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m20b25 Idle Woes.... Running out of money...

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    m20b25 Idle Woes.... Running out of money...

    Hey everyone, so a while back I was driving my e30 in the city when I noticed a significant loss of power and throttle lag. Shortly thereafter the motor started vibrating incredibly violently -- enough to shake the whole car, leaving me with a no-start condition. Towed it home and began diagnosing things. Two days before this happened, my cluster started reading my coolant temp incorrectly, but the cluster is also known bad (gauges stick a LOT)

    At first I suspected that I had simply ran out of fuel since I don't trust the ancient fuel sender and I knew I was low, but I soon started hearing the tell-tale signs of the fuel pump's bearings going out. Bingo, or so I thought.

    I've since done a lot of fiddling around, diagnosing things, replacing obviously worn components etc and I've gotten it to the point where it reliably starts, but it idles rough and low at about 500rpm and it sometimes dies on idle when the motor's still cold. At some point it was bucking, surging, and hunting for idle (dropping to almost-stall, then revving to 3000rpm) but that seems to be fixed now. It gets a little better when the car's warmed up, but it's still bad. The car drives like nothing ever happened and the motor sounds healthy when it's not on idle.

    I've probably missed a few things, but here's what I can remember I've done to it:

    - Cleaned ICV, seemed to open/close smoothly but I haven't taken a multimeter to it yet. was insanely gunked up and took almost an entire can of carb cleaner.
    - Replaced and adjusted TPS
    - Replaced spark plugs (old)
    - Replaced distributor cap (tracks even, but old)
    - Replaced rotor arm (old)
    - Cleaned AFM, opens/closes smoothly
    - Replaced coolant temp sensor/blue plug (could only find VDO, only non-OE/OEM part on the car, have heard people had issues with this part?)
    - Adjusted throttle/cruise control cable
    - Replaced fuel filter (old)
    - Replaced fuel pump (grinding noise)
    - Inspected fuel tank, no rust or any debris that could be clogging the pump filter. Old fuel pump filter with 250,000 miles on it (yikes!) looked great.
    - Replaced FPR (vacuum line fouled with fuel)
    - Tested spark, appears to be good (but I do not know quality of spark)
    - Cleaned throttle body
    - Replaced ICV hose
    - Replaced valve cover breather hose
    - Replaced clamps on all vacuum hoses
    - Epoxied the metal vacuum fittings onto the throttle body
    - Accidentally snapped the wire off my impulse sensor on the spark plug wires while I was doing the cap and rotor like a tard
    - Attempted to check fuel pressure on the rail, but the fuel line's end was pretty rotted so I gave up -- How hard is this hose to access/replace? Is there enough slack to slice the end off?
    - Attempted to stomp test, but the car won't stomp. TPS/cables are adjusted and confirmed good, assuming I have an old ECU (1988 model, it could go either way depending on production date)
    - Bled coolant when I needed to

    I am running out of culprits and I still don't know what's going on with the car. I'm also running out of money, this has burned through my savings and driving is my only option to commute. Car is throwing a CEL, but I can't stomp to see the code and I can't find a place to rent me a code reader that will work on this car.

    Also another thing, the car revs when I spray carb cleaner on the left side of the throttle body indicating unmetered air is getting in somewhere over there. The problem is, I've already sealed up the metal fittings, replaced the ICV hose, replaced the crankcase breather hose, so there shouldn't be anything else that can possibly vaccum leak over there can there? WTF? The only other thing over there I can think of are three coolant hoses.

    The only things left I can even think that could be causing this are the ICV, ECU, or the fuel injectors. I'm almost so out of things to diagnose that I'm beginning to suspect very unlikely things like a skipped tooth on my T-belt. Any ideas? I'm grasping at straws here and both of the local mechanics I've had recommended to me never returned my calls.

    Bonus points if anyone who reads this lives vaguely around the Seattle area who has a known good ECU or ICV I could test out, or one of those Peake code readers. I can probably get the car to you, worst case I just give you collateral or cover your gas and lunch to come out to me.
    Last edited by Sehnsucht; 06-14-2015, 03:15 PM.
    1988 Lachs 325is

    #2
    I think you have found your problem already. Google for a DIY smoke machine and check for vacuum leaks since you are out of money.

    Comment


      #3
      Originally posted by dnguyen1963 View Post
      I think you have found your problem already. Google for a DIY smoke machine and check for vacuum leaks since you are out of money.
      Do you know if those coolant lines on the left side of the throttle body hold vacuum pressure? I don't even know where the leak could possibly be coming from. I replaced the ICV hose with OE bmw, the crankcase breather hose with OE bmw, epoxied the metal fittings on, replaced the hose clamps on every hose..

      Is there anything else that could vacuum leak on an m20 in that general vincinity? I've already replaced everything imagineable over there short of the coolant lines. Not super familiar with m20's yet though, still learning this motor -- is there anything I didn't mention which could vac leak there?

      How about the little gasket between the metal plate the coolant hoses hook up to and the throttle body, is that a spot which can vac leak? what would this gasket be called if I want to replace it? What about the intake manifold gasket?

      Should also mention intake boot had a film of oil on it, but who knows how long it's been there for -- car's 250k and this is my first time around in there.

      I understand some e30's have different throttle body setups.. I have a 1988 325is, and I can take a picture if it would help.

      Wouldn't be surprised if there's a vac leak hiding somewhere -- car was garaged it's entire life until I bought it, so all the dry rotted hoses are starting to crack from the expanding and contracting last winter. Everything rubber has to go at some point.

      I could come up with another $100-200 for parts to fix this before I'm scraping the bottom of the barrel, after that it's time to find a new job I can bus to or something. Welp at least I'll have a garage next month...
      Last edited by Sehnsucht; 06-14-2015, 06:50 PM.
      1988 Lachs 325is

      Comment


        #4
        BIG UPDATE: The little vac hose on the bottom of the throttle body was dry-rotted and barely hanging onto the nipple. Cut the end off of it and zip-tied it back in place. No more identifiable vacuum leaks. Idle is still 500-550rpm rough and it sounds like it's misfiring on a cylinder now, so I think I'm looking at a spark issue. Might have just not seated a plug right -- shop sold me the wrong plugs so they came on and off like 5 times the day I did them so hey maybe I rushed the job.

        Any idea what that vacuum hose is called so I can replace it? This temporary fix has it sealed up, but the rubber is dry rotted BAD...
        1988 Lachs 325is

        Comment


          #5
          The intake boot probably has a crack or two as well, especially if it's got oil in it. May seem fine, but at $30, you can't really go wrong.

          Comment


            #6
            E30 has many places that can leak. The only proper way to find them all is to perform a smoke test at about 2-4 psi and a plugged exhaust. You would be surprised to see how many places the smoke can come out of your leaky engine. Good luck. If you want to know part number, go to www.realoem.com.

            Comment


              #7
              Originally posted by Sehnsucht View Post
              BIG UPDATE: The little vac hose on the bottom of the throttle body was dry-rotted and barely hanging onto the nipple. Cut the end off of it and zip-tied it back in place. No more identifiable vacuum leaks. Idle is still 500-550rpm rough and it sounds like it's misfiring on a cylinder now, so I think I'm looking at a spark issue. Might have just not seated a plug right -- shop sold me the wrong plugs so they came on and off like 5 times the day I did them so hey maybe I rushed the job.

              Any idea what that vacuum hose is called so I can replace it? This temporary fix has it sealed up, but the rubber is dry rotted BAD...
              5/16 inch (ID) fuel line, low pressure. It's actually not a vacuum hose, it's the charcoal canister gas vapor purge line from the solenoid. You'll need a couple of hose clamps for it. The original one has a wide rubber cover on one side, but it's not required.

              Comment


                #8
                Seriously though man, smoke test that b*tch. Fixing vacuum leaks on stock engine management makes her run soooooo much better. All e30's that have not been well maintained their whole life have vacuum leaks. Every single one. A smoke tester will not break anyone's bank. Grab a rubber glove, some rags, a few feet of tubing to blow into, and your favorite smokeable. Plug the muffler with rags, prop the throttle wide open, remove the AFM, stab a small hole through your rubber glove, and insert one end of the tubing. Make her air tight. Now wrap the rubber glove over the intake boot. Also air tight. Light up your smokie and start chiefin'. Blow the smoke into the tubing. It'll take a minute or two, but eventually you will fill the intake with smoke and it will start leaking out of the problem areas. This method hasn't failed me yet with a problematic car, so I'm confident in its magic. Try it and be amazed with what you find.
                1989 325i Lachssilber Sedan
                5-Speed Swapped
                M30B35 Swapped
                MegaSquirt MS3X

                1987 325i Lachssilber Sedan
                260k OEM Automatic Daily Baby

                Comment


                  #9
                  I've never gotten my E30 high before. Do you think it might fry its ECU?

                  Comment


                    #10
                    Originally posted by packratbimmer View Post
                    I've never gotten my E30 high before. Do you think it might fry its ECU?
                    :D Temporarily
                    1989 325i Lachssilber Sedan
                    5-Speed Swapped
                    M30B35 Swapped
                    MegaSquirt MS3X

                    1987 325i Lachssilber Sedan
                    260k OEM Automatic Daily Baby

                    Comment

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