Rough idle after warm up. Hrmm...

[jicaino]

Wow, those numbers are a little concerning. But then again, the roughness doesn't jive with the worst cyls.
WagonsHo what's that treatment of non synt and additives? I kind of like that... even tho I always flush my engine every other oil change with LiquiMoly engine flush.

[wagons ho]

What? Don't tell me you're coming around to my way of thinking? LoL!
I'm old, so I used to go old school and put ATF in for a day before an oil change. (Used atf on a beater)
But I bought a 175k m54, that had lifter tick and 2000k to the qt oil consumption. And m54's are known for carbon buildup, but think about where/who drives them. Soccer moms and commuters.
But it ran pretty well, slightly uneven compression. (Like waters).
Walmart cheap oil and a qt of marvel mystery oil. The oil was mud brown in 1 day, 50 miles. Changed with cheap oil.
Drove 1000 miles and added marvel mystery again. Mud in one day.
Changed oil, 2000 miles, marvel mystery again, only the oil finally was just dark.
25k later, gas mileage is up from 21.5 to 26.5, I don't check oil level between changes, @(7000k). Compression is even and no lifter tick. Back to 5-30 synthetic and marvel for a day or two before changing.
Plus, as it's underpowered and I'm driving mountain passes with this car, it sees alot of 4000rpm in 4th action. So it's good and heated which helps break up carbon.

[jicaino]

What? Don't tell me you're coming around to my way of thinking? LoL!
I'm old, so I used to go old school and put ATF in for a day before an oil change. (Used atf on a beater)
But I bought a 175k m54, that had lifter tick and 2000k to the qt oil consumption. And m54's are known for carbon buildup, but think about where/who drives them. Soccer moms and commuters.
But it ran pretty well, slightly uneven compression. (Like waters).
Walmart cheap oil and a qt of marvel mystery oil. The oil was mud brown in 1 day, 50 miles. Changed with cheap oil.
Drove 1000 miles and added marvel mystery again. Mud in one day.
Changed oil, 2000 miles, marvel mystery again, only the oil finally was just dark.
25k later, gas mileage is up from 21.5 to 26.5, I don't check oil level between changes, @(7000k). Compression is even and no lifter tick. Back to 5-30 synthetic and marvel for a day or two before changing.
Plus, as it's underpowered and I'm driving mountain passes with this car, it sees alot of 4000rpm in 4th action. So it's good and heated which helps break up carbon.

Must be that I'm old and old school too. I always make sure my cars are revved up as they should. I have a 523i too so imagine how often it's revved past 4k. I used diesel before the Liquy Moly. a cup of diesel fuel mixed in the oil after warm up, let it idle and drive it light loaded and change it. or diesel and stoddard solvent, or ATF too... the point is get something with enough cleaning agents that will ungunk the several parts of the oiling system. I get antsy at the ammount of BMW that gets spun bearings or rod knocking, on good oil pumps that should outlast any older gear driven pump... now let's not get into oil talk with the millenials or we'll set things on fire

My 540i was hesitant and stumbly the other days, took it on a 600 miles road trip (300 miles, drop the wife at my mother in law's, have lunch and get back home another 300 miles) got in the car 9.30 AM and I was back by 5.20PM. That's the secret to a healthy engine that purrs like a happy kitten. Some hard loving.

[waters17]

I got a replacement DME and can access it in INPA, it's aligned properly, but now I'm getting a fuel pump relay error.

167 Output Fuel pumps-relay
Signal-/Path discontinuity current,

Signal-/Path discontinuity Initial,


For my model year, it looks like the relay is behind the dash. I've read that I can jumper the bad relay, but does anyone know if I can temporarily swap it with one of the relays in the trunk? I think they're all the same.

[AusE39er]

I can't seem to get the software working again, so I can't do another diagnostic. In the meantime, does anyone have any experience with an issue similar to mine?

Lol I know that feeling for sure. When I saw your photo there I was like "wow, a working DIS". When it works it's feature rich next to inpa, but that's when it works.

[whiteghost1]

Hi Waters or Reggieleemorton - I am experiencing the exact same warm or hot idle issues + throttle opening stumble as you:

1. idles butter smooth when cold, but after 1+ mins of running it starts to idle rough (but steady)
2. when cracking open the throttle at idle, the engine stumbles for a split second and you hear the woosh of air - after that split second stumble, the engine generally revs smooth and strong
3. intake smoke test shows no vacuum leaks
4. if I'm in a high gear/low cruising RPM scenario and I punch it, I do notice a slight stumble/misfire for a 1-2 seconds, then it smoothens out and pulls to redline - this happens intermittently, and is more noticeable in the higher gears
5. engine pulls hard at WOT in gears 1-3, but almost feels like it lacks the same "punch" in gears 4-6
6. whenever I transition from cruise to a full vacuum scenario (like quickly releasing the throttle) I get a small exhaust pop/backfire.....every time
7. also, when pulling up to a stoplight, clutch in and I come to a stop - the engine stumbles for a second and the RPM dips, then it stabilizes to a rough idle
8. the only codes I get are P0136 & P0156 codes (o2 secondary sensor circuit - bank 1 & bank 2 respectively) - what's weird is I consistently get these 2x codes simultaneously, and not one at a time

I'm at a bit of a loss on what could be the cause without any detailed diagnostic software. Any thoughts on what this could be?

[waters17]

I don't know, man. Your symptoms sound almost exactly like mine. Unmetered air is my issue, and I've pretty much given up on trying to find out what's causing the problem. I'm pretty sure my cats paid the price for my negligence, so if you are concerned about the health of your cats, you should get it fixed soon.

I get an intermittent CEL light for the tank vent valve, which I've replaced, so I'm wondering if it might be an electrical issue. Not sure if it's related to the idle condition.

The weird delays your getting with throttle response is related to the air/fuel mix and the computer trying to compensate.

[R Shaffner]

Smoke test. Of both the intake and the crankcase.

[waters17]

I just ran out and did another smoke test on mine. If I blow smoke into the dipstick tube the only place it comes out is the intake box. I blocked the intake box and smoke doesn't come out anywhere.

[JimLev]

Andy, what’s the best cigar brand to use for this test?

[waters17]

LOL I don't know! I'm using a paint can and mineral oil.

[jicaino]

Andy, what’s the best cigar brand to use for this test?

Let's qask Good Ole Billy C. in Arkansas

[R Shaffner]

I just ran out and did another smoke test on mine. If I blow smoke into the dipstick tube the only place it comes out is the intake box. I blocked the intake box and smoke doesn't come out anywhere.

I'd still smoke test the intake directly. And check to see if any part of the intake is loose. If so it might leak just when vibrating, when the engine is running. Also, since you put smoke in the dipstick tube, examine the dipstick it to make sure it isn't the problem.

When the engine is idling, remove the dipstick. Does the idle speed change? With your finger over the hole, can you tell that it's trying to pull air into the tube?

[R Shaffner]

Hi Waters or Reggieleemorton - I am experiencing the exact same warm or hot idle issues + throttle opening stumble as you:

1. idles butter smooth when cold, but after 1+ mins of running it starts to idle rough (but steady)
2. when cracking open the throttle at idle, the engine stumbles for a split second and you hear the woosh of air - after that split second stumble, the engine generally revs smooth and strong
3. intake smoke test shows no vacuum leaks
4. if I'm in a high gear/low cruising RPM scenario and I punch it, I do notice a slight stumble/misfire for a 1-2 seconds, then it smoothens out and pulls to redline - this happens intermittently, and is more noticeable in the higher gears
5. engine pulls hard at WOT in gears 1-3, but almost feels like it lacks the same "punch" in gears 4-6
6. whenever I transition from cruise to a full vacuum scenario (like quickly releasing the throttle) I get a small exhaust pop/backfire.....every time
7. also, when pulling up to a stoplight, clutch in and I come to a stop - the engine stumbles for a second and the RPM dips, then it stabilizes to a rough idle
8. the only codes I get are P0136 & P0156 codes (o2 secondary sensor circuit - bank 1 & bank 2 respectively) - what's weird is I consistently get these 2x codes simultaneously, and not one at a time

I'm at a bit of a loss on what could be the cause without any detailed diagnostic software. Any thoughts on what this could be?

Is this on an early 540? If so, check/clean the ICV.

For me, hesitation at lower rpm in a taller gear has been a good sign that one or more coil packs is going bad. (It's harder to create a good spark when the mixture is richer.) If you have INPA, look at the roughness screen. It might point you to the cylinder(s) with the weaker coil pack(s).

[waters17]

I'd still smoke test the intake directly. And check to see if any part of the intake is loose. If so it might leak just when vibrating, when the engine is running. Also, since you put smoke in the dipstick tube, examine the dipstick it to make sure it isn't the problem.

When the engine is idling, remove the dipstick. Does the idle speed change? With your finger over the hole, can you tell that it's trying to pull air into the tube?

Yeah, all that stuff is fine.

Andy, what’s the best cigar brand to use for this test?

I got to thinking about this later. Was that a Scotty Kilmer reference?

[whiteghost1]

Is this on an early 540? If so, check/clean the ICV.

For me, hesitation at lower rpm in a taller gear has been a good sign that one or more coil packs is going bad. (It's harder to create a good spark when the mixture is richer.) If you have INPA, look at the roughness screen. It might point you to the cylinder(s) with the weaker coil pack(s).

My coils have always been suspect as they are the originals as far as I can tell. Will swap in a new coil one cylinder at a time (as I don't have INPA) and see if anything changes.

[R Shaffner]

My coils have always been suspect as they are the originals as far as I can tell. Will swap in a new coil one cylinder at a time (as I don't have INPA) and see if anything changes.

I've done that too.

[boeing747]

LOL I don't know! I'm using a paint can and mineral oil.

Hello, did you change maf? I have the same problem in 325i coupe no vanos. When cold, fine, but when hot, the idle is unstable. It's definitely a fuel/air mixture problem. Have you tried another chip?

[waters17]

Hello, did you change maf? I have the same problem in 325i coupe no vanos. When cold, fine, but when hot, the idle is unstable. It's definitely a fuel/air mixture problem. Have you tried another chip?

Another chip?

I was never able to resolve the issue. I'm certain that the issue has completely destroyed one or both of my cats, though.

[jicaino]

I'm having a similar scenario, suspecting a vaccuum leak but find none. In the meantime I replaced the TB with a newer one from a N62 and the car changed day and night. Butter idle, no hesitation or bog on acceleration, throttle response is supreme on all ranges, and it picked up some inches/hg at idle. It's like a totally different animal. I never noticed such a difference with just a "minor" element in the intake replaced, or any other tuneup/wear item replacement, and I did swap all coils at one point, etc etc etc. The difference this TB has made is huge. Larger than when I removed the cats. Who'd knew.

[KeysCoupe]

Which car did you swap the N62 TB onto, your 540?

[jicaino]

Which car did you swap the N62 TB onto, your 540?

yes, sorry I didn't clarify.

[waters17]

I'm having a similar scenario, suspecting a vaccuum leak but find none. In the meantime I replaced the TB with a newer one from a N62 and the car changed day and night. Butter idle, no hesitation or bog on acceleration, throttle response is supreme on all ranges, and it picked up some inches/hg at idle. It's like a totally different animal. I never noticed such a difference with just a "minor" element in the intake replaced, or any other tuneup/wear item replacement, and I did swap all coils at one point, etc etc etc. The difference this TB has made is huge. Larger than when I removed the cats. Who'd knew.

Interesting... I've been thinking about doing this from time to time. Fantastic reason to do so!

[jicaino]

Interesting... I've been thinking about doing this from time to time. Fantastic reason to do so!

Do it! the car feels like a new car. Smooth, supreme throttle response in all range, almost flawless transition, it makes such a great difference that I almost cannot believe it. I certainly would take my praises with a grain of salt, had I haven't had the chance of actually experience it myself.

[waters17]

I've only done tiny bits of research into the tb upgrade. Is that something that will function without a call to DudMD?