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Thread: 1984 733 125k sudden very rough idle and impossible to drive

  1. #1
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    1984 733 125k sudden very rough idle and impossible to drive

    1984 733 with 125k
    Driving normally then sudden very rough idle and impossible to drive.
    I was driving around town. The car seemed to be running normally.
    There are two stop lights close together. I waited at the first one, car idling normally.
    Second one turned red as I approached so I stopped and the car immediately started running rough.
    It didn’t stall but I had a problem even getting it off the road and into a parking lot.
    Car starts and runs but runs extremely rough, misfiring and rough exhaust note. Smoothes out some at 2000 rpm but definitely not running right.
    All six spark plugs are black and wet. Obviously running way too rich.
    Cleaned the plugs, made no difference.
    When this happened the car was at normal operating temperature and I did not re-start it.
    Although it is possible it is the thermo time switch or cold start valve, it seems unlikely. As neither should have been operating.
    I replaced both the AFM and fuel pressure regulator several years ago. The fuel pressure regulator holds vacuum and there is no black smoke from the exhaust. The fuel return to the tank is not blocked.
    The ICV clicked when the ignition was turned on.
    It did not hum or vibrate as Bentley says it should.
    I took it off (VDO, probably original) and cleaned it with carb cleaner. It was full of black oily stuff.
    There was no discernible movement of any internal mechanism in the ICV when you shook it or twisted it, before or after cleaning.
    (A post on this board from bmwdirtracer in 2010 said you should be able to hear the mechanism inside operate when you turn or twist it.)
    Installed it, no difference, very rough idle.
    No difference if the electrical connection is connected or not connected.

    Black, wet spark plugs, obviously too much fuel.

    So I cleaned the plugs and pulled the fuel pump fuse. Ran out of fuel pressure and stopped almost immediately but no momentary idle improvement.
    Put some fuel in the intake and re-started, kept it running this way for about 30 seconds. No noticeable difference, still stumbling and no difference in the idle, I did not expect it to run well but I did expect a difference.
    Only difference, the spark plugs now clean and dry.

    Another symptom could be the cause (or a rabbit trail). Will occasionally “spit” back through the intake, particularly if trying to start with some throttle. Compression test, all six cylinders about the same at about 150 psi. Sure hope it’s not valve timing but that should show up with the compression test right?
    Bore scope in the cylinders, hard to see much but nothing obviously amiss.

    So my best guess is the idle control valve went bad when I stopped at the second light.
    Anyone know if the rough idle, rough running and fouled spark plugs is symptomatic of a bad ICV?
    It’s an expensive part to replace without some idea if it is causing the problem.

    Any advice and experience is much appreciated. Thanks, John aka Kenneth

  2. #2
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    Sounds like a massive vacuum leak to me. Check the intake boots for splits and make sure all vacuum lines are hooked up. If the icv goes it should still be driveable, you would have a nasty idle surge but the car would be relatively normal off idle. My car acts like this if the charge pipes blow apart. I would take a look at that long rubber boot and see if its torn somewhere.

  3. #3
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    When was the last time the crank position sensors were changed? If the car can't time itself, it'll run like crap. I learned that the hard way when the timing mark fell off my flywheel and the car started shooting fireballs out the exhaust.

    Unmetered air shouldn't cause the car to run rich. A bad coolant temp sensor certainly would though, my car barely idled and ran like a poorly tuned cammed 350 chevy without the CTS hooked up.



    Have you tried running the car without the ICV hooked up? It should hunt between 600rpm-1500rpm which is where the DME will cut fuel and knock it back down.


    You can check this out for testing your ICV. If the ICV isn't buzzing though its either not getting power anymore or its shot.


    ICV Diagnosis
    NOTE: The diagnoses below don't all make sense unless you follow the steps in the sequence shown.
    1) Turn the ignition key to run position, but don't start the car. You should hear quiet buzzing sound from the ICV, and if you touch it with your fingers, a vibration. If not, either the ICV is bad or there is no control current.
    2) Start the car. Run the system "open loop" by pulling the electrical connector from the ICV. The RPM's should climb to about 1500-2000, and then oscillate back and forth between about 600-1500rpm. If reconnecting the electrical connector has no effect on RPM's, your ICM is probably at fault. (For the curious, your RPM's fluctuate because when the ICV is disconnected, the valve is stuck wide open, and the DME is the only thing controlling your idle. The RPM's rise until it cuts the fuel flow, which causes RPM's to dip. Then it restores fuel flow, and the cycle begins again.)
    3) Cut the motor. Pull the electrical connector from the ICV and connect an ohmmeter across the terminals. The reading should be about 9-10 ohms at temp 73+-9F(23+-5C). If you get an open circuit, it's time for a new ICV. If the resistance is much lower, you've got a short, and your ICM may be roached too, from the resultant excessive current draw.
    4) Disconnect the ICV hoses, and look into the outlet. Obtain jumpers and connect 12V across the ICV terminals. The valve should close tightly when voltage is applied, and open strongly when the voltage is removed. (Yes, it might look grungy and black in there, but resist the temptation to clean it w/ solvent for now - it could throw it out of whack!). If there is no movement or the movement is sluggish, your ICV is bad.
    5) Plug in the ICV electrical connector and turn on the ignition (engine not running!), all accessories turned off. Looking into the outlet again, the valve should be partly closed. If the valve is wide open and there is no vibration, you aren't getting any control current. To verify, unplug the ICV connector, and verify that you're getting voltage across it. If there's no voltage, your ICM is at fault.
    6) Reconnect the ICV hoses and electrical connector. Hook up an ammeter in series the ICV. W/ the engine fully warmed up and idling w/ all accessories turned off, the current should be between 400-500 mA. If the current is wrong, adjust the ICV current. Turn the adjusting screw until you get 460+-10 mA at 700+-50 rpm.
    KLUDGE: If you can't get the current in the proper range, just try to adjust the screw until your idle stabilizes at 700 RPM and ignore the current reading.
    If you can't adjust the control current properly, proceed to ICM Diagnosis. If the ICM checks out ok, then the ICV is probably out of whack. Maybe an ICV Kludge can help you peg the diagnosis (or fix the problem well enough for you to live with it).

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  4. #4
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    A massive amount of unmetered air wont cause a "rich" condition but if there is improper combustion to the extent that it sounds this car is experiencing the fuel wont burn out of the cylinders and you will have wet plugs. Especially if the car never gets warmed up because of its condition and is stuck in open loop operation. The wet plugs sound secondary. The backfiring through the intake is either poor timing, or a massive amout of unmetered air. If you pull the post afm boot off of any car and start it it will foul plugs and backfire through the intake and exhaust. It could be a cps like offroadkarter said, but icv will just cause a surge not backfiring and the car would drive mostly fine off idle.

  5. #5
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    New ICV did not solve the problem.

    Have not found vacuum leaks.
    All connections seem to be OK.

    Disconnecting ICV makes no difference.
    Disconnecting ECU temp sensor makes no difference.
    Disconnecting Thermo time switch makes no difference.
    Disconnecting oxygen sensor makes no difference.
    Disconnecting MAF stops the engine.
    4 – inside plugs may be a little blacker and wetter than #1 and #6
    Keep in mind I am running for several minutes at a time at idle but not at normal operating temperature. Also, keep in mind, this first occurred under normal driving conditions with engine at normal operating temperature.

    Clue! (although I don’t know what this means)

    While running, “MPG” gauge below speedometer which I think is actually a vacuum gauge swings steadily from minimum to maximum about every 5 seconds. Just like a slow moving pendulum.

    What does this mean?
    It must have something to do with my problem.

    Thanks for all the help, John Kenneth

  6. #6
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    What is your Fuel pressure read?

    You may want to rent a fuel pressure gauge and test it.

    When My fuel pump was plugged with rust the car acted very similar.

    My guess is fuel related. I'd bet your FPR or fuel pump is having an issue.

  7. #7
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    How's your dist cap and rotor?

  8. #8
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    I had this sort of problem years ago with my 83 733I. After replacing the Idle Control Valve and checking for all possible leaks I found it to be a Programa part called the Idle Control Unit or Module. I remember the dealer replacing this under warranty and the idle steadied right out. Part number on real OEM is 13411286134 Jeff
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
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  9. #9
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    I'm still trying to diagnose. ICVs (I have two now) both displaying same behavior. Resistance 9 ohms across the terminals.
    Both click when ignition is turned on. But neither "hum" or vibrate when ignition is on.
    Idle control Module above glove compartment on firewall is clean and connection clean and tight but It could be suspect. I am trying to locate one to change out.
    Could also be the signal to the ICM.

    Fluctuating MPG/vacuum gauge is telling me something. Must be the ICV is not controlling the idle and the ecu is trying to do so??

    Thanks for the help, sooner or later I'm going to find this.
    I also have a '91 735 so photos look familiar, when I get the 733 running again I start on the E32

  10. #10
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    If you're looking for a module, Programa is right here in Florida. This is their price for the unit. http://www.programainc.com/categorie...gory=4153&cl=1
    This is their home page. http://www.programainc.com/. I've dealt with them for years. They do everything on site and will repair your electronics or just do a swap. Good luck with this.
    Jeff
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
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  11. #11
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    Thumbs up

    Programma rebuilds have been total garbage as of late. You should just open it yourself and repair it.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
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    Ford, MB, and GM round out the pack.



  12. #12
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    I never had to return a thing to Programa. One of their best bench man is gone since last year, but even since then I've seen a few cluster boards, Swords and other electronics. Never a problem. Not sure if you have anyone like them in Texas, but their shop in Boca Raton really has some smart people. Vista BMW (largest BMW dealer in the world) uses them all the time for repairs. I wish I knew what problems you had with them.............and with who. I guarantee you my buddy who works at Vista for 33 years can make things right for you. PM me if you'd like me to help get a problem fixed.
    Jeff
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
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  13. #13
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    I hadn’t thought of trying to repair the idle control module. I repaired the Light control module on the E32, just carefully tried to re-solder everything I could see and to my surprise it worked so I will try it on the E23. Thanks, John Kenneth

  14. #14
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    Once you disconnect it to make any repairs or if you find a problem that causes you to find a replacement I wouldn't be surprised once the fixed or new one is in, you have an idle problem totally different for a few minutes. Sort of when I replaced my little fuel regulator. The one with the vacuum hose coming off of the top. Mine had failed and when a new OEM regulator was installed on first start the engine was whacky. My BMW guy laughed and said just take it for a ride.......just the way it is and come back. Do 1/4 of a mile. I did and when the 1/4 mile was over the engine had settled down to such a steady idle it sounded like a sewing machine. Evidently (at least I learned that day) these cars have an engine management system that takes it's time to recognize new parts. I'm thinking that it would act the same with a change in the module. I could be wrong, but you've got me thinking about my 733. Eight years and the two biggest problems were Alternator Bushings that kept bending and having to be replaced.....something redesigned on the E32, and sunroof drain leaks leaving me water on the floor. Once I drove it to Metric Mechanic in KC and had them swap my transmission with bad syncro in 2nd and 3rd to their upgraded Getrag with their short throw shift kit. What a great drive back to South Florida breaking the traney in.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
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  15. #15
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    Idle control valve

    I have a 1982 733i. There are many issues that could cause rough idle problems. If you want to deal with items that deal directly with idle issues, then start with the idle control module and the idle control valve. The fact that when you unplug the icv there is no change in idle doesn't mean the icv is bad. Check to see if there is power going to the plug with a light tester. If there is no power going to the plug, you have a bad idle control module. Your icv could still be bad, but you need a good control module to proceed. If you do have power going to the icv, then yes, the icv is probably bad. But when you unplug the icv the car should race up and down.

    If you are going to keep the car, I recommend you purchase a new idle control module. Programa is junk!
    Don't waste your money. You can buy new for $300 vs $100 from programa. I have so many programa parts that don't work it makes me sick. If you do find the icm is bad and you buy a new one. Disconnect the negative cable before you plug it in. These are very sensitive electrical components.


    If all that checks out, you need to to a compression test and a leak down test.

  16. #16
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    Quote Originally Posted by CroughtonE32 View Post
    I had this sort of problem years ago with my 83 733I. After replacing the Idle Control Valve and checking for all possible leaks I found it to be a Programa part called the Idle Control Unit or Module. I remember the dealer replacing this under warranty and the idle steadied right out. Part number on real OEM is 13411286134 Jeff
    Just curious, how did you get a dealer to replace something under warranty that is on a 30 year old car? Must be a hell of a maintenance plan lol

  17. #17
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    Quote Originally Posted by GTBrandon View Post
    Just curious, how did you get a dealer to replace something under warranty that is on a 30 year old car? Must be a hell of a maintenance plan lol
    He had it back in the mid-80's.

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