what it should be or was before it sat for many years. I have no doubt there could be other issues going on but for now it will suffice. I?ll probably do a full tear down and rebuild once I have plenty of cash to throw at it, as it needs some body work as well.

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