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Help, at wits end with my 91/325i m20 Cold Outside Temperature related misfire/hesita

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    Help, at wits end with my 91/325i m20 Cold Outside Temperature related misfire/hesita

    Hi all, hopefully someone has had a similar problem I am having recently. I have searched and read many, many, threads and have not found a solution.

    I am the original owner of a 91 325i daily driver with about 270k. About a year ago 9/2017, I has a small fuel leak from the return line from the FPR sprayed gas onto the area above the thermostat housing which burnt my wires and melted my CTS (Blue plug). Developed rough running when the engine is hot, stalling at lights,etc. and it threw a CEL was unable to do a stomp test. So I changed and adjusted the TPS, then I got a 1222 and 1223. So I also spliced in a new FI plug to the harness and replaced the CTS. I also replaced the ICV because the ohms between the terminals were off. The car ran fine for the past year through the winter of 2017 and spring,summer and fall of 2018 without a problem.

    Almost 1 year later 9/2018 I get a CEL when I come to a stop after highway speeds, and when I pull away the CEL goes away. Stomp test = 1222, I check for vacuum leaks, my intake boot has a slight crack, so I change that. while it was out I also cleaned out the the ICV and the AFM and the throttle body. sprayed throttle body cleaner all over and also found a leak at the intake manifold. So I replaced the manifold gasket and also the six lower injector o-ring seals. Car runs fine for a few week when the outside temp is about 45f. No CEL code stomp test 1444.

    But now its getting even colder outside low 30's to 20's. So when I start in the AM the first time. I get it to turn over without a problem, but I get a very rough idle / hesitation / misfire and sometimes stalling. It takes a few minutes and when the engine warms up a little it idles fine and settles down. I warm up the car for about another 5 to 10 minutes and the temp gauge reaches 1/4 to 1/2 point and I drive away and things are fine for a few minutes. As the cold outside air cools the engine down or flows into the engine bay at speed, it cools something down to the point where I get hesitation / misfire and rough a idle again. I can pull over and let it idle for a few minutes and then it settles down again. I drive away again and if its very cold outside it happens again after a few minutes at highway speeds. This does not happen if its cold outside and wgen i am in stop and go traffic. I believe that everytime I stop at a light it warms whatever the issue is and I do not get the hesitation / misfire etc... If its warm outside like in the 40's It will not happen and I can go from A to B without pulling over to allow whatever to warm up again.

    So here is what I have done so far, no CEL Stomp test 1444

    I pulled the DME connection and checked the resistance at points 24 and 45 for CTS and its within the normal values as per Bentley manual hot and cold. I redid the splice at the CTS / FI plug with solder. Checked the ICV resistance and it was all WNL

    I had a 75c thermostat installed 5 years ago and though it might have been stuck open and as the car was going down the road it cooled the CTS down and caused a change in the open/closed loop of the DME control. I changed that to a 80c thermostat without any changes.

    Tried a remanufactured AFM, installed a new FPR, new O2 sensor, six new bosch copper plugs gapped at .028, new valve cover gasket, new rotor, new distributor cap, new crackcase vent tube and a new fuel filter. Checked C191 and looks ok, wiggled all the wires that I could when the car is in the hesitation / misfire mode and nothing, no changes.

    So I stress this is temperature related issue. When cold = hesistation / misfire
    / bad idle. Engine warms up and idles fine and purrs like a cat. drive away when its cold outside, engine cools down and hesitation / misfire returns. Pull over and let the engine warm up again for about 5 minutes and I am able to drive away without any problems untill it cools down again. Does not happen in stop and go traffic because of all the time stopped at lights and allowing engine to warm whatever up preventing hesitation / misfire.

    Thanks in advance for all your input and help!!!!
    Last edited by DaveH91e30; 12-08-2018, 06:32 PM.

    #2
    The colder an engine, the more fuel it needs. Since your temp sensor specs fine and you have no vacuum leaks, I'd check fuel pressure / injector spray pattern or anything air / fuel ratio related.

    Have a known good AFM? How old is your fuel filter? O-rings on vent tube still good? Valve cover vent hoses get old and crack. Brake booster hose? Anything that allow too much are or not enough fuel.

    Good luck.

    Comment


      #3
      Originally posted by e30sh View Post
      The colder an engine, the more fuel it needs. Since your temp sensor specs fine and you have no vacuum leaks, I'd check fuel pressure / injector spray pattern or anything air / fuel ratio related.

      Have a known good AFM? How old is your fuel filter? O-rings on vent tube still good? Valve cover vent hoses get old and crack. Brake booster hose? Anything that allow too much are or not enough fuel.

      Good luck.
      I have changed the FPR, Valve cover vent hose, fuel filter, checked the brake booster hose. Swapped AFM with a known good one (no cure to the problem) went back to the original AFM after a few days without any change. Now the vent tube (I assume your talking about the aka bitch tube) I did not change the O-ring on the top, looked ok when I had the intake manifold off to change the gaskets. At the time I did not think about the lower o-ring seal. But I have rotated the tube and made sure its seated into the manifold.

      But like I said, at initial cold startup, I get the hesitation/misfire/etc... after a few minutes it settles down, and I follow that with at least another 5-10 minutes of steady idle without any issue. Once I drive away, in a cold climate (less than 40f) after a few minutes of travel going 40-60 mph, the hesitation returns. I can pull over sit for about 5 minutes and then pull away and I get a few minutes of strong acceleration, without any issues. If the climate is really cold outside the hesitation will return. So on really cold days, I look to take the stop and go traffic route to my destination, which allows me to stop at traffic lights which allows the component at fault somewhere in the engine compartment to warm up and function correctly.

      Still banging my head on this one!!!
      Last edited by DaveH91e30; 12-09-2018, 01:06 PM.

      Comment


        #4
        Yes the bitch tube. That's probably not it but couldn't hurt.

        Tried a know good DME?

        Did you check fuel pressure or just replace the FPR? How old is your fuel pump? I had a high load running issue on my M42 and it turned out to be the fuel pump not supplying enough volume.

        Have you cleaned all the engine harness grounds / + junction block...couldn't hurt.

        Oddball things. Warped valve cover. I've seen a few on overheated cars. 90 degere fitting(s) on the throttle body. Anything that will allow unmetered air and let it run lean.

        Comment


          #5
          Check c191 and looks good, original harness, the only thing that is new is the FI plug I had to splice in when I had the fuel leak issue a year ago. The readings cold, warm, and hot at the dme is within normal limits.

          Changed the valve cover gasket, no signs of oil around the cover and getting into the spark plugs.

          Roated the bitch tube and no signs of oil there also.

          Fuel pump was changed about 8 years ago, I didn't check the the pressure was with a guage, I just got a new one and installed it. No changes in correction of the issue.

          I also bleed out the thermostat housing with the front of the car up on jacks. To make sure I had coolant in the thermostat bathing the senors.

          All 90 degree joints are solid

          I don't have a know dme to try though...

          Comment


            #6
            Did the fire melt the plastic housing protecting the injector harness? The top half is easy enough to change.

            Have you swapped in a new main relay...the 5 pin one on the shock tower?

            Comment


              #7
              The harness cover is slightly deformed, but not to bad. I did take it apart to check for any issues. None was noted. As for the relay, no I have not changed that or tested it. But I don't think it experiences to much of a temperature change since it so far away from the engine.

              Comment


                #8
                You did not mention if you changed the coil.

                My suspicion is that the coil heats up and causes the issues you are experiencing, then when you idle the car for about 5 - 10min, the coil cools down (Contrary to what you suspect). Try wrapping the coil with a damp cloth the next time you experience the problem and see if that helps your immediate situation.
                1990 325i
                2004 330i Individual 6-speed
                sigpic


                Comment


                  #9
                  Get your timing light out and hook it to each plug wire. Observe the flashes on each one. See if you note any patterns.

                  Comment


                    #10
                    Originally posted by IceWhite View Post
                    You did not mention if you changed the coil.

                    My suspicion is that the coil heats up and causes the issues you are experiencing, then when you idle the car for about 5 - 10min, the coil cools down (Contrary to what you suspect). Try wrapping the coil with a damp cloth the next time you experience the problem and see if that helps your immediate situation.
                    But how would that explain the hesitation/misfire/rough idle the 1st time I start the car in the AM when its cold outside. The coil should be as cold as everything else.

                    Comment


                      #11
                      Extreme temperature?

                      Mmm... Didn't see that in your opening post.

                      I wish I could help!
                      1990 325i
                      2004 330i Individual 6-speed
                      sigpic


                      Comment


                        #12
                        Keeping my fingers crossed!!!

                        Keeping my fingers crossed, I might have licked this problem!!! going to give it till tomorrow AM when the whole thing is super cold and lets see what happens!!!

                        Comment


                          #13
                          Which part fixed it?

                          Comment


                            #14
                            Originally posted by DaveH91e30 View Post
                            Keeping my fingers crossed, I might have licked this problem!!! going to give it till tomorrow AM when the whole thing is super cold and lets see what happens!!!
                            Curious as well, my E30 has a very rough idle when cold, smooth when warm,i would like to figure it out as well.

                            Comment


                              #15
                              Keeping my fingers crossed!!!

                              After some more searches and reading of the threads here about similar hesitation/misfire, etc... problems, The only other sensor I have not looked into is the CPS (Crankshaft Position Sensor) located on my m20b25, bottom front passenger side, by the A/C compressor. At the DME pins 47 and 48 my CPS reads within spec (530ish ohms). Reading into the sensor and its function, how it works, whats its supposed to do, etc... its just a simple magnetic pulse generator. Apparently there is a magnet in the sensor and as the cogged flywheel spins in front of it, which generates the impulse through a coil in the sensor. An A/C current (I think), is then transmitted up to the DME as an A/C voltage. Which then the DME uses to determine air/fuel ratio, timing, etc...

                              Although I did not have any CEL that would indicated that my CPS (would have been stomp code 1243) is dead or really badly out of range since the measurements at the DME was normal. I have learned that the DME has the ability to run in a preset "limp home mode" if a sensor signal if not within normal range that it's supposed to be in, but still not dead (dirty signal). So going back to the DME harness I rechecked all my values with a multimeter and all of them were still WNL.

                              One of many solutions mentioned on the threads was to clean the CPS and/or replace it. At first I was unable to remove the CPS in fear of striping the head of the 5mm hex bolt (all I had was a short 5mm Allen key), to get to it and really give it a good clean. But I was able to give it a good spray with throttle body cleaner and wipe it down well, it was original and had 27 years of gunk on it. I would take on the challenge of removing the bolt in case I needed to replace it, and deal with routing it around to the area of the water pump pulley and up to the round service port, if/when needed with a proper 5mm hex in a socket or something like that.

                              I have to say that after I cleaned the CPS I DO NOT have anymore hesitation/misfire/rough idle issues when its cold outside anymore!!! it's about 20f outside and it started right up and idles fine today. Drove around all day in the cold and not one sign of problems at anytime...

                              I don't know what 27 years of gunk on the sensor would do and how the ambient cold temperature plays a role in this. But not really doing anything other that spraying it with a throttle body cleaner and wiping it down while it was still bolted in seems to have fixed my issue. Perhaps the sensor was just dirty and prevented an ideal impluse or grounded out because of the gunk and condensation that might have formed on the metal barrel and not sending a correct voltage up to the DME, which then messed with the air/fuel/timing calculations. Somehow the cold ambient air temp would contribute to its malfunction. The sensor was original, it looks like the entire front part of it was made or covered in some type of metal. Looking at replacement CPS, there are a few and "OEM" ones (expense) that look like the one I have installed with a metal barrel in the front. There are also ones that dont look like that, covered in plastic with a small metal pin in the front.

                              Perhaps the gunk on the metal part of the sensor somehow prevented its correct signal (within range, but dirty) to be sent to DME and it chose to run on the "Limp home mode" by inserting preset values into the air/fuel/timing calculations causing the hesitation/misfire/rough idle...

                              I have ordered a new CPS anyways to keep on hand if this ever occurs again. I am just going swap it next time!!! So measuring the ohms on pins 47 and 48 and getting normal values are not a sure way to confirm that the CPS is working. Cleaning it to start and then swapping it out for a know working one would be the better way to testing its correct function. It's just another thing like the icv/afm to keep clean regularly I guess now...

                              I consider this solved!!! Hopefully!!! Keeping my fingers crossed!!!

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