E32 750iL "power loss" under heavy acceleration any speed.

[unity]

Starting to really, really hate this car... A couple of weeks ago, or less, I noticed if I punch it hard there is a very noticeable lack of acceleration and it usually cuts out like this while accelerating. That is, I can be at a stop, punch it and maybe even hit a second or third before it suddenly stops accelerating. Makes plenty of noise, but wont go. Sometimes it does not. I would say 50/50. It will do it at highway speed when passing or as I mentioned, lower speeds. It feels like the engine is being retarded. I even tried with ASC off to make sure it was not tripping. Its not limp mode on one side, I know what that is like and this does not feel the same. Once I let off the gas, it returns to normal.

Also if I drop the car into neutral or another gear, the engine seems like its still bogged down.

I did not bring this up when it started to happen since I had a lot of stuff to install this weekend and hoped the issue would get resolved. At this time, the car has:

Bosh (A1 Cardone) rebuild MAFs.
New fuel pressure regulators
New fuel pumps
New fuel filters
New ignition coils

The above was installed before the issue, coils being latest. Tonight I installed:
New Bosch spark plugs
New Bremi dist caps
New Bosch dist rotors
New OEM Beru spark wire set (includes pick up sensors)
New crank position sensors (Facet brand)

I was really thinking the new stuff, specifically crank, would take care of it. I did reset the car by pulling power for a while. It sure starts and idles a lot better. Just still has this weird bog down issue which I noticed during my test drive tonight.

I dont think an O2 sensor could cause this, could it? I am planning to install two Bosch ones tomorrow when I get new O2 bungs installed.

My thought are fuel issue - not getting enough. Replacement pumps are not OEM, but they have the same rated specs. But then I would think it would always be an issue and its not. I still have the old ignition coils, temped to put them in. I replaced them due to age only. Then there is the DMEs, I could have a faulty one or a bad Wokke chip. I may simply have to install the original chips and see what happens.

[shogun]

you bought all good brand parts, except the crank position sensors. There I would go for original. I remember years ago people with M60 engines had trouble with these aftermarket CPS. And it is difficult to test them as a DIYer, 540 +-10% Ohm between pin 1 and 2 is all what we can measure, but to test them over the whole RPM range one would need an osci. Maybe it is time to visit a dealer to get a fault code analysis with a good tester, before you throw more new stuff into the engine bay.
Just to make sure that all the new parts work as they should and maybe you get a fault code with a good diagnosis tool.
I do not think O2 sensors could be the problem.
Any probs with speed sensor ? http://www.bmwe34.net/E34main/Mainte...eed_sensor.htm

Did you check the throttle position poti above the gas pedal? http://www.bimmerboard.com/forums/posts/1081877/
http://www.bimmerboard.com/forums/posts/694988/

[unity]

I could not justify the more expensive crank sensors. And no one seems to say for sure what to avoid, basically all I found was anecdotal stories and no proof (except for one case) of a non-oem crank sensor being bad. Luckily I think we can rule them out anyway since my problem existed before. If need be, I will get better ones even though they are a pain to replace. The OEM ones sure looked better built!

And no worries on throwing parts at this! All of this was planned replacements due to age, nothing else. And the good thing is with pretty much all new stuff its a little easier to shorten the list! I like to keep my cars in "like-new" condition, so I do more preventative maintenance than anything.

I will look at the speed sensor, I have a spare dif from another E32. So I might even had a spare, not sure. But I dont recall my speedo every acting up, or wipers, etc. I will take a closer look when it happens again for sure.

The throttle sensor sounds like a better bet, great links! But I do have an M70, so or me it would be the pedal potentiometer, correct? I should have added that in the past couple weeks my fuel economy is crap! I get about 11 at best now. Before I could hit 18 no problem, even 20 is I was really careful. But worst case was no less than 15mpg (mixed aggressive and normal driving during a work week). And I have dropped into a full limp probably 4 times over the same period. Oh! And the car does sometimes not go into overdrive for a long time. Hmmm....

- - - Updated - - -

Is this the right part number?

12721747630 "Accelerator pedal sensor" "Accelerator pedal potentiometer"

What its made of, sold gold?

- - - Updated - - -

Any known compatibility of the potentiometer? That is, is it specific to engine model (M70) or series (E32)? Just so I can broaden my search.

[shogun]

12721747630 Accelerator Pedal sensor From:11/01/1991
Part 12721747630 was found on the following vehicles WITH EML:
•7' E32   (11/1986 — 03/1994)
•8' E31   (07/1989 — 10/1996)
I have to mention, that is a shot in the dark, usually these sensors do not break or only in rare cases. Just measure it.
Fuel econonmy bad: did you disconnect one the O2 sensors? Just asking, in case you connected them wrong, left to right and right to left? Just checking. I made that mistake once and that caused some trouble, because the sensors reported to the wrong Motronic. Maybe you just switch the connectors for a test.
Because I am wondering about the fuel consumption. But.... I am just searching and thinking about possible causes, we should not take everything for granted.

[unity]

On mine, there really is no way to mess up the O2 sensor connections unless they come with really long cables. They are laid out just like the crank sensors, that is the cables are only so long and they only reach so far. BMW was smart to position the O2 hookups in a way that one is further from the other, they are staggered. Even still, I did one at a time. And I have not touched them since install many months ago. I am replacing them, again, because removal was horrific and upon install one got cross-threaded. The original bungs got beat up bad. I also suspect one got damaged (cracked ceramic). Because after install, I almost immediately got an O2 code. So I decided to just get new bungs installed with two new Bosch sensors. The ones I have now are Denso. Even with the O2 code, I was getting the milage I mentioned above - until this last two weeks or so when the car completely changed its demeanor. Even now though, if it does not bog down its pretty damn quick and seems to run fine. Also, when I pulled plugs one side was perfectly fine but the other side (passenger bank, which also has O2 code) were black and carbonized. I wanted to do the O2 sensors when I did new plugs/wires/etc to ensure the new plugs would not get ruined.

Note: I will add that my idle hunts a lot to the point of wanting to stall. New MAFs helped in this area originally but never cleared it up 100% and now things are back to nearly stalling. But if I tap the accelerator just enough to bump RPM, its fine. Its just idle that is bad. And like the bog down, this is not 100% of the time.

IMG_1693.jpg


As for the potentiometer, I will certainly test mine out first and see what I get for readings. I just want to be on the hunt for a replacement just in case. If I could have found a used one tonight for under $100, for example, I would have picked it up but still tested the one I have now. Looks like I can test it from a port above in the engine bay which will make it pretty easy to do.

[tsmcg161]

An easy way to check if your cats are clogged is to remove the o2 sensors and drive it. It will be noisy but thats one you can cross off your list.

[unity]

Well today the new O2 sensors went in. In a new location, so the old Denso units are still in place for now (I have plugs to install). Love the new location, not that I will ever replace these. Anyway, another reset later and the car is working pretty well. I can not get it to bog down, yet. But I still suspect there is some issue. I had a REALLY hard time doing stomp codes, even my friend was surprised how hard it was compared to the past. I did not have time to pull the potentiometer or test it, did a power steering pump rebuild instead. I hope to have time this week or next weekend to dive into the pedal potentiometer.

[unity]

Just reporting that today I still had the issue. While I have spares, I ordered two new temp sensors (not the third for cluster temperature). Just something to help rule things out and good preventative maintenance. I will add that from work to home I did 17.8mpg.

[85k100rt]

Just a thought. On my 1990 750il, BMW decided to restrict full throttle until the vehicle reaches a predetermined speed (40 mph if I remember correctly). My Wokke chipped electronics eliminate the issue, allowing for full throttle response without regard to vehicle speed. I don't know exactly how this works, but with my chips, if the speed signal doesn't get to the electronics (EML thinks speed is zero), then the throttle restriction is still applied. I had an intermittently defective speed sensor on the differential which resulted in the same symptoms you are having except that my speedometer did not function during the failure (read 0 MPH). I replaced the sensor and cured the issue. Your issue may be similar in nature. I 'd suggest you investigate the possibility that the speed signal is being interrupted somewhere. I'd start by trying to duplicate the failure intentionally. I'd interrupt the speed signal going to the engine electronics and compare the resulting performance to your failure. If the forced results are similar, you'll at least have an area to investigate.

[unity]

Hmmm.... I will look into that. My speed reads fine during the issue, but maybe I should pull it up on the OBC also. Also I do need to look closer as to when it happens temperature wise. I certainly can say it happens after cold starts, not sure about it after being heated up. I dont recall.

[85k100rt]

OK, strange you mentioned cold starts, my failure was only when temps dropped below the 40-50 degree range and only lasted a few blocks of driving. When the speedometer started working, I had full power back. If you have a Bentley manual, the wiring for this on your car can be found on ELE-92 and ELE-93.

[unity]

Update. Does not seem to be cold start related. I will add that since adding the O2 sensors, the car is still top notch on fuel economy. Did a trip around the state today and average over 18. At one point I reset milage and did 19mpg for a long stretch, not all highway. So that is good. But one very odd, very new thing happened today. It bogged down non-stop and went from "something feels a little off" to "yeah, there is no power" over about 2 hours of driving. That is unlike before where the effect may kick-in and out, it was stuck. And it started out no so bad and got progressively worse. Very hard to get going on highway on-ramps, etc. Speedo and all gauges read fine. It was just stuck in this bogged down state. A restart of the car did not fix it. However, I wanted to give it a longer shutdown time and did so during a fuel up. After that, it was fine for the entire remainder of the trip. Not sure what it could mean. New temperatures sensors will be here this week. After that, I will take a closer look at speedo sensor and gas pedal pot.

[unity]

Still great economy and power. But the car dropped a bank today. Replaced temperature sensors last night for EML, DMEs. I have not driven long enough to notice if there is a bog down issue still since new sensors went it.

[unity]

Bogged down twice today. Once for quite a while unless throttle was backed off. But since I was entering a highway, it was not ideal to do so. Then for a short bit on another drive. Also dropped into limp mode twice today. I think I will order that cable soon and get a laptop looked up to see what the EML says before I go further. But in the mean time, I may try to clean acceleration pedal potentiometer and run tests on it.

[w12a3d]

My friend was had a similar problem on his 850i, he tried everything, including MAFs, fuel pumps etc.. Guess what! Voltage regulator, but doesn't mean that is your problem, just check that.

[unity]

Im willing to look at anything. The alt is a new rebuild, but I will drive with voltage up on the OBC. I will say that there is no change in lights when I have the issue though. I would think the regulator would result in voltage issues across the board. I did order the laptop cable to check EML codes. So that may help too.

[shogun]

Somewhere I assume there is a electric problem like a wire broken which sometimes has no contact, for example when engine is moving clockwise or anti-clockwide.
Best is when you can check it with the laptop for stored faults.
Some things from memory
http://www.bimmerboard.com/forums/posts/644209/
on one of the B12 of my wrenching buddies the metal bracket got lose where the round ports are for the diagnosis port, X20 and X21. This bracket is just held by plastic nuts. When they got lose the bracket was vibrating and the wire loom of these 3 connectors got damaged.
Here you can see that the main wire loom for the engine is directly below these 3 ports http://s71.photobucket.com/user/shog...l?sort=4&o=204
Also check this battery cable is firmly bolted on http://s71.photobucket.com/user/shog...l?sort=4&o=205

[unity]

I could be as simple as a wire. It runs so well when it does run right. I will dig around the harness and see if I can make it stumble and fail. I have found broken wires in the past, such as one to the passenger bank air temp sensor at the back of the intake. It generated a code though, so it was not too hard to know there was an issue there. The only fault code I have is 2222 (I did stomp until end of code check flash), the other bank was all clear (1444).

I would really love to create a who new engine harness from scratch, but I dont have the time. And I have made engine harnesses before.

[shogun]

accel pedal position sensor testing

E32 Bentley Repair Manual shows the data for testing on page 130-45.

EML Pedal Position Sensor Test
pedal at idle position
manual transmission 0.34-0.43 VDC
automatic transmission 0.35-0.45 VDC

pedal at full throttle
manual transmission 3.1-3.3 VDC
automatic transmission 3.7-3.8 VDC

EML connector pedal position test pin
M70 DME 1.2 brown/violet pin 1
M70 DME 1.7 blue/brown pin 20
M30 DME 1.3 blue/brown pin 20

terminal numbers are molded in the EML connector face. These numbers are very small and may be difficult to read.

set a gap of 3mm / 0.118 in. between accelerator pedal bracket and the idle stop.
To check adjustment, peel back rubber boot from EML harness connector (round big plug left side engine bay close to the diagnosis port) and connect digital voltmeter between specified pin in connector and ground.

[unity]

Sweet! I will have to test it. But for whatever reason, the issue has not come up at all a short while after posting this. Car drives me NUTS sometimes!

[SergeBMW]

Just my 2 cents but maybe you have an issue with one or both of your throttle bodies? The DKs. Maybe they are dirty inside or one of the brushes isnt making good contact causing intermittent issues and the dropping of a bank occasionally but not so severe as to maintain it in limp mode.

This is how I realized one of my DKs was in bad shape before my cleaning. Check these measurements (resistance). I would also just go ahead and clean them while you are at it.
http://twrite.org/shogunnew/files/boschthrottlebody.pdf

How to clean/refurbish
http://twrite.org/shogunnew/files/fo..._Refurbish.pdf

[unity]

I already re-built mine, twice, and measured them too. They read great and Shogun said the wiper areas looked almost new (really good condition).

Really besides a big LAD leak and loud lifter, the car is running well. 17mpg, lots of power. And my new lifters came today!