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Idle and throttle bad after replacing tons of stuff. Please help

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    Idle and throttle bad after replacing tons of stuff. Please help

    I have a 88ix. I recently was having an idle issue where it was revving up to 1500 and holding there. I figured this was probably a vacuum leak. I proceeded to replace the following just to be safe and it needed a tune up anyway

    Injectors
    Fuel rail
    FPR
    Fuel filter
    All vacuum lines, boot, etc
    Fuel line going to and from rail
    Cap, plugs, rotor
    O2 sensor <6 months ago

    Now the idle speed is steady at 650-700. The issue now is that while the idle SPEED is perfect, the whole car is bouncing. The exhaust makes a "putt-putt" sound while it idles. When throttle is engaged ever so lightly, the RPMs dip to the point of almost stalling then goes back to normal. I took it for a 5-10 minute drive and it felt as if it was running with half power. This is quite troubling. I've read through many different posts. I cleaned the ICV, throttle body and AFM, still nothing. Checked for vacuum leaks, nothing. Anyone have any other ideas?

    #2
    The most likely cause is intake leaks. A smoke test will find them.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #3
      Double check your plug wires. Sounds like you may have crossed something on the cap.

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        #4
        Throttle Position Switch, there are 2 micro-switches for idle and WOT.

        Sometimes on old engines, engine oil blowby will get into the throttle body and leak down into the TPS and interfere with correct operation.

        This could be a potential problem in your situation, worth checking out.

        Stats are in the Bentely manual.
        www.facebook.com/E30motorwerks

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          #5
          ^
          ^
          That makes sense because when I pulled the intake boot and air box for cleaning, there was a little bit of oil in them. So I will check that out. Thanks for the advice everyone.

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            #6
            So I have tested the TPS among many other things as stated in my original post. I'm still having the same issue. The idle speed is perfect but the engine is "putt putting" and the throttle response is about 50%. I removed each spark plug wire one at a time. Every one resulted in rpm dip then increase except the 6th one which after unplugging the wire at both ends and pulling the plug and placing it on the manifold with wire plugged in it definitely had spark. I checked the voltage going to all the injectors as well as the resistance on the injectors themselves. They are rebuilt ones I purchased a month or two ago. The only thing that is funky is the voltage going to the ICV which read around 6V from each side to the center terminal. After testing everything, unplugging everything, and checking several times I am just about at wits end. I've read about the c191 connector. I've tried unplugging that but it wont come apart. Is there a certain way that it separates? Could it be a bad lead to/from the ECU? Any help/knowledge is very much appreciated.

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              #7
              Did you check your crank sensor too? Pull your ohm meter out & give it a test.

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                #8
                I'm thinking this is a spark issue, the "putt-putt" sounds like a misfire. Did you replace your spark plug wires? Check your resistances in your wires, & triple check to make sure they are correctly coming from the cap to their respective cylinder. Hopefully your cap is labeled for the cylinders bc i've seen some that are blank.

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                  #9
                  Crank sensor is good. All wires are in correctly. What should the resistance be for them? They were all around 6 ohms.

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                    #10
                    I would not look for other causes until I was positive (as proved by a smoke test) that there are no intake leaks. The behavior of the engine as the throttle is opened is most commonly the result of intake leaks. That upset in the AFF can also make the engine run rough.
                    The car makes it possible, but the driver makes it happen.
                    Jim Levie, Huntsville, AL

                    Comment


                      #11
                      The engine runs rough at idle as well as having poor throttle response. I sprayed carb cleaner around every nook and cranny I could think of to no avail. I will try a smoke test next. If I can, I will get a video up here for further discussion. Thanks everybody so far for your input!

                      Comment


                        #12
                        does your engine sound "cammed" at idle? does it pop like it wants to backfire while coasting down hills?

                        probably an intake leak.

                        I had similar symptoms and replaced what I thought were all the vacuum lines, boot, etc along with a bunch of sensors and basic tune up (inspection II) and while the car definitely needed all that, it didn't fix the problem.

                        so did a smoke test and found smoke pouring from the intake side of the oil return tube. replaced the tube with all new parts and the leak/cel/mileage/throttleresponse all were fixed.

                        Faulty oil return tube o rings can increase blow by in the engine as well which will lead to oil in the intake, etc. I had a fair amount of oil in my intake as well as soaking the air filter, etc, which caused some smoke on start up so I thought it was rings/HG/crack but all was fixed w/ a new air filter and oil return tube.

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                          #13
                          Is the oil return tube the one coming from the top of the valve cover and goes to the throttle body? If that's what you mean then I replaced that.

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                            #14
                            The oil return tube goes from the driver's side oil pan to the intake manifold between cylinder 3/4. There are o rings on both the intake and oil pan side that can leak

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                              #15
                              Originally posted by coldweatherblue View Post
                              The oil return tube goes from the driver's side Engine block to the intake manifold between cylinder 3/4. There are o rings on both the intake and oil pan side that can leak
                              fixed, any more confusion search for "bitch tube"
                              Shawn @ Bimmerbuddies
                              Bimmerbuddies LLC
                              717-388-1256
                              2971a Roundtop Rd, Middletown PA 17057
                              bimmerbuddiesllc@gmail.com

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