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TriggsyOffline
Post subject: M70 V12 intermittently stalling in my Diablo  PostPosted: Sep 21, 2015 - 09:34 PM
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Hi all, i hope you can help.

I now have my Diablo up and running using the originals ECU from a 1989 750 (M70). The engines runs well and pulls very well too but i have an issue where it intermittently stalls when i stop at junctions. When i come off the revs you can see the revs drop to about 400 rpm and which point it may or may not recover.

I've was wondering if a lack of a speed sensor could be an issue but i get maximum revs and power so i don't think it's that (i've ground the wire anyway but it made do difference).

Anyone got any ideas please?

Thanks
Simon
 
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lambo1Offline
Post subject:   PostPosted: Sep 23, 2015 - 11:52 AM
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hi Triggsy, I sounds to me like you may have a leaky intake gasket its very common , it goes lean after coming off throttle I would suspect the intake gasket.
Have you rebuilt your dk motors, I recently rebuilt mine and in the process discovered something I have not seen on any forum about these Dk motors ,on the throttle bodies they have two unused vacuum tubes coming off each throttle body each had a rubber cap covering the unused vacuum lines all four of them had cracks in the side of these rubber bungs I would check these first as they get very hot in there location, you will have to remove the dk to check them the rubber was so hard and cracked I had to cut it off with a knife. and if that is not the cause I would go for the intake gasket but the dk resolve is way easier and if that don't fix it try asking on this site heaps of info and even fault trees created by shogun
http://www.bimmerforums.com/forum/archive/index.php/f-7.html
 
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TriggsyOffline
Post subject:   PostPosted: Sep 23, 2015 - 02:17 PM
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Hi Lambo1, thanks for the reply.

I'm glad you have menioned the air leak as i was thinking along the lines of a vacuum issue somewhere and a leaky air intake would make sense. I have already stripped the DK motors and cleaned them, i've also replaced the rubber bungs as you mention so i should be ok on that front. I'm also going to clean the MAF sensor just to be sure but i like the idea of a leaky intake gasket so i'll strip down the manifolds and seal them up with Hylomar.

Thanks again for your help, i'll post up on here how it goes.

Simon
 
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AdrianBurtonOffline
Post subject:   PostPosted: Sep 23, 2015 - 11:57 PM
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While it is running spray brake cleaner on the places where you suspect a leak, if your engine RPM changes you have found your leak

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TriggsyOffline
Post subject:   PostPosted: Sep 25, 2015 - 10:24 PM
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I removed the manifolds before seeing the comment about spraying brake cleaner but what i have found around 2 inlet ports is golden brown stains on my previous nicely painted head. I think this proves there is a leak so i'll put it all back together with some Hylomar over the weekend.

Thanks
Simon
 
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TriggsyOffline
Post subject:   PostPosted: Sep 30, 2015 - 07:14 PM
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Hi guys,

I've just got back from a test drive following my air intake fix and a clean of the maf sensors. While it didn't stall the revs still dropped low before recovering so i don't think i've fixed it. I had a similar thing a couple of weeks ago when an evening drive in the cold air was a lot better than a drive in the warm air the next day.

What i have also noticed is the awful smell of exhaust fumes, i literally stink of fumes by just being near the car. I'm now wondering if i'm running rich, i don't have lambda sensors fitted as they weren't on the 750 car that i took the engine and loom from.

Anyone got anymore ideas for the stalling and bad smell, or could they be related to the same cause?

Thanks
Simon
 
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AdrianBurtonOffline
Post subject:   PostPosted: Oct 01, 2015 - 11:28 AM
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I think not having the O2 sensors in is a big part of the problem, the computers have no idea what is going on. Have you tried disconnecting the battery to reset the CPU's

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TriggsyOffline
Post subject:   PostPosted: Oct 01, 2015 - 08:04 PM
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The battery had been disconnected many times over the last few months for various reasons and hasn't really made a difference. However, i haven't done it in the last 2 weeks so i'll give it ago.

The lack of o2 sensors issue could well be issue. I'm 99.9% certain they weren't fitted to the donor car but that was so long ago i can't be 100% sure. I'm thinking of getting a diagnostic reading done and hoping it will show up lambda sensor errors. At least that way i know the sensors will be recognised if i fit them.

Thanks
Simon
 
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lambo1Offline
Post subject:   PostPosted: Oct 02, 2015 - 02:25 AM
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Triggsy wrote:
The battery had been disconnected many times over the last few months for various reasons and hasn't really made a difference. However, i haven't done it in the last 2 weeks so i'll give it ago.

The lack of o2 sensors issue could well be issue. I'm 99.9% certain they weren't fitted to the donor car but that was so long ago i can't be 100% sure. I'm thinking of getting a diagnostic reading done and hoping it will show up lambda sensor errors. At least that way i know the sensors will be recognised if i fit them.

Thanks
Simon


Hi Simon I have a e32 for a donor its an 88 English car and it has no o2 sensors from factory, I have just rebuilt the DK as I said a couple of weeks ago and read up that this procedure is a must do or it will run very rich

BMW 750 DK SYNC

Put the car in first gear (1) and accelerate to 5,000 RPM, release the throttle and let the car roll to almost a complete stop (do NOT use the brakes to slow it down), when it has almost completely stopped, press on the gas until you hit 5,000 rpm's again. Repeat this 3 times, put the car in PARK and let idle for a few minutes. Turn off the car - You have now synched the DK motors.

I have also heard that the 750 m70 has multiple water temp senders that send 1 signal to the dash gauge and a signal to each of the cars ecu these are known to fail also and cause either very rich or limp home mode they are on the water bridge at the rear of the motor. All the diagnostics are built into the car and display on the fuel computer section ,have you done the STOMP TEST most of this info is up on Bimmerforums.com or this is an excellent site http://twrite.org/shogunnew/topmenu.html

Regards
Graeme
 
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TriggsyOffline
Post subject:   PostPosted: Oct 02, 2015 - 08:27 AM
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Hi Graeme,

I cross posted this issue on the Bimmerforums and Shogun has given me some advice about the tranmission wires from the ECU too. I have tested the coolant sensors and they are fine but that was at the sensor end, what i will do tonight is check at the ECU end in case of a break in the wires.

I tried the stomp test but i understand it doesn't work on the UK cars so nothing happened. I have also synch the DK motors but i will try that again now that everything is cleaned up.

Can i assume your car is running fine and you don't get any strong smells? It would be nice to know it can run fine if set up ok.

Thanks
simon
 
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lambo1Offline
Post subject:   PostPosted: Oct 02, 2015 - 11:11 PM
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Hi Simon, my donor was not in a good state, the fuel tank is extremely rusty and with old fuel in the tank it seems to kill pumps the filters seem to work on the pumps so the rubbish does not appear to get into them but the fuel smells real bad and then the pumps die, my engine does not run at present I have just replaced the 2 sump gaskets that where leaking badly , allowing air into the sump, the sump on these must be negative pressure, if air gets in then the oil is sucked up through the pcv valves and right through the engine , so I had lots of oil smoke so much the car disappeared lol, I was told by an old bmw tech the sump gasket is the cause, both of them are a mission to change without removing exhaust or gearbox but I found a way to do it without removing the gearbox or exhaust, my car is like yours running very rich, and sometimes only one side runs,i found lots of dry joints inside the ecus where they connect to the huge multi plug on them nearly every joint was bad its an 1988 and all the solder had crystallized so I removed the old solder with a solder remover, and iron and redid the lot, it does not take long, about 3hrs now if I bang the ecu the car continues to run on 12 I would suspect your wiring from the temp sensors is dry at the ecu, can you give any info on the autotrans wires you mention. I cant remember if the stomp test worked on my car I think it did, I will see if I can find out for you once I get the plugs back in etc. Are you using the oem dash cluster because it has an id chip in the 1988 model that is plugged in the rear of the cluster that tells the ecu if its a v12 fuel tank size and all sorts of other stuff, if yours is a later model that info is stored in the light control module ie e38 and above
 
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TriggsyOffline
Post subject:   PostPosted: Oct 03, 2015 - 10:16 AM
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Hi Graeme,

Here's a link to my post on Bimmerforums where it details the transmission fix i mention.

http://www.bimmerforums.com/forum/forumdisplay.php?299-1988-1994-(E32) (for some reason it's not including the E32 in the link. Just click on the link and you'll see my post part way down).

I replaced all the gaskets and oil seals on my engine so it appears to be oil tonight.

I will check the solder joints though, makes sense while i have access to the ecu's.

I have done the transmission mod but not tested the car yet. The plan today is to check the coolant sensor wires, check for dry joints, do a compression test, replace the spark plugs with NGK BKR6Ek as recommended by the BMW guys, reclean the DK motors as i may not have re-greased them and then do the synchronisation proc.


I'll let you know how it goes.
 
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TriggsyOffline
Post subject:   PostPosted: Oct 04, 2015 - 10:11 PM
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Well over the weekend i have recleaned the DK motors, checked fuel pressure, checked air and coolant sensors, checked ignition coil, replaced a kinked fuel return pipe and replaced spark plugs. A compression test shows 175 across the left bank and 160 to 190 on the right with number 3 particularly oily (but still read 190).

Went out for 2 drives in the warm afternoon and cool evening and still it stalled randomly as i approached junctions.

Only things left are spark plug leads and injectors. I think i'll run it to my local garage and see if they can find any fault codes and check the emissions.

Cheers
Simon
 
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lambo1Offline
Post subject:   PostPosted: Oct 05, 2015 - 12:09 AM
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Hi Simon did you resync the dk's ,its very important, or one bank will be outta sync with the other , also did you find and bad joints in the dme's mine was so bad if I hit them with a screwdriver it would change from 6 to 12 like an on off switch , is it still very rich do you have the voltages mentioned in the bimmer post
and this is some info i found years ago
The way I understand it is, if the DME doesn't receive a signal from the spark detect sensor then it will reduce the injection period on that bank to protect the Cats........so you may feel a clicking at the injectors but that doesn't mean you will be getting the required fuel.
The crank sensor tells the DME the engine is rotating, the DME fires the coil and the distributor makes sure the spark goes to the correct cylinder. The injectors on the other hand need to be fired in time by the DME and the spark detect sensor tells it where the number #1 is.

Sounds like you have a problem with 1 throttle, have you swapped them over. If the EML doesn't get the correct signals back from the potentiometer within the DK throttle housing then it shuts it down. As it seems to start ok but fails after revving I'd be inclined to check it. It would be worth pulling them apart and cleaning all the hardened black grease from around the motor brushes
Took the car to a very releiable 850 specialist. He had the car for a few days and sorted the problem out. The temp sensor on the back of the engine was faulty and would give the computer a very cold reading which in turn would overfuel. Simplest thing!!
 
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TriggsyOffline
Post subject:   PostPosted: Oct 05, 2015 - 08:07 PM
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Hi Graeme,

Thanks for comprehensive reply. I did do the re-synch but i had to drive to a safe area first so not strictly starting from cold if you see what i mean. However, on one of the forums it did say driving for 10 mins or so should re-synch them anyway and that the procedure we follow is for when a garage might fix a customer car and so needs to be re-synched immediately. Don't know how true that is though.

I have hit the DME's but no change, i guess i should really remove them and shake them about a bit to be sure. All my test on the coolant sensors and wiring has been fine, there is 5 volts at the connector so the DME appears to be ok on that front.

I have another theory though. I think the smell is actually burning oil, i have some smoke at idle, not a lot but enough that you can see it. One of the spark plugs was particularly oily, the others vary from light tan colour to black. I only put them in on Saturday so they have got soiled in only a few miles.

I have also noticed a jerkiness on light throttle when coasting which causes driveline shunt. I think i need to test the throttle sensor in case it's giving incorrect readings to the EML.

Other than this stalling problem the cars does pull well but it does feel it lacks a bit of top end performance.

The only other thing to mention is when it stalls i am usually dipping the clutch ready to drop down a gear and you see the rev counter drop quickly. Sometimes it stalls and i have to lift the clutch to bump start it. I know the fuel generally shuts off when you decelerate but my suspicion is when the fuel is told to re-inject the injectors are too inefficient to do it quick enough or supply enough fuel.

Anyway, enough waffling back to do some more googling.

Thanks again
Simon


Last edited by Triggsy on Oct 05, 2015 - 09:39 PM; edited 1 time in total
 
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