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OK I give, need help getting my car to run right

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    OK I give, need help getting my car to run right

    I didn't know if I should put this in the M20 forum or here, sorry if its the wrong place. Either way I'll try to be as brief as I can while still being thorough...

    I got my 5-speed '91 325i 3 months ago, its my first BMW. I've spent a bunch of time and money trying to get it to run right, and just about everything I have done has helped to some degree, but now I'm commuting 65+ miles a day in the car and I need to try and speed up the process without just throwing more money at it.

    So far I have replaced plugs (NGK copper), cap & rotor (Bremi), O2 sensor, crank sensor, injectors (reman M50 greentops), fuel filter, all underhood fuel lines, exhaust manifold gaskets and performed a valve adjustment (I even bought the proper eccentric tool). After replacing the breather hose, VC gasket and rocker shaft seals it has no sign of vacuum leaks when hooked up to a smoker. The pedal test brings up nothing, and no codes are present when hooked up to my roommate's Snap-On Modis scanner. Temp sensor and AFM both test within spec, though admittedly the instructions AllData gives for testing the AFM made little sense so I may have screwed that up. I have not performed the AFM test where you use the 9v battery.

    The worst symptom it has right now is slow, choppy acceleration. As rpms rise above 3500 it begins to be very choppy, lots of hiccups through the rpm range. If I give it much more than half throttle when taking off, it feels like it goes VERY rich and just bogs down and makes no power at all, you have to roll into the throttle. Sometimes if I push the accelerator down further, it actually makes the car accelerate slower. Left turns and highway on-ramps are not my friends right now. When I first start the car cold, I have to roll into the throttle really slow and rev it once before I try to take off, otherwise the car will want to stall and I can smell raw fuel. When decelerating under engine braking, it will lunge forward every second or two. I also think it is doing a subtle on/off sort of thing, possibly a misfire, it feels like its always in a constant cycle of slight accel/decel when cruising at a constant speed, but it might just be wind or bumps... or in my mind. Its just really inconsistent in the way it runs, some days it seems to run much better than others, and also occasionally the idle gets all erratic revving between 1100 and 1400rpm (it normally idles around 1100 which from what i have read is high). The car gets poor mileage and is very slow in general, I was kind of expecting this car to be a bit quicker then the Dodge Neon it replaced, but it isn't even close to the performance I am used to. Despite all of this, it still managed to pass CA smog by a sizable margin.

    So, what should I try next? AFM? Coil? Plug wires? Should I try playing with the AFM? It appears to have already been opened up at some point as the cover looks to be held on with hot glue or silicone.

    Sorry for the novel, I know I said I was going to be brief.... Thanks a bunch in advance everyone.
    sigpic
    1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

    WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

    #2
    Have you tried letting it run in the dark to see if the coil or wires are arcing. Might also try a fuel filter.
    Current
    99 328i (Sold)
    91 318is M50B25TU
    89 325ix (Parted out)
    87 325is (Parted out)
    95 525i (Parted Motor for 91 318is)

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      #3
      I suspect that your fuel injectors are mis-behaving. It is dumping way too much fuel during acceleration.

      Comment


        #4
        If the AFM has been tampered with, that would be my first suspect. You can open it up and "tweak" it by twisting the spring inside, but I have a feeling someone just caused the mixture to become over-rich.
        Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

        Elva Courier build thread here!

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          #5
          I have not looked to see if the coil wires are arcing, I will check that tonight. Is that an indicator or a faulty coil or some other problem?

          I may have failed to mention it, but I did replace the fuel filter. I also failed to mention that I cleaned the injector harness under the intake and the main engine harness on the firewall using the proper Wurth micro-files and added dielectric grease. Cleaning those connections provided a noticeable improvement.

          The car runs A LOT better with the M50 injectors compared to the stock, presumably original units. Symptoms were greatly reduced upon performing that swap, the only thing that helped it more was the cap/rotor.

          I have been meaning to pop the cover off the AFM and see if there is any sign of previous repair or modification, haven't got to it yet. Do any of you have any experience with the reman Cardone AFMs?

          Thanks so much fellas.
          sigpic
          1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

          WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

          Comment


            #6
            The odds are that the ignition wires are original. Replacement interval is every 10yr/100k. So I'd replace those. Also check the TPS and check the rail fuel pressure.
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

            Comment


              #7
              TPS checked good according to Alldata procedure (or did we use the Modis?), but that was right when I first got the car so I will check again. TPS on this is just switches for WOT and closed, right?

              Fuel rail pressure is good, it had a gauge on the rail when I got it but had to pull it for smog.

              I'll look into ordering a set of wires, and particular brand you guys like? I want something decent but inexpensive, don't need fancy.

              The car sat for 2+ years with a bad trans before I got it, and I have a feeling that leading up to that a lot of maintenance was not neglected but "it still works so why swap it" causing me to now have to play a lot of catch up.

              Thanks again.
              sigpic
              1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

              WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

              Comment


                #8
                Just listened to the TPS. Good audible idle click, I hear something at about 70% but it is a much quieter sound with a lower, dull tone. About to check it with the meter.

                Opened up the AFM and not sure if it actually was tampered with previously, well, provided Bosch use a nasty super glue-like substance to keep AFM covers on. The contacts do appear to be very worn though and the flapper door seems to be flopping around more loosely than I would expect, though admittedly my experience with these old Bosch AFMs is limited.

                Please excuse if it seems I am replying to myself, part of why I am typing this here is to remember it myself, and maybe my notes can be useful to others in the future. *shrug*
                sigpic
                1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

                WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

                Comment


                  #9
                  I too used to think a "click" from the TPS means you're good to go.
                  Been battling a random idle surge/up-down for a month and finally just bought a new TPS; problem solved.

                  When you performed the stomp test, are you saying you have no codes from the CEL blinks? Or you aren't getting any CEL blinks at all to tell you anything?

                  Have someone let you swap ECU's as well to rule that out. That being said, I love your car and almost bought it in 2008ish, but couldn't be bothered driving to Arizona :p

                  1991 325iS turbo

                  Comment


                    #10
                    Just confirmed TPS with meter, everything indicates its a-ok.

                    Yeah, no codes in the CEL blinks., which corresponds with no codes on the Modis.

                    Just tried adjusting the AFM spring to the lean side since everything indicates it has been running rich and now I have a CEL. But that CEL may be from when I accidentally started the car with the IAC disconnected. Will a disconnected IAC result in a CEL? Will that CEL remain until I disconnect the battery? (or x number of key cycles?) Adjusting the spring seemed to put the wiper closer to where it should be at rest, closer to the 1st trace off the resistor strip instead of the 2nd. I guess I'll try disconnecting the battery before I put the AFM spring back how it was. If the AFM gives me much more trouble I will break down and buy a refurb one from Bavarian Restoration (unless you guys think there is a better option).

                    Everyone seems to love my car more than I do. lol I mean I like it, it just ended up being way more of a project than I wanted to take on or can afford. My Neons fit my budget a lot better and NEVER gave me troubles like this, lesson learned, too late to turn back. I have far more money into this car than it is worth and I still have a LOT more to do before it is right.

                    Thanks again.
                    sigpic
                    1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

                    WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

                    Comment


                      #11
                      I have determined the AFM wiper was out of from position due to the spring being one tooth off, moving it corrected the flapper to rest at the correct location and the car seems to be running a lot better even after just one drive after disconnecting the battery. It still feels a tad rich under certain load conditions in the upper range, but I have access to a couple chassis dynos so I'll get it on rollers with a wideband before I do any more tweaking. Will order plug wires and if I feel I need to after playing with it some more will get a refurb AFM. I may still bend the AFM wiper to a new section of the resistor strip but right now it seems to be running through the rpm better than ever.

                      Thanks to all for the suggestions and confirming I am on the right track. Holy crap this thing will break the tires loose now!
                      Last edited by Vincent Brick; 07-30-2014, 05:25 PM.
                      sigpic
                      1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN

                      WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack

                      Comment

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