325 dies under way,..

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Hello, I thought I had this sorted but these same symptoms have cropped up again: I'm cruising along with my sunglasses on and my toe tapping and then the engine stops running. I coast to the side of the
road while people jeer and laugh and crank the starter. It spins but doesn't fire. I crank for 10 secs and wait 60 secs and try again. After about 4 minutes of this it starts and runs fine, sometimes for weeks, sometimes for minutes. It died 5 times yesterday after running fine for a month. I checked the main relay connections and they're still shiny from my last clean up. The car was brought to an expensive shop with this problem last summer and it tested no error codes but did a similar thing for the mechanic- it would drive fine but stall at stop signs- start hard and then drive again. He jiggled the wires- which is my specialty, and the car ran fine again. He noted, "tach signal probably getting lost,.". Any idea where the sensor for this? From the Bentley manual I've tested the cold start sensor and the sensor that's on the front of the cam for resistance and they are within range at the specified temp. There's another sensor- maybe crank position- down near the crank pulley, that's not even supposed to be on my model. I'm open to suggestion. Thanks for your time and happy motoring to those of you in a position to do so.
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Hello, I thought I had this sorted but these same symptoms have cropped up again: I'm cruising along with my sunglasses on and my toe tapping and then the engine stops running. I coast to the side of the road while people jeer and laugh and crank the starter. It spins but doesn't fire. I crank for 10 secs and wait 60 secs and try again. After about 4 minutes of this it starts and runs fine, sometimes for weeks, sometimes for minutes. It died 5 times yesterday after running fine for a month. I checked the main relay connections and they're still shiny from my last clean up. The car was brought to an expensive shop with this problem last summer and it tested no error codes but did a similar thing for the mechanic- it would drive fine but stall at stop signs- start hard and then drive again. He jiggled the wires- which is my specialty, and the car ran fine again. He noted, "tach signal probably getting lost,.". Any idea where the sensor for this? From the Bentley manual I've tested the cold start sensor and the sensor that's on the front of the cam for resistance and they are within range at the specified temp. There's another sensor- maybe crank position- down near the crank pulley, that's not even supposed to be on my model. I'm open to suggestion. Thanks for your time and happy motoring to those of you in a position to do so. -----
Year, model, engine, transmission?
Bill in Omaha '86 535i
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shifter, 6 cylinder 2.7L. I think it's motronic but it won't give you error codes by steping on the gas pedal. 145k miles. It says 325e on the door sticker but 325 on the rear of the car. The sensors seem to be present in a mix of '87 an '88. I think this may have been a change-over year. Thank you.
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shifter, 6 cylinder 2.7L. I think it's motronic but it won't give you error codes by steping on the gas pedal. 145k miles. It says 325e on the door sticker but 325 on the rear of the car. The sensors seem to be present in a mix of '87 an '88. I think this may have been a change-over year. Thank you. -----
If you might need a new ECU, let me know the ECU number. I have a couple and at least 1 is for your car, I believe. I also have a set of wires and maybe a cap and rotor, plus a few relays. It's all cheap as I no longer have that car (or can use them on the 535i). Sounds like a relay or sensor. Cross-over years are a PITA to troubleshoot, too, even with a Bentley. I'd make a list of what was done before you bought the car and start from there. Replacement parts from that point are a very short list. Oxygen sensor would top the list (exhaust smell), clean the Air Flow Meter with carb cleaner/WD-40, replace fuel pump relay (which also matches a few other relays in there, so you can switch test with those), fuel filter. I find my plastic connectors are starting to crumble that go to the crank position sensor and the other one (RPM, I think). They look like the same ones as fuel injector connectors. They could be internally corroded or breaking apart. A sticky AFM internal flap door may be binding, too. You'll find out when you clean it.
Bill in Omaha '86 535i
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cosmo <beyond the pale> wrote:

What does the tailpipe smell like when this happens?
If you swap the fuel relay and some other relay, does the car start up?
If you pull a spark plug out, is there a spark when this happens?

That's a reasonable guess. What year car is this? The older ones have a tach sensor and a crankshaft position sensor both, and either one can cause issues.
If these sensors are not providing signal, there will be no spark when you pull a plug.
So, what did the mechanic from the expensive shop do? He said it was probably a sensor, then washed his hands and went home?

You have to do the testing when the problem actually occurs, and that means carrying stuff with you so that you can do the testing by the side of the road. All kinds of things can cause these problems. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 21 Dec 2007 21:11:32 -0500, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

tapping and then the engine stops running. I coast to the side of >>the road while people jeer and laugh and crank the starter. It spins but

It smells sickening. Kind of sulphuric, I guess. I did notice a different smell while cranking. It's about 35 degrees here.

and you're trying to catch a ferry. From receipts, this car had a new fuel pump, tank clean, new sock. Don't see anything about a filter.

I'll check next time.

tested no error codes but did a similar thing for the >>mechanic- it would drive fine but stall at stop signs- start hard and then >>drive again. He jiggled the wires- which is my specialty, and the car >>ran fine again. He noted, "tach signal probably getting lost,.". Any idea

I'm working from the Bentley book. My car is an '88, 2.7L, auto. It says 325e on the door sticker but 325 on the boot. The sensors are a mix of '87/'88. The bottom sensor for the crank is missing; the side sensor for the crank is there. The '88 cam sensor is there but it uses an extra sensor for the cold start like an '87.

No, he told them to sell the car as it would cost them too much at $85 per hour to find a problem that didn't produce an error code. They had already spent $900. He charged them $300 something for the pump.

Always the voice of reason. Thanks again, Scott, I'll pack my kit.
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cosmo <beyond the pale> wrote:

tapping and then the engine stops running. I coast to the side of >>the road while people jeer and laugh and crank the starter. It spins but

Okay, so it's getting fuel, and it's misfiring. I agree this sounds like an ECM or sensor issue.
Next time it happens, open up the glove compartment, and bang on the ECM with a wrench a few times. They are subject to cold solder joints.

Umm... wait a minute, you just got this car?
I am thinking it's probably not a fuel pump or fuel pump relay issue. If they changed the pump, I am surprised they didn't change the relay as well, too. I'd still swap relays when it happens, though.

Okay, if this is what I think it is, the ECM is just a little Intel 8051 with 4K of memory running in a little loop that doesn't do a whole lot and has no facility for producing error messages. So you can't look at the sensors with an analyzer, you can't pull codes off the ECM, because the hardware just isn't in the ECM for that.
This means your job now becomes a process of either swapping sensors out (and maybe the ECM module... did the original mechanic do that?) and seeing if the problem occurs, OR trying to catch the problem while it is happening and looking at all the signal lines.

So you bought the car and now YOU can spend the money?

Oh, also... don't forget the oxygen sensor! It can cause this sort of problem, believe it or not. I'm not really sure why. Also, clean all of the connectors that even LOOK like they might carry sensor signals. Corrosion on connectors is a big deal. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 22 Dec 2007 10:53:59 -0500, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

This is most definitely a Motronic unit. Don't know where you got the above description but in the grand scheme of things it's partially correct. Any ECU that's running a fuel injected engine operates in a fairly simple fuel mapped mode that uses the oxygen sensor to slightly modify the fuel injector timing to keep the proper mixture. They use an array of sensors to determine engine temperature as well as the position of the crank or cam as a timing reference and to measure the amount of air the motor is pulling in. If everything is working properly, the injectors spray the correct amount of fuel at the proper time and the coil fires the spark plug at the right moment and the motor runs. Different versions of Motronic have different capabilities for self diagnostics and use different sensors but they all function basically the same.
In this case, the motor appears to run well until this occurs. The original poster has said nothing or the motor searching for idle so I believe we can remove the suspect of vacuum leaks. Either the Motronic relay or the fuel pump relay would instantly cause the car to shut down and not restart. If there is spark, the Motronic relay is not at fault. The actual ECU would not be at the top of my list. There is a connector underneath the intake manifold that has a history of collecting moisture and corroding, check the pins in there to make sure it's clean. Not sure what signals go through there on your model. Crank reference sensor on my 89 had a broken wire right at the sensor itself and until I replaced it and bent the wire back I never knew it. This caused the car to run fine for a while and then do exactly what yours is doing. Biggest pain in the ass I ever tried to find. Got one from a junkyard and changed it (figured at $100 for a new one, what the hell) and the problem went away. The compound where the wires go into the back of the sensor was all missing on my original sensor.
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I got it from taking a bunch of ECUs apart.

Yup.

What self-diagnostics are in there? According to my dealer mechanic and one local independant mechanic, there is no error reporting at all from the earlier Motronic boxes. The later ones have a 3.5mm connector on the back of the ECU connected to the UART on the 8051, but nobody seems to have anything that can be plugged into it.
Also there is the "diagnostic connector" under the hood, which appears only to be useful to provide a spark sensor, TDC sensor, and to reset the oil change and inspection lights. I don't see any other signals besides those, at least on my E28. The dealer tech said that there was an analogue diagnostic machine that plugged into it at one time but that "nobody has any of those any more."

I agree that the ECU is not high on the list, but the majority of ECU failures seem to be due to cold solder joints and are easy to diagnose with a sharp rap.
The multipin connector under the intake is a really good call, I like that one.

Makes perfect sense. Can you explain why a bad oxygen sensor can cause the same problem? I have seen a 328 where the sensor wiring was damaged in such a way that the vehicle would run fine with the sensor removed (and the ECU presumably ignoring it), but would die intermittently with misfires with the sensor in place. That one still makes me scratch my head. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 23 Dec 2007 10:13:32 -0500, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

Your mechanic may be correct on the early boxes. However, they test the sensors and light the check engine light but you can't get the code for what sensor is reading bad without a code reader. I have seen these on EBay as well as a few other sites but don't know what their capable of. Later versions allow you to read the code on the check engine light by pressing the accellerator pedal all the way to the floor five times an a certain amount of time. The ECU then flashes the check engine light in pulses that can be counted and the code looked up from there. I see from a later paragraph that you have an E28, these definitley had an early motronic version. At least it isn't J-Tronic (what a difference!!!).

I've wondered what information could be gathered from there but since I haven't seen much talk about it from the tech community, I didn't figure it was all that important.

True, worth checking for sure. If it has cold joints, anyone comfortable with a soldering iron (the proper one for the job) can reflow the joints and be off and running.

I've never had a problem with it but I did clean a lot of gunk out of mine when I had the intake off...

Only thing I can think is that the sensor shorted to ground or became open (whichever causes the ECU to richen the mixture) and the mixture becomes so rich it won't fire. That's the ONLY thing I can think of for that. I did see an oxygen sensor so screwed up that as soon as it got up to operating temp and the ECU tried to go closed loop and run off the oxygen sensor input the car would flood out and die. Unplugged it and the check engine light came on but the car ran. A new sensor (for a 1990 5.0 mustang) solved the problem. $35 for the sensor and five minutes rewiring the plug beats $90 for the same sensor with the BMW plug...
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Yes, the E28 has no check engine light. Mine _does_, however, have the useless 3.5mm jack on the back of the ECU but apparently not all do.
The later units that allow use of a code reader.... where does the code reader plug in?

I don't think anything much useful can be, other than TDC. Which admittedly can be a very useful thing to know in conjunction with looking at other signals.

I can see that. That is _very_ rich.... --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Scott Dorsey wrote:

Was there ever designed an engine-management system that would drop dead if a single sensor went bad? I thought they all have "limp home" modes, should that happen.
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dizzy wrote:

The engine-management system on my Audi 100 2.3E did not. The hall sensor died and it was impossible to make it start. Before that I had had some intermittent problems, but I was never able to find out what it was before the engine died and I was stuck on the middle of a bridge during rush hour...
--
BBO, DoD#2101



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There are always going to be certain things that will kill it dead. Only way around that would be completely redundant systems. The "hall-effect" sensor (known comonly as a reference sensor) will kill the car dead as the computer has no idea if the motor is turning over or not. Also, even if it tried to assume that the motor was running, it would have no timing signal to base anything on. Some sensors will make the car run rough or sluggish, others kill it dead...

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With the old Motronic system, though, a lot of things will kill the engine dead that on more modern and robust engine controllers will enable a limp-home mode. For example, the oxygen sensor failures or the failure of the air mass sensor.
What do you want from 4k of code? It's not a Cray in that box. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Oh, yeah, stalls at stops. I bet it idles a little high when started cold and the RPMs hunt. The Idle Control Valve may need a cleaning. On top next to intake manifold, it's a silver cylinder about 5 inches long with a big hose in and out, maybe like a "T" shape with a 3-pin connector on the other end.. If it sticks, clean before replacing, it is very expensive.
Bill in Omaha '86 535i
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a high miles engine. When it dies, there's no sputtering or trying to stay alive. It all just stops in mid stroke and you coast along in silence.
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It does sound like an intermittent connection. I would suggest that you may find it by trying to induce the failure while it's running normally. With the engine idling nomally, just start wiggling any and all electrical connections and wiring runs. Don't forget under the dash and around the ignition switch. I wouldn't suggest beating on the computer but you could flex it a little and flex the harness going through the firewall. Crank and cam postion sensors should be rapped with the back end of a screwdriver.
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Jack wrote:

my 88 325is did that for about 2 weeks before/as the fuel pump died
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cosmo wrote:

Although I do not know if there is an hall sensor in the '88 325 it sounds exactly like it. I had the same problem on my '93 Audi 2.3E. I was so lucky that it started afterwards, but when it finally bought it, it did so on the middle of a 2 lane bridge at rush hour. Do you think I was the most popular guy around at that time? :-D
--
BBO, DoD#2101 1990 BMW 318i 1987 BMW 325i Convertible

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