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7 Series - E38 (1995 - 2001)

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  #1  
Old 08-31-2013, 04:27 PM
CitizenOfDreams CitizenOfDreams is offline
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1998 740i misfires

I just bought my first BMW - a 1998 740i. The car looks OK on the outside, but has 200K miles and all kinds of problems. So I may have bitten more than I could chew...

The main problem I'm having is the engine. The car runs rough under load and idles rough. INPA shows misfires on cylinders 1 and 6; the "smoothness" meter on those cylinders is very high and often goes off the scale.

Now the interesting thing: if I shut off the engine and restart it immediately, it starts idling much better (although the "smoothness" numbers are still high on cyl 1 and 6). As soon as the car is put under load, rough idling returns.
Update: from what I've read here on the forum, it's the DME that turns off the cylinder when it detects too many misfires.

Here is what I found out:

- The car has a badly leaking water pump (I got one ordered, waiting for delivery). The coolant has been splashing under the hood and may have damaged some electrical components.

- The engine may have been overheated in the past. There is a melted spot on the back of the intake manifold, near cylinders 4/8.

- The engine does not smoke.

Here is what I did so far:

- Changed the fuel filter.

- Measured the fuel pressure: normal (50psi with vacuum, 60psi without vacuum).

- Changed the fuel injectors (a rebuilt set).

- Swapped the spark plugs and the coils between cylinder 1 and a good working cylinder. The problem stayed with cylinder 1. The spark plugs look healthy.

- Looked for a vacuum leak, haven't found one.

- Tried disconnecting the MAF sensor, still rough idle and misfires on 1 and 6.

Any advice from the experts? What should I do next, what do I need to look for?

Last edited by CitizenOfDreams; 09-01-2013 at 01:11 AM.
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  #2  
Old 09-01-2013, 10:34 PM
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supertech777 supertech777 is offline
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Re: 1998 740i misfires

How about the camshaft position sensor , what are the codes ? Have you pulled any codes ?

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  #3  
Old 09-01-2013, 11:28 PM
CitizenOfDreams CitizenOfDreams is offline
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INPA codes are:

36, 38 - "Katschaedigende Aussetzer" in cylinders 1 and 6
75 - Summary "Katschaedigende Aussetzer" error
50, 55 - "Aussetzererkennung" in cylinders 1 and 6
62 - Summary "Aussetzererkennung" error

The codes do not come back when the car is idling. It's idling a bit imperfect, but no misfires are detected.

As soon as I start driving, cylinders 1 and 6 misfire and the same codes come back.

I do not get any crankshaft or camshaft error codes.

I looked at the camshaft sensor with an oscilloscope, it seems to put out a proper square pulse.

I have not looked at the crankshaft sensor yet, that would be my next step. Would a bad crankshaft sensor cause misfire in two specific cylinders?

Last edited by CitizenOfDreams; 09-01-2013 at 11:33 PM.
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  #4  
Old 09-01-2013, 11:54 PM
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supertech777 supertech777 is offline
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Re: 1998 740i misfires

What I know about crank sensors are they either work or they don't , have you tried ohming both sensors ? I know you scoped the cam sensors . I maybe shooting in the dark here

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  #5  
Old 09-02-2013, 12:39 AM
CitizenOfDreams CitizenOfDreams is offline
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Haven't "ohmed" the camshaft sensor yet, and haven't played with the crankshaft sensor at all. Is there an accessible point under the hood where I can see the crankshaft sensor signal? I hate crawling under the car if I can avoid it.

Update: both the camshaft and the crankshaft sensors seem to be active devices: +12V and GND come in, logic signal comes out. Those sensors are not just simple pickup coils like they used to be in the past, so I don't think resistance measurement would give me too much meaningful information.

Last edited by CitizenOfDreams; 09-02-2013 at 02:03 AM.
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  #6  
Old 09-02-2013, 07:09 AM
CitizenOfDreams CitizenOfDreams is offline
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I've found numerous threads in the Internet about misfiring BMWs, and they all go more or less like this...

- My bimmer is misfiring. Help!
- Try checking this, this, this, this and this (a 5-page list).
- I checked all that, haven't found anything bad.
- Try replacing this, this, this and this (a 5-page list).
- I replaced all that, nothing changed.
- (crickets)
- I went to the mechanic, he swapped the engine, the transmission, the exhaust, the wheels, the seats, the windows and the radio. Charged me $40,000. The car still misfires.
- (crickets)
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  #7  
Old 09-02-2013, 12:57 PM
CitizenOfDreams CitizenOfDreams is offline
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Labor Day update (happy holiday to all North Americans here).

I just measured the engine compression. 7 cylinders out of 8 showed 210..220psi. Cylinder #2 (which has not been misfiring) showed 180..185psi and improved when I splashed some oil in it. Worn rings?

So, I'm back to chasing my tail...
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  #8  
Old 09-03-2013, 03:30 PM
CitizenOfDreams CitizenOfDreams is offline
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Status update.

I may (or may not) have found the problem (or at least a problem). But first, a little rant.

Redneck mechanics should stick to fixing redneck cars. You know, points, carburetors, big blocks, three-on-the-tree, pedal-to-the-metal and chevy-to-the-levee stuff. A modern car, let alone a metric modern car, is way beyond their comprehension. Allow me to demonstrate.

This is how the German engineers expect you to change the crankshaft position sensor:



And this is how a redneck mechanic does it:

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  #9  
Old 09-04-2013, 06:43 PM
CitizenOfDreams CitizenOfDreams is offline
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Another fine example of workmanship:



You are a redneck mechanic. You have a broken car you are trying to fix. You don't know what's wrong with it. Worse than that, you don't know how to find out what's wrong with it. So you go to the nearest junk yard and start swapping parts.

You pull out your old cam position sensor, leaving the O-ring in place. (The sensor is probably just fine, and your problem is totally unrelated to it. But what do you know?)

You pull the sensor from a donor, this time with the O-ring. You stick it into your engine, on top of your original O-ring. The sensor does not fit. You press harder. It still does not fit. You torque the bolt till the sensor cracks, call it good and open a can of Icehouse.
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  #10  
Old 09-04-2013, 09:15 PM
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supertech777 supertech777 is offline
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Don't worry its all about the learning curb , next time u know . It's all good !
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  #11  
Old 09-04-2013, 09:27 PM
Mayorchuck Mayorchuck is offline
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Crank sensors should read around 5-600 ohm. It will be way our of range if it's bad.
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  #12  
Old 09-05-2013, 05:00 AM
CitizenOfDreams CitizenOfDreams is offline
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Quote:
Originally Posted by Mayorchuck View Post
Crank sensors should read around 5-600 ohm. It will be way our of range if it's bad.
Mine measures 660 ohms and generates a strong signal. Problem is, I don't have a modern scope to see the exact timing of the pulses.

Problem is, the sensor is physically damaged from contacting the flywheel. And what's worse, I don't know how badly was the flywheel itself damaged. It may even have a broken tooth, which would explain the misfire detection problem. I will need to inspect it thoroughly. Meanwhile I have a used crankshaft sensor coming from eBay.

Right now I am working on changing the water pump. Pulled the old one out last night, the bearing was completely shot.
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  #13  
Old 09-05-2013, 08:37 AM
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FABOCH FABOCH is offline
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Flywheel tooth missing wouldnt cause a misfire
Transmission issues , yes IMHO the flywheel is between the back of engine and transmission
Since when did the Cps sensor move location ? On my M62tu engine , both(2) Cps sensors are installed on bank 1 and bank 2 upper timing covers. They sense the Cam wheel and cams location . In my engine for example , the m62tu Vanos, if the Cps wheel discs are BeNt (lopsided)it will throw a code
It's the end of your sensor chipped?
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Last edited by FABOCH; 09-05-2013 at 08:45 AM.
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  #14  
Old 09-05-2013, 09:01 AM
CitizenOfDreams CitizenOfDreams is offline
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Quote:
Originally Posted by FABOCH View Post
Flywheel tooth missing wouldnt cause a misfire
How about (false) misfire detection?
Quote:
Since when did the Cps sensor move location ? On my M62tu engine , both(2) Cps sensors are installed on bank 1 and bank 2 upper timing covers. They sense the Cam wheel and cams location.
There are camshaft sensors and crankshaft sensors, both confusingly abbreviate to "CPS".

The crankshaft sensor, among other things, detects misfirings by measuring precise time intervals between the pulses. If one of the teeth is missing, I would imagine it would seriously disturb the misfire detection routine.

In my photos above:
- The one with the chipped tip is the crankshaft sensor.
- The one with extra O-ring is the camshaft sensor (my pre-VANOS engine only has 1, not 2)

Last edited by CitizenOfDreams; 09-05-2013 at 04:20 PM. Reason: edited for clarity
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  #15  
Old 09-06-2013, 03:00 PM
CitizenOfDreams CitizenOfDreams is offline
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Well... That escalated quickly.

I installed the new water pump, filled the system with coolant and got a nasty surprise. The radiator (Behr, made in 2008) has corroded through. Got one ordered (a $70 aftermaket replacement, not the OEM Behr).

As I said, I may have bitten more than I could chew with this car. I expected a daily driver that I could fix at my own pace. Instead, I have to spend hundreds of dollars and hours of work just to get it on the road.
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  #16  
Old 09-06-2013, 03:54 PM
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FABOCH FABOCH is offline
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My Behr Radiator(So Cal 7) is still on my car believe it or not...11/13/2003 build date..I have 177k miles...
You can solve "the missing tooth" hunch very easily....Grab a 27mm socket , remove spark plugs- so u dont get any combustion issues, roate the crank while having someone under neath with a flashlight and see if theres ANY missing teeth
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  #17  
Old 09-07-2013, 11:58 AM
CitizenOfDreams CitizenOfDreams is offline
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Quote:
Originally Posted by FABOCH View Post
My Behr Radiator(So Cal 7) is still on my car believe it or not...11/13/2003 build date..I have 177k miles...
I think the reason mine died is that it was run on diluted coolant and/or plain water for a while due to leaking water pump.

Quote:
You can solve "the missing tooth" hunch very easily....Grab a 27mm socket , remove spark plugs- so u dont get any combustion issues, roate the crank while having someone under neath with a flashlight and see if theres ANY missing teeth
Yep, I will certainly do that. Check if any teeth are missing (besides the 2 that are absent by design), and how badly are they damaged.
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  #18  
Old 09-07-2013, 12:12 PM
CitizenOfDreams CitizenOfDreams is offline
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Now it's time for another rant.

Here is a typical BMW connector:



Very simple yet ingenious design. You push the metal spring with your finger, and the connector slips right out. So easy a caveman can do it. Heck, it's so easy a caveman's grandmother can do it. But our redneck mechanic has his own way. He gets his trusty Craftsman screwdriver, pops the spring off and discards it. When (or if) he plugs the connector back, he just shoves it in, counting on friction and dirt to keep it together.
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  #19  
Old 09-08-2013, 07:29 AM
US&Germany US&Germany is offline
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This is an incredible thread. CitizenofDreams, you have a few "metric tons" of courage. My compliments to you.
This commenter bought a 1998 740il (US) a little over a year ago.
From a lady M.D. and her brother. 50,000 original miles. BEAUTIFUL car. "Killer."
Bought a code reader, "our" third BMW this is, but the first that I've done any "real work" on personally.
The 740il ran great, until driven, er uh, "with some spirit."
Then finally comes the misfiring, and check engine light. Misfiring continues until the car is stopped and restarted. (Perhaps the OSV/CCCV/Oil Separator/PCV)(??)
Then one night out with family, we had to have it towed home as it wouldn't start. A slew of codes. So, replaced the camshaft positioning sensor.
Replacement of the Camshaft Positioning Sensor with a new OEM Camshaft Positioning Sensor, that fixed the ""doesn't start" problem.
Still idles a bit rough at times, the engine light remains lit, and if hard acceleration is done, the check engine light "flashes."
Car will shudder and lose power on the highway, sort of dangerous, until the engine is stopped and restarted.
Figure from what I've read is there's a clog in the tubing around the OSV, and/or the OSV is shot, maybe, right?
Have a new Hamman OSV from Amazon of all places, NICE price too.
But, one thing before I replace the OSV...
I saw a video that depicts and states that a bad OSV will make the dipstick tube (with dipstick removed) "suck the tip of your finger real hard." (I'm trying to be "decent" here.)
So, since my dipstick tube isn't really sucking much, and much reading of others similar plights with the E38, I'm wondering if the catalytic converters or the O2 sensors are somehow mixed up in this.
But the way my car runs almost "normal" after restarting, I've read that in itself is indicative of a bad OSV after all.
I guess right now I'll just replace the OSV and see what's up from there?
Pretty sure there's a hissing sound now from the back of the block by the OSV/PCV too.
Thought it may be the climate control, but pretty sure there's a vacuum leak now.
Going to look at it this morning before the thermometer reached 98 degrees or more.
Chime in anytime, anyone. Thank you.
By the way, (with more spirited driving)this car had the upper radiator hose blow off the radiator with the plastic threads still in the upper hose, so it does have a new Nissens radiator and associated parts.
And through my own impatience and ineptness, I managed to break, (and replaced) the glovebox latch by, apparently, inadvertently trying to get it to shut with the metal owners manual mini-briefcase zipper "pull handle" up in it.
Other than that, what's not to love?
Age, not mileage, like "dear ol Dad" once said.

Last edited by US&Germany; 09-08-2013 at 07:42 AM. Reason: left out something
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  #20  
Old 09-08-2013, 08:01 AM
CitizenOfDreams CitizenOfDreams is offline
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Quote:
Originally Posted by US&Germany View Post
This is an incredible thread. CitizenofDreams, you have a few "metric tons" of courage. My compliments to you.
Thanks for the kind words! But I'm afraid it's not really courage, just poverty and pride. I'm too broke to buy a newer car, and too proud to drive a Civic.
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  #21  
Old 09-08-2013, 08:16 AM
US&Germany US&Germany is offline
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Definitely can relate to that statement
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  #22  
Old 09-08-2013, 09:16 AM
First740il First740il is offline
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Re: 1998 740i misfires

Where did this whole redneck thing come from j/w.

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  #23  
Old 09-08-2013, 10:20 AM
US&Germany US&Germany is offline
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Yes, was thinking that same question too. My unqualified guess is that Florida is part of the American South and those "good ol' boys" DO possess a good degree of genius with much of their, uh, unorthodox procedures in many endeavors, including auto mechanics. Possibly with the exception of when working on an "over-engineered sausage mobile." Not my term. (Apologies. This Bimmerfest member, yours truly, IS an American with 1/4 Austrian and 1/4 Germanic "blood.")
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  #24  
Old 09-08-2013, 10:29 AM
First740il First740il is offline
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Re: 1998 740i misfires

Yeah I'm not sure you know exactly what you are talking about. I'm not a redneck, or European. But watch who you are talking about, because there is some guy in the Virginia mountains that will run circles around you in life. Watch your words my friend....

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  #25  
Old 09-08-2013, 10:39 AM
US&Germany US&Germany is offline
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I'm absolutely sure I don't know what I'm talking about. I did say it was a guess on my part, that CitizenofDreams was invoking some self-deprecating humor and was referring to himself as he himself must be the "redneck mechanic", him apparently being from Orlando Fla.
Done on my speculations. Thank you for the comment.
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