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Discussion Starter · #1 · (Edited)
Hello fellow members,

This is my first post. Thank you for reading and replying in advance.

My 2003 E39 540i has this strange issue: it experiences low rpm rough idle when the car has a cold start in the morning and outside temp is "cold" (40-50°F in the SF bay area). Here are more details:

1) Right after start, RPM is about 800; and everything is fine.
2) Then, engine temperature starts picking up, but still in the blue area.
3) After 1-2 minutes, RPM starts dropping, and the car starts shuddering slightly.
4) Then, RPM drops to about 300, right on the thin line on tachometer (I guess that is the lowest allowed RPM before stall). Shacking becomes very noticeable.
5) When RPM is about 300, and engine temperature is still low, engine runs very smoothly if I press the gas pedal, and push RPM to 800. Shuddering returns if the pedal is released. I also can hear some sound which is like rubber sheets hit each other whenever the gas pedal is released.
6) 10 minutes after the cold start, once engine temperature meter dial settles, no more shacking, or rubber hitting sound.

After my mechanic replaced vacuum/intake hoses, brake boost vacuum, VANOS seals, the car run smoothly for a couple of day; and then shuddering returns as the same.

I think the issue is related to low temperature, maybe fuel system? Also, maybe things (such as hose, O-ring) were tightened by the mechanic; but became loose again after a couple of days' driving.

Any thoughts? Thx!
 

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It needs to be scanned with a BMW specific scanner. There are codes in these cars that generic scanners won't pick up. You also need to read live data such as fuel trims to rule out vacuum leaks etc...
 

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I have the exact same issue with my 540iT. I replaced all the plugs and a few of the coils, it was coding a misfire, definitely less of an issue now but it's still there. My mechanic mentioned that it might be an oil issue so that's the next thing we're going to look into.

I'll post if we manage to solve it.
 

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On both cases, like brandon said fuel trims are huge here. since both these cars don't have ICV it really boils down to fuel trims right fast. Since neither are reporting they cant drive the car fuel is out as a possibility. The next logical place to go is 02 and fuel trims.. cant move forward until we have those.. smart phone, torque, elm327- 20 bucks and you can have a great way to look at fuel trims..

then watch this vid. for general understanding and knowledge

https://www.youtube.com/watch?v=5WnM_NsOtd8
 

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Discussion Starter · #9 ·
On both cases, like brandon said fuel trims are huge here. since both these cars don't have ICV it really boils down to fuel trims right fast. Since neither are reporting they cant drive the car fuel is out as a possibility. The next logical place to go is 02 and fuel trims.. cant move forward until we have those.. smart phone, torque, elm327- 20 bucks and you can have a great way to look at fuel trims..

then watch this vid. for general understanding and knowledge

https://www.youtube.com/watch?v=5WnM_NsOtd8
Very helpful. Will bring it to the shop on Thursday. Will keep you guys posted.
 

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....so here's the thing.
I cleared the LTFT to zero.

I drove with the scanner following the profile from 0% to 5% to 8.4%

and I heard the Jetson's Car this AM in the cold 32F morning. So maybe the CCV is pushing just a little.

The Bank 2 did approach 10% but then backed iff to 7%
and the car ran fine then till I got home.


Maybe the CCV
 

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Ok just remember trims is the addition of BOTH short and long.
 

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Ok just remember trims is the addition of BOTH short and long.
As I get comfortable navigating the screens for mixture and oxygen sensors I see the values for Banc One and bank to have an additive and multiplicative mixture adaptation. The multiplicative is in percent, and it went up to 3, 8 then to 10. I'm assuming this is LTFT.

The additive value is a decimal. 0.21. In ms. Milliseconds?

Anyway, point being the % figure never gets over 10- then settles back to 6 or 8% as the car warms up. 10% IIRC is within acceptable ranges- tho maybe on high end. I'm focusing on CCV for now, and looking for the other telltale signs.
 

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bigmphan you're crossing over on vgdti thread.. start up a new one makes it less confusing.. AND...additive is not ms... but % always %.. correct on Multiplicative.. start up a new thread and i"ll explain the rest.. you're crossing terms and understanding
 

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bigmphan you're crossing over on vgdti thread.. start up a new one makes it less confusing.. AND...additive is not ms... but % always %.. correct on Multiplicative.. start up a new thread and i"ll explain the rest.. you're crossing terms and understanding
Dammit- and I watched both halves of that Fuel Trim video, too.
Plus the one on MAFs. The guy is good- and puts a lot of the garbage rumbling around my brain into perspective.

Thanks for the input: My thread is here: http://www.bimmerfest.com/forums/showthread.php?t=893982&highlight=

Along with the new stuff I found while reading my datastream!
 

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Discussion Starter · #15 ·
Update:

I got the car back. The mechanic said he fixed a couple of vacuum leaks. However, this morning it still shudders although not that hard. And, it stalled before a stop sign; idle RPM is very low, at 300. When it dipped lower, it stalled. So, I do not think it has been completely fixed.

BTW, anybody knows good shops in SF peninsula area (San Mateo county)? I have to look for new ones...
 

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did he tell you all that he did or replaced?
 

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Discussion Starter · #17 ·
He pointed to two hoses: one in front, close to cooling fan; and one close to cabin. I really lost confidence on the shop after many years' good experience. I think they are closing the business.
 

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It always mystifies me when I hear about shops replacing parts without attempting a definitive diagnosis. What the heck do they have the diagnostic equipment for, anyway? A good shop should be able to analyze fuel trim numbers and explain clearly what they mean. In any event, just on the basis of the symptoms lasting only until the car warms up, my guess would be a vacuum leak. Did the shop ever do a smoke test?
 

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Discussion Starter · #19 ·
He was so confident, said he saw such issues many times, and did not do a smoke test. I agree on this: "In any event, just on the basis of the symptoms lasting only until the car warms up, my guess would be a vacuum leak." Moreover, its idle RPM is too low at 300, which eventually leads to stalling, even when the car is warm. Have to move on to another shop.
 

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Discussion Starter · #20 ·
Updates:

Switched to a new shop. Here are faults codes and fixes:
"retrieve fault codes & found 140 map cooling,
026, 028, 027, 029 mixture adaptation multiplicative and adaptive limit reached B1&2,
050, 051, 062 cylinder misfires,
114 cam sensor B2 open signal,
smoked tested intake, replaced leading manifold gasket at throttle motor"

Got the car back yesterday; it run fine this morning. I'll see how it goes.
 
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