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New BMW Owner

Discussion in 'E31 (1991-1997)' started by phoenixop, Apr 11, 2015.

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    phoenixop

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    I guess this is the intro everyone talks about. New to BMWs, not new to cars. Street raced in L.A. in the 60's ran a '58 Vette gasser. Punched 327, dual 750cfm Holley double pumpers. Also ran 426 wedge and Hemi's in a '62 Dodge. Graduated? to mini's (original). Owned a fleet at one time (8). Moved on to real life, kids, wive's, girlfriends etc. Now retired and bought 2 projects. First is a 1967 Buick Riviera, double black, slammed, cruiser and... wait for it... 1991 BMW 850i. Wanted one of these things for about 15 years, just got the time to deal with it. The one I bought, I saved from a bad home. 166k miles, has issues, sunroof, ABS, seat adjust, driveshaft, typical from what i've read, but I only paid $3k for it. Runs and drives beautifully, when it's not in a bad mood. That's pretty much the gory details. Glad to see there is a lot of knowledge here. Definitly going to need it with the BOAT (850), you know, Break Out Another Thousand!
    See ya
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    MGarrison

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    Welcome to the club & forums! Yes, BMW's, besides their anachronisms, has its acronyms - Break My Wallet... Bring Money Withya...

    You'll no doubt decide on your own priorities, but if it were me - if the sunroof is closed & not leaking, I'd say leave it that way & never open it, at least certainly not until ready to tackle that project, and I'd make it one of the last, barring leak elimination which might be a fairly immediate priority. If the driveshaft is the typical guibo disc & center-support bearing, I'd get that out of the way, unless it's a manual & clutch replacement is soon part of the picture, as the driveshaft has to come out for a clutch job anyway. The seat, again, if it's in an acceptable position, perhaps leave it there until later. The ABS, I'd try to take a methodical approach to diagnosing that & just drive carefully in the meantime, you obviously grew up without it & I'm sure can manage fine in the meantime.
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    charlson89

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    Welcome to the club nice rides!
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    phoenixop

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    Thanks for the hello. Love the acronyms. It's an auto, the sunroof doesn't leak (Miracle), seat position is bearable, driveshaft is TOAST, probably no bearings left. The biggie is the fuel leak. I knew it was leaking, thought it was a hose, no big deal, but then I saw it literally running down the end of the header, but only when the engine is running. I couldn't get contorted around to see exactly where it was coming from (jack stand boogie), so I broke down and took it to (gasp) the dealer. The service writer and I are starting to get on a first name basis. Threw it up on the lift, couldn't make the d#!n thing even drip. Tried cooling it down and started it up, nothing. Gave up, drove home, it leaked like a sieve, I can watch the gas gauge go down. It's like driving my old vette again (4mpg). If these things have any known fuel Achilles heel somewhere around the back of the engine, that would be helpful. Besides all it's issues, I got a real reality check when I called Brett Hurless who, I believe is listed as a technical service advisor for the club, after telling him I owned an 850 and I quote, "I hate 'em with a purple passion! I won't even work on them". We'll hey, thank you Brett. You've been a great help. And so it goes... Ah the good old days when you could see the ground around the engine through the headers.
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    MGarrison

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    Ah! Well - there are other TSA's, including Charlson here - you might try some of the others. The 5.0l v-12 stuffed into the E31 engine bay doesn't leave much extra room. They don't make a Bentley manual specifically for your model, but whatever engine section that covers the v-12 in this one might be useful. http://www.bentleypublishers.com/bm...bmw-7-series-e32-1988-1994-repair-manual.html

    Haven't had that manual in hand, so I can't tell ya how detailed it gets for the engine section.

    Realoem.com might be helpful to give you an idea of how things run - given the age at this point, if it's the original fuel lines, it might be advisable to replace all the rubber fuel lines in the engine bay, and the fuel pressure regulators.

    http://realoem.com/bmw/showparts.do?model=EG23&mospid=47335&btnr=13_0603&hg=13&fg=15

    If you do your own work, use Roundel advertisers & google to comparison shop for parts - some things may be dealer only, if your dealer doesn't offer a club-member parts discount, there are dealers that advertise in the Roundel also.

    If you look at Bavarian Autosport (Bavauto.com), usually if something there is listed as special order, that means it's only available from a BMW dealer.

    The driveshaft u-joints could be bad, but if the center support bearing is shot, that can have the driveshaft clunking and sounding pretty bad - (parts 1 & 2): http://realoem.com/bmw/showparts.do?model=EG23&mospid=47335&btnr=26_0254&hg=26&fg=10

    That diagram doesn't show a typical BMW driveshaft flex disc (aka guibo), the driveshaft's joining to the transmission may be different since it's an automatic. In a manual, a disintegrated guibo is also a potential noise source. Check those possibilities out before going for a replacment driveshaft.
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    phoenixop

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    What a relief! No 850 haters. Maybe some complaining, but I'm sure I will do my share also. Thanks for the warm welcome. I have a factory BMW Repair Manual Edition 5/90. Little earlier than the car, (production date 2/91), but everything looks right. I also have a 1991 BMW 850i Electrical Troubleshooting Manual. In it I find a butt-load of wiring diagrams, but not so much troubleshooting. I'm used to decision trees, and I'm not finding those in it. As for the driveshaft, I took the car to a Commercial Tire and really lucked out. The main mechanic owns and loves BMW's. Threw it up on the lift, told me which pieces I needed to get for the front and rear suspension, taught me about centric rings to cure my Shimmy and told me where to send the driveshaft as he was twisting it back and forth 3 inches in ALL directions and told me the driveshaft was so bad it was a safety issue, which I figured out on my own based on how much slop there was. Did I mention, he didn't charge me anything? The driveshaft is my first priority due to the pole vault effect. Saw a couple of guys do that when I was street racing. Always a treat! previous owner shot expanding foam behind the glass inside the passenger rear view mirror. Really? Don't know what he was trying to fix, but it made that mirror unadjustable. So I guess before I can attempt to diagnose it's real problem I have to remove all the STUPIDITY he shot in there. This is what I meant by saving this car from a bad home... I wish I could hate the thing, but then I look at it and it's just sooo sexy I can't. 23 years later and it's still hot looking even compared to current vehicles. I made the mistake of checking out the fuel plumbing diagram on RealOEM. Holy crap what a mess. It looks really simplified in the diagram until you remember you have to disassemble half the car to get to that stuff. Can I use generic plain wrap fuel line or must I use high $ BMW blessed stuff? Speaking of fuel, at one point (pre-fuel leak), I was getting 15 mpg. From I've been reading these things like to get down and boogie. Are they civilized enough that you don't have to do that or should I plan banzai runs on a regular basis? So many questions, so little time. Thank you gentlemen
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    charlson89

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    The 850 is the one vehicle I can never look away from it is timeless and runs amazing. But of course takes quite a bit of money to keep it going. The vehicle electrically was years ahead of its time. For instance your engine was the first one to use electronic throttles. Congrats on getting the repair and electrical manuals those will help quite a bit. The M70 engine is smooth running that sometimes you can't even tell the car is running and yes they do actually move when you get into them. Always good to open it up ever once in awhile to clean the engine out. The fuel line for that engine may have special connectors that need crimping on the fuel line. Not like the older muscle cars where you can just use plain fuel line.
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    phoenixop

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    I've noticed, even though you don't own an 850 if I'm reading your info correctly, you most certainly know a lot about them. Really going to pick your brain. It's kind of weird for me coming from the land of huge v8's, that my v12 is only 2 cubic inches bigger than a Boss 302 Mustang. Soda can cylinders.
    Oh here's question that's been bugging me since I stuffed electronic ignition into the Riviera. Does anyone, (Charlson) know if the distributors on '91 850's are Bosch and if so is there a Bosch number or any number on the body of the distributors? I had a long conversation with Pertronix. They make an electronic ignition that fits inside the stock distributor and it senses the lobe to fire the plugs. I asked about the 850 and they said they've done lots of Bosch ignitions, but the don't have information on car models. That is what I installed in the Riviera. No more points, added a super high voltage coil and E3 plugs and it runs really great. If I can get the Bosch number, and Pertronix has developed an electronic ignition to fit it, it's possible there may be a way to do the same for the 850. The ignition unit doesn't care if there 8 or 12 cylinders, it just fires when the lobe passes. The cap and rotor direct traffic. It's more a matter of mounting it to the plates.
    Any info would be helpful.
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    MGarrison

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    Never done any electronic ignition conversion - but - for stuff like that, you can look up part numbers on realoem & then google BMW & the part number, or search the part number on sites like Pelicanparts.com or autohausaz.com -

    Going the google route came up with this -

    http://www.eeuroparts.com/Parts/10968/Distributor-Cap-03195/

    E31's (like the M20 in my E30) are Motronic (DME) ignition systems - from my E30 Bentley manual:

    "Cars with a 6-cyl. engine (obviously yours is a 12, though the V-12 design of that era is basically two banked M20's in a single block) have a Motronic ignition system. In Motronic systems, also known as Digital Motor Electronics (DME), all ignition functions & fuel injection control functions are controlled by a single electronic control unit (ECU). Ignition timing is based on inputs the ECU receives for engine load, engine speed, ignition quality, coolant temperature, & intake air temperature. The only function that the distributor serves is to distribute the high voltage to the individual spark plugs. The distributor is an integral part of the cylinder head and there is no mechanical spark advance system"

    The E31 might have more inputs, but I'm reasonably sure it can't be much different than the other straight-6's used then.

    Part 12 (rotor) here: http://realoem.com/bmw/showparts.do?model=EG23&mospid=47335&btnr=12_1658&hg=12&fg=05

    attaches to the camshaft(s) via part 4 here: http://realoem.com/bmw/showparts.do?model=EG23&mospid=47335&btnr=11_1091&hg=11&fg=25

    Hard to guess why someone might shoot foam behind the mirror, but if you find that the reason was to fix the mirror into a set position because the motor or whatever was inoperable/broken/etc. ebay is one option - search ebay for BMW E31 mirror - I found some listed, a couple of pairs, and some either side individually - might be the easiest way to put a working mirror back in place for the least expense.

    BMW's typically originally use German crimp-on hose clamps. Those end up too destroyed to be re-used, I would think in many instances German screw-on hose clamps can be used instead, unless space or specific reasons dictate otherwise. Bavauto & probably some others should have the special crimping tool if you needed/wanted to use o.e. style crimp-on hose clamps. I recall reading something that German hose clamps are designed to help keep hoses from getting pinched.

    BMW engines do better if run through their rev ranges more often than not (fully warmed up, of course). Toodling around at low revs or majority stop & go driving, especially if it doesn't get fully up to temp before shutting off, tends to increase buildup of internal deposits more. That doesn't mean you need to redline it each time you take off from a stop light, but - BMW engines can run all day long on the autobahn, so you get the idea. You don't have to go nuts, but don't be afraid to run it (within sane bounds of safety for street & highway conditions, that is!).

    No idea of similarities, but the diagrams might be useful - the link in the post is to a .pdf of a warranty procedure for 7-series V-12's predating yours, perhaps there are fuel line routing & access similarities, such as removing fender liners for access, etc.

    http://www.bimmernut.com/forum/show...-pressure-hose-replacement-E32-750-V12-engine
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    phoenixop

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    Since I haven't opened up the distributors, I assumed they have a set of points enclosed inside those formidable caps. I may be under a false impression.
    Your description sounds like a modern day computer, not something created only 2-3 years after the IBM PC. So there are no points, mechanical advance plates, springs or condensers inside those things? If that's the case, then these things are advanced for their time. Of course this begs the question. Why are tube-ups so frigging expensive? Is it just because there are 12 of everything? It seems like you have to change wires at every service
    I have RO's from prior owner showing wires and plugs at every tune up or service. Is there something inherently weak about the plug wires or are they just hard on them.

    The mirror issue. Somewhere I read on some 850 forum, blog or whatever, that if the memory, or motor freaks out the mirror will jiggle or move in some bazaar fashion. I hope that's not what prev-own was trying to fix. I tracked down a used, black mirror which matches my car with a 6 month guarantee. Probably paid too much, $175.00, but seeing how expensive a new one was, it seemed like a bargain.

    We'll I'm off to fix the 6 way power bench seat in the buick. Like the BMW it only goes so far and like the BMW it uses flex cables. Oh boy. Guess I'll make my bones on the buick. Luckily I have a cherry picker that can substitute as a seat removal tool in both cars.
    Thanks again for all the insight and tech. Assistance.
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    phoenixop

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    Since I haven't opened up the distributors, I assumed they have a set of points enclosed inside those formidable caps. I may be under a false impression.
    Your description sounds like a modern day computer, not something created only 2-3 years after the IBM PC. So there are no points, mechanical advance plates, springs or condensers inside those things? If that's the case, then these things are advanced for their time. Of course this begs the question. Why are tube-ups so frigging expensive? Is it just because there are 12 of everything? It seems like you have to change wires at every service
    I have RO's from prior owner showing wires and plugs at every tune up or service. Is there something inherently weak about the plug wires or are they just hard on them.

    The mirror issue. Somewhere I read on some 850 forum, blog or whatever, that if the memory, or motor freaks out the mirror will jiggle or move in some bazaar fashion. I hope that's not what prev-own was trying to fix. I tracked down a used, black mirror which matches my car with a 6 month guarantee. Probably paid too much, $175.00, but seeing how expensive a new one was, it seemed like a bargain.

    We'll I'm off to fix the 6 way power bench seat in the buick. Like the BMW it only goes so far and like the BMW it uses flex cables. Oh boy. Guess I'll make my bones on the buick. Luckily I have a cherry picker that can substitute as a seat removal tool in both cars.
    Thanks again for all the insight and tech. Assistance.
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    phoenixop

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    One more question. How do I get a picture on the little gizmo that shows me as a question mark. I've wandered around and can't find anyplace to upload one, or put a list of cars.
    Thanks ahead...
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    MGarrison

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    Scroll up, in the dark blue bar that has "Forums - Members - Help" on the left and your "Username - Inbox - Alerts" on the right, move your mouse pointer over your username and a menu should pop up, and towards the lower left on that you'll see "Signature" & "Avatar" - click "Avatar" to change your avatar pic from the default question mark, and "Signature" if you want to add something to appear as your signature after each post. I kept my signature short so as to minimize page scrolling through threads, although it is possible to set preferences to not show signatures.

    If you look at the 2nd picture of the inside of the distributor cap in the eeuroparts link above, you can see what it looks like - the ignition coil input goes to the middle contact; the metal contact on the end of the rotor (part 12 in the realoem.com link above) completes the circuit, and the voltage passes through each outer contact to the plug wires and spark plugs. No electronics or anything else in the distributor cap, it's basically a brass-alloy conduit insulated in the plastic of the molded cap. The metal contact points of the rotor & distributor cap wear, requiring periodic replacement. I forget the exact size, but the rotor securing screws need a small-ish metric hex-wrench for removal and installation.

    Here's a basic diagram of the 6-cyl setup that might help visualize - yours might be this x2.

    BMW E30 6-cyl ignition diagram 1.JPG

    Charlson might have a comment about the durability of the spark plug wires - by the late 80's, BMW was using computer algorithms to suggest maintenance intervals - replacing plugs, checking the plug wires, distributor cap, and rotor (replacing as needed) , would be an "Inspection II" item - prior to electronically monitored & determined service intervals, Inspection I & II items to be checked/serviced was at specific mileages. I think Inspection II was something like every 30k miles, although maybe it was more. It's possible that tight packaging meant more heat underhood, shortening the durability & lifespan of the the plug wires, but that's just speculating.

    Some basic info on your engine:

    http://en.wikipedia.org/wiki/BMW_M70

    Some info on Bosch Motronic (not sure which version yours has):

    http://en.wikipedia.org/wiki/Motronic

    By the end of the 80's, I'm reasonably sure all BMW cars were using Motronic engine control systems. I _think_ the "eta" baby-six motors of the U.S. 325e models (came to the U.S. in '85) that were produced to 1988 may have been using a simpler version of Motronic ECU's, but the 325i models were using more advanced Motronic 1.1 & then 1.3. Since the M70 uses MAF's instead of AFM's (air flow meters), its motronic would have had to utilize inputs from the Mass Air Flow sensors. The last of BMW's in the U.S. that would have had a more conventional transistorized coil ignition system I think might have been the '84-only 4-cyl. E30-chassis 318i.
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    phoenixop

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    Wow, I just got a crash course on the M70. I read that the motronic unit controls the idle. Here's what happens when the car is in a bad mood. After start but before it hits running temperature, the idle will vary between approx. 750 and 1500 rpm, cycling every 2 seconds. If you try to drive it it's like the worst surge on the planet. If you shut it down then re-start it settles down and idles and runs normally. Of course every once in a while, it gets its bad mood on again and starts cycling again. Could this be the motronic unit or as another BMW guy suggested, use some mass air flow sensor cleaner. Any thoughts, ideas, voodoo or magic spells would be appreciated.

    Thanks for the diagram of the distributor etc. Looks really simple until you realize there is yet another black box running the show.

    Also, thanks for the avatar tip. Appreciate the help.
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    MGarrison

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    Always glad to be of help, of course I always wish I knew more to help more too! Charlson hopefully has some better ideas than me, but spraying the sensor wires (carefully) with some MAF cleaner is something to try. Vacuum leaks could be an issue, there's a whole slew of possibilities there - I don't know how your engine manages idle control; I couldn't find an idle control valve listed in realoem.com or searching Bavauto.com; with the MAF's, it may be that the ecu takes in various inputs and handles idle control. If your manuals have ecu pinouts, that might give you an idea on how it works.

    You can kinda get carried away with internet sources, so getting the best advice on exactly what to try before launching in, especially with buying parts, is always a good idea - that being said, a few interesting finds -

    Seems like the guy in the 2nd post of this thread, although for 7's, might have insight about M70's -

    http://www.bimmerforums.com/forum/showthread.php?1881706-Help-with-M70-750iL-vacuum-leak-rough-idle

    Other stuff -

    http://twrite.org/shogunnew/diagnosis/engine.html

    Apparently M70's that pre-date yours had less-than-optimal pcv valves, but these might be something to put on a checklist, presumably the later ones will eventually require checking/replacement too - http://bmwe32.masscom.net/sean750/vcv_replacement/VCVvalves.htm

    http://www.bimmerforums.com/forum/showthread.php?1363460-M70-idle-problems

    A gasket vacuum-leak issue on a later v-12 -
    http://atlanticmotorcar.com/tech-tip-bmw-v12-engine-vacuum-leakage-correction-cold-running-2/

    Ok, some speculation on function - My E30 engine uses an idle control valve & a cable direct from the gas pedal to the throttle body (controlling the throttle butterfly) - apparently yours is drive by wire, and seemingly doesn't use idle control valves - looking at the realoem.com diagram for your throttle bodies (http://realoem.com/bmw/showparts.do?model=EG23&mospid=47335&btnr=13_1423&hg=13&fg=15), I'm guessing the cylinder shape off to the left is the control motor for the throttle butterfly - if the M70 presumably needs some minimal air for idling, (which is done by the idle control valve on E30's, 8th full paragraph here - http://www.pelicanparts.com/bmw/techarticles/JF-Tech/BMW_E30_3_Series_Idle_speed_troubleshooting.htm), it has to get that air somehow - I wonder if with the dive-by-wire, the ecu just tweaks open the throttle butterflies enough for that, forgoing the icv's that were common to the other BMW engines then, on the presumption the motors could be very precisely controlled - hmm. Or, some butterfly bypass maybe routed thru the throttle body? Anyway, that's the kind of question for someone who knows better how idle control works on M70's.

    I had something wrong with the idle-control circuitry internal to my E30 ecu one time, the problem was a bad idle surge that, after replacing the idle control valve & testing everything else & replacing anything else related, only went away when I swapped in a different ecu. Can't speak for M70's, but I think my issue in that instance, problems within the ecu, is not common, and for E30's, about the last thing anyone's likely to suspect. Drove the neighbors crazy with the 800-1800 rpm revving though until I finally got it resolved (made street driving a pain too!).
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    charlson89

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    The rough idle I would start by of course looking for any intake leaks. The best way to do this is use a smoke/ vapor machine but most people don't have access to those. So the other method is to use brake clean and spray all the intake areas and vacuum hoses and listen for the engine to rev up if it does then you found a leak that needs to be fixed. The best way to check the mass airflow while the vehicle is doing the rev up and down unplug them and see if the idle smooths out. This of course can set a check engine light and if you don't have a tool to clear it then it will remain on. If it does smooth out something in the sensor circuit is causing the issue not something mechanical. Most likely the MAF since BMW did have issues with the early ones. But of course it still could be the motronic as well since it take the MAF readings into account for fuel and spark adjustments.
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    phoenixop

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    My first instinct is to try the "cheap fix" just to clear out all the old junk. The only things I know are that the tranny was just rebuilt last year (April '14). Don't know if it was done correctly. It was done by Clinton Transmission in Clinton Maryland, where I picked up the car. The bill was $2200.00. Apparently, they rebuilt the tranny and replaced the torque convertor. Somebody removed the cats, so it has straight pipes back to the rear mufflers and no o2 sensors. My preference would be headers and no mufflers, but I have to deal with emissions testing and even though I live on 5 acres, my neighbors probably would not be very happy when I'm going up the street like a bat out a hell with open pipes. Fun though...

    Since I have no idea what else may or may not have been done to it, I'm gonna cheat and try the "cheap fix". Of course, that will have to wait til I get the driveshaft sent our for rebuild/balance. The thing as it is, is a destruction derby on wheels.

    Is it my imagination or are issues with these cars the result of several different causes? It's almost overwhelming, the sheer technical info one has to absorb to work on them. I've always heard that about BMW's and Benzes, but I thought, "you know what, it's just a car. Yeah a car with a butt load of more gizmos, but just a car nevertheless. Air and fuel go in and work comes out." That's what I thought til I bought one.

    One other thing. Some former rocket scientist put standard shocks/struts in and removed the EDS system. The cables are still there, but no connection or any way to connect to the existing shocks/struts. Another thing on my list.

    My hope is to someday have everything working that came on the car. I apparently need to replace the crash module because I have the random blinking flashers everytime you move the car, bump the car or look at the car. Cheesh!

    Can't tell you guys how helpful you've been. If I didn't love the car so much, I could get depressed about the sheer volume of work and money it's gonna take to resurrect her.

    Buick/BMW seat update. Yup. Cable on the buick. Took the remaining broken piece, threw it into a drill and synced all the operators, so now all I need to do is find a cable and screw it on. Got a line on one. You can tell it's an old Buick. NOS cable $27.00 not $270.00.

    Thank you again, gentlemen.
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    wbmunroe

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    Congrats on the purchase, welcome to the forum! I too just acquired a '93. Fortunately, I was able to find one with documentation of work performed dating all the way back to the original owner (I am owner #5). It's a magnificent automobile, and the guys in here have been helping for quite some time! Where did you find the electrical information? That is something I would certainly like to have on the shelf!
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    phoenixop

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    You can download it for free. http://bmwelectrical.blogspot.com/2014/04/electrical-troubleshooting-and.html?m=1

    I'm a paper kind of guy, so I printed it landscape, spiral bound it. It's pretty useful. I would like to find a true troubleshooting manual with decision trees, but no luck so far.

    Looks like you have prior experience with BMW's. This is my first BMW ever. I'm an old street racer, but I have been a parts Manger at several dealerships in L.A. in the 70's. Dodge, Fiat, Lancia, Renault and Mazda. This thing is kind of intimidating, but I want to bring it back to life.

    Thanks for the welcome and glad to meet another 8 owner.
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    MGarrison

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    No doubt, check the easy stuff first, like Charlson sez, if you can confirm any vacuum or intake leaks then you know what to address. I don't know that I've ever seen decision-tree setups for BMW diagnosing, my Bentley manual, (somewhat inconsistently) for various things lists symptoms & possible causes.

    Diagnosis I've always found is the hard part, removing & replacing things, less so - that's why help from someone with specific BMW experience like Charlson here is so, uh, helpful! Various symptoms (depending of course on what it is) can be both - from a single cause, or sometimes, multiple causes. For instance, it would be possible to have vacuum leaks for your idle issue from one line/gasket/etc., or several. But, vacuum/intake leaks aren't the only possibility for idle surging, but, one of the most common/likely, thus why it's a good place to start.

    Scrapping the EDS/EDC I suspect might be fairly common - not sure what all the issues might be, although I think I recall reading about leaking seals & what-not. It's not much of a stretch for anyone looking at repair/replacement costs & seeing that 4 new shocks &/or conventional springs can be done for less, maybe a lot less, than fixing the o.e. system, & would go that route. I wouldn't know the specifics on how the system works, but I'm guessing the goal was to try to give increased ride-quality comfort when desired, and the option to stiffen the shocks for improved handling when desired. The question might be how optimally the EDS achieves both, or either, when it comes to deciding whether it's worth putting back.

    If you're going to need it to pass emissions, I'm not sure how well it will be able to do that without cats and working 02 sensors. I'd say try first, but don't be surprised if it fails. The ECU uses the feedback from the O2 measurements to determine how the engine's running, and that, plus other inputs, determines which fuel maps are used for fuel delivery, to give optimal running, fuel economy, & emissions. With no 02 sensors, you're likely getting a permanent check-engine light, and since the ECU isn't getting that input, besides your fuel leak blowing gas mileage, it would have less-than-optimal gas mileage because it would be running off some default fuel setting. If you ultimately have to re-fit cats, shop around, I _think_ there may be some cat options somewhat more affordable than o.e.

    Can't tell ya anything about the crash module or cause for blinking lights, have to ask Charlson that one.

    Not sure what issues you might be having with the seats, don't know their construction - there are surely a variety of motors, buttons, controls, & cables (not sure if there were in-seat airbags that early, I kinda doubt it). One issue common to the E34 5-series of that era was the seatback tending to twist one way or another, which I think was a cable issue, maybe stretched (you can find more on that googling if you want). Guessing, but the 850 seat bottom may move fore/aft via a motor(s) and screw shaft(s), probably hard to see much with the seat in the car.

    Years ago when it was still my daily, the exhaust system fell off the E30 - had some very unhappy neighbors there for a bit driving around with headers-only until I got things fixed back up!

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