Just want to make sure pumps are getting proper voltage
Sent from my SM-G925T using Tapatalk
This could be attributable to a loss of vacuum on one side of the engine (39psi). Try pulling the vacuum line to each FPR and check the pressure again. Also check for fuel in this line (can cause erratic idle) and replace FPR if so.Is a 2 psi difference that much? What would you suggest I do?
You could also check the vacuum in each intake manifold.... should be about -18inHg at idle.
Last edited by BMSman; 08-22-2017 at 01:04 PM.
I've got a theory--
You may have bad Cylinder ID (donut) probes-- (Or they may have been installed on the plug wires in the wrong orientation..)
Since an ignition coil is a big giant flyback transformer, The Spark of the ignition coil generates a ring wave-- With a big peak (several thousand volts), and then some harmonics, including a few cycles of negative voltage. The cylinder ID probes on the other hand, are basically little transformers picking up the energy field coming off the coil wire, and they too will have a similar ring wave but MUCH smaller voltage. This AC voltage gets fed into the DME as a feedback signal, likely down to a TTL 5V level. (You'll also notice in the ETM the resistors BIASing the Cylinder ID probe between 5V and Ground).
The probes (in the ETM) are labeled North/South. If the probes were installed backwards, they may be picking up the bottom half of the ring wave instead of the top half, and the pulse would go the wrong direction.
First off-- I'd measure the voltage of the cylinder ID probe connector to make sure the DME is still putting out that ~5V signal (It'll likely be less than 5V based on the ETM diagram)
Next, If possible, try reversing the cylinder ID probe on the plug wires. If it won't come apart you might be able to do it with a few jumper leads on the X8221 connectors.
Interestingly-- If someone had aftermarket ignition coils, the voltage transferred to the DME might be too high, and could do all sorts of things. But it would or could also mask reversed cylinder ID probes since the ring wave would be higher magnitude in both directions...
Edit: Oh yeah-- And I bough a set of brand new plug wires once upon a time that had bad/reversed cylinder ID donuts.. Car wouldn't start when I put them in, had to put my old ones back in..
Last edited by EEDegreeToDrive; 08-27-2017 at 10:24 AM.
'89 735i, '91 850i, '81 MB 380SLC (For Sale), Tesla Model 3, and VW Passat TDI -- Yes, I still repair General Modules, DM for info!
Sorry guys but I haven't had any time to spend on the car to try anything new. I still have to get my multi metre back from my father to check the fuses. I did swap fuel pumps with my spare and the same issue persists. As for the wires, I've already swapped them twice with 2 works oem sets and nothing. I do drive the car to work every morning. As soon as I start the car and pull out of the garage it runs much better. The trouble all starts when it gets to operating temperature. Then there is a big loss of power. Once it's sits over night again of fine for the first minute. I'll try to get some more work done on it this weekend. Thanks again for all the suggestions
my Twins 850's and its AMG cousin
Reading a little more of your post-- reminds me of a problem my car had..
One of my ignition coils was bad, but it would work for the first ~20 minutes until it got warm (then presumably something expanded and would arc)..
If you can identify which bank is down, try swapping ignition coils and see if your problem moves..
Also, If it's truly temperature dependent, maybe disconnect one or more of the temperature probes and let the car use default values.
'89 735i, '91 850i, '81 MB 380SLC (For Sale), Tesla Model 3, and VW Passat TDI -- Yes, I still repair General Modules, DM for info!
The only thing is I swapped out the coils with new oem, off my other car and the didn't change. This is the nightmare I'm living. It's stumped me and some of the best 8ers. I have 2 8's and usually I can figure things out by swapping from the good car. Plus I have lots of spare parts I've collected over the last 15 years. Its so frustrating.
Last edited by liquidblueloft; 09-01-2017 at 12:55 AM.
my Twins 850's and its AMG cousin
If anything, this post will be a great source of information in case someone else has the same problem
my Twins 850's and its AMG cousin
Did you meanwhile solve the problem? Maybe mixed up the connections of the oxygen sensors? Someone has a picture which plug from sensors in exhaust goes to which plug in the cable loom plugs coming from the e-box on the 850?
I know from the E32 750 that quite often people mix up the connectors when they change the oxygen sensors. So the signal from the o2 sensor goes to the 'wrong' DME
component location view page 7100.0-24
X6220 4-pin connector gray goes to connector from DME # II page 1210.6-15
X6210 4-pin connector gray goes to connector from DME # I
http://shark.armchair.mb.ca/~dave/BMW/e31/e31_91.pdf
Last edited by shogun; 11-17-2017 at 10:42 PM.
Shogun tricks and tips for the E32 series are HERE!
Have you tried changing the spark plugs?
my problems started with a leaking waterpump.
i changed it out.and replaced both coils
then the car refused to start.
i thought that I damaged the brittle wires on the CPS
I changed them out.
still no start.
i changes HT leads
still no start
I checked fuel pumps
1 was seized. Car out of use for a year
i changed both still no start
changed plugs NGK
fires up on 12
only took me 4 years to fix
gone for a repaint now
try changing the fuse on DWA I Think it has a anti tilt divice in the alarm.
i changed my wires to magncore and coils to MSD blaster SS and drove it with no issues for 8 months until i had to fix unrelated problem that took a couple years to sort out.
Since I've had it back on the road, I've been having these issues. i have even swapped it all back to the original oem setup from two working vehicles with no change.
my Twins 850's and its AMG cousin
so here is something new that i just discovered relating to my issues. once the car is warmed up i'm getting a misfire. when i looked under the hood i could actually here the misfire. its actually sounds like its coming from the passenger cap/rotors or wire. It leads me to believe that its its one of those that is causing the issues. This is very frustrating since as you all know i have replaced and tested all of these multiple times with known working parts and getting no change. Now that i can hear an issue i may actually be getting somewhere. I'm going to start with ordering a new set of caps and rotors and begin there. I know the set that's in there has less than 10000kms on the but it is possible one is faulty. I'll need a new set eventually for my other 8 and at least this way i can rule them out. I'll keep ya posted.
my Twins 850's and its AMG cousin
I would visually inspect cap and rotor first, also remove the wire sets and test each wire for ohm resistance while flexing the lead. Should be around 6k ohm.
Coils are cheap enough, I would get those.
Remove the rotor and check the other side of it . If cap and rotor look good no need to get new, that's not your issue.
Sent from my SM-G892U using Tapatalk
Visually i don't see anything wrong with it but like i mentioned, i do hear an intermittent arch sound coming from it. I think that is where i will start since i can get one here locally at a decent price, well decent for Canada
On a side note Dragon850... i just want to say thank you for all your suggestions over the last 2 years. You have been a great source for me with my car. Its because of people like you and the many 850 gurus that make this forum indispensable. I hope to meet you one day and thank you properly.
my Twins 850's and its AMG cousin
i do not believe it... i just bought a new MSD Blaster SS this afternoon (dragon850's suggestion) to replace the one that has barely any kms on it and the car is running 80% better. HUGE improvement. The idle is smooth, i have improved power and the strong fuel smell is gone. It makes sense but no sense at the same time. It should have run better when i put the OEM set back on but didn't. I have no explanation but it worked. i do still have a response issue which leads me to the throttle bodies but MAJOR improvement. When i bury the petal to the floor there is a delay before the power kicks in but at least the first step is completed.
Last edited by liquidblueloft; 04-22-2018 at 06:45 PM.
my Twins 850's and its AMG cousin
I swear, my cars are like a girlfriend.
Sometimes its a rough ride, sometimes its smooth motorin'.
Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
BUT at the end of the day, she loves it when I am inside her.
Time for an update....
Well it's been another year and I'm still dealing with getting this car running. We had a wrenchfest in Calgary last weekend and even had Tom (wuffer) grace us with his guru presence. I trailered my car the 3hr drive to get a fresh perspective. We discovered that after hooking it up to the gt1, that no codes were being stored. As it turns out one and possibly both my DME'S were non functioning. We swapped out a working set and the car runs better but still have the hesitation when accelerating. At least it's finally running on 12. We are realizing that it's more than one problem. We swapped MAF's and throttles again with known working ones. No change. I also replaced the rotors and caps with new ones. Tested all the spark plugs and cables. Also tested the fuel pressure from both line. 3.2bar. also tested the position sensors that I replaced. One was 540ohms and one was 547ohms. Which from what I understand is at the maximum.(550) I also tested a new vemo one out of the package and it was 541ohms. The one thing is the OEM ones on a working car were sitting at 497ohms. Not sure if that is bad but I'm ordering 2 facet ones this week and swapping those. I really don't have much left to try. This is the final stretch. If after I've done the sensor swap and there is no improvement, it will become a parts car. 4 years of this nightmare will have to come to an end. Thank you to everyone that has given me help and suggestions. I'll update in a couple weeks. P.s. any new suggestions are still very much welcome.
May not be a bad idea to make a engine wiring harness your last straw, Tom should have a few and sometimes they crack because of all the heat, Seen it happen a few times but not often, Good luck!
True that, yes I do...
91 850 (Panzer), 2012 Mini Cooper Countryman (WifeMobile) www.wuffer.ca
Bookmarks