[crbalch]

Hi All,

I am getting a *very* faint occasional pulse when sitting at idle. The RPM needle does not move, nor am I throwing any codes currently.

Here is the backstory: I was recently getting misfiring in cylinders 2 & 3. I took the plugs out and realized that they were gapped too large/the two were fouled. I have since replaced all of them with S55 plugs gapped to .022mm. This took care of any misfiring/codes that were thrown prior to the exchange. Everything outside of occasional idle is running absolutely flawless, and the logs I have captured do not show anything amiss (from what I can tell).

Solutions Tried:
- Half a bottle of Sea Foam put into a half tank of gas and run down to about 1/4 tank. I filled up again since then (should have run it to empty I know)
- Replaced plugs
- Ran logs at idle, and WOT...nothing seems out of place from what we can tell
- Ran diagnostics on the car - found nothing since initial codes were thrown
- Reset all adaptations using ISTA software
- Drove on the highway for about 25 minutes at varying speeds

Next Steps:
- Going to run my tank down to empty and dump a bottle of Techron Complete Fuel Cleaner into it. Will run that through and see if anything changes
- Pull a spark plug and send a picture to this thread to ensure no other red flags

I have attached a log at idle in case someone has the ability to look through and see if they can spot anything. Any additional help would be much appreciated!

[pz619]

I have something similar (faint pulse only at idle) and tied it back to the A/C. It goes away as soon as I turn off the A/C.

Maybe give that a try just in case that could be the issue.

[crbalch]

Originally Posted by pz619

I have something similar (faint pulse only at idle) and tied it back to the A/C. It goes away as soon as I turn off the A/C.

Maybe give that a try just in case that could be the issue.

When you say you tied it back to the A/C did you fix it?

[Bleeped]

Its normal when the a/c is on and very hot outside. Nothing to fix. My car has done this since day 1. Also another that I test drove.

[crbalch]

Originally Posted by Bleeped

Its normal when the a/c is on and very hot outside. Nothing to fix. My car has done this since day 1. Also another that I test drove.

What about if the AC is off?

[Taunto]

Does this happen during Cold start? Operating temp? All the time?
I am personally not a fan of Fuel system cleaners as i believe and have seen them cause more harm than good. (just my opinion).

Have you ran any sort of additive in the oil? When was ur last oil service?
The reason why i ask is because the Vanos solenoids are a common issue. They have such a very small tolerance that literally the tiniest particles can cause them to fail and sometimes you may not even get fault for them.

Also when the pulsing is happening if you slowly raise the rpm's to 2K-3K does the pulse stay constant? goes away? changes with RPM's?

[crbalch]

Originally Posted by Taunto

Does this happen during Cold start? Operating temp? All the time?
I am personally not a fan of Fuel system cleaners as i believe and have seen them cause more harm than good. (just my opinion).

Have you ran any sort of additive in the oil? When was ur last oil service?
The reason why i ask is because the Vanos solenoids are a common issue. They have such a very small tolerance that literally the tiniest particles can cause them to fail and sometimes you may not even get fault for them.

Also when the pulsing is happening if you slowly raise the rpm's to 2K-3K does the pulse stay constant? goes away? changes with RPM's?

- Operating Temp
- never run additive in oil
- have not changed the oil yet (6k miles)
- pulsing goes away as soon as I raise past the idle RPM (idling around 650)
- pulsing does not even move the needle of the RPM gauge

[Taunto]

Hmm... 6K miles is very low for vanos solenoids to start failing.... Kinda hard to diagnose and see without being there.
i feel like changing the engine oil isnt going to change anything...
How much fuel do you have left? Maybe try running Premium fuel from a different fuel station.. maybe you just happen to get a bad batch of fuel and it's trying to work its way through the system.

[pz619]

Originally Posted by crbalch

When you say you tied it back to the A/C did you fix it?

Nope. It's faint enough that I only notice at idle and generally goes away on its own. If it gets worse I may bring it to a dealer, but it's not a big enough deal for me to do so right now.

[crbalch]

Originally Posted by Taunto

Hmm... 6K miles is very low for vanos solenoids to start failing.... Kinda hard to diagnose and see without being there.
i feel like changing the engine oil isnt going to change anything...
How much fuel do you have left? Maybe try running Premium fuel from a different fuel station.. maybe you just happen to get a bad batch of fuel and it's trying to work its way through the system.

I filled my tank back up with a bit under a quarter left, so I need to run this one through and see if it fixes itself.

May still do the techron next fillup though

[reala]

Ive noticed exact same thing when ac is on.

[crbalch]

Originally Posted by Taunto

Hmm... 6K miles is very low for vanos solenoids to start failing.... Kinda hard to diagnose and see without being there.
i feel like changing the engine oil isnt going to change anything...
How much fuel do you have left? Maybe try running Premium fuel from a different fuel station.. maybe you just happen to get a bad batch of fuel and it's trying to work its way through the system.

I'm wondering my use of the word pulsing isn't quite the correct word...Maybe like a pulsing mini misfire?

Aka a misfire that is barely noticeable but occasionally there? Certainly not enough to know its there unless looking for it essentially.

[crbalch]

Taunto any chance we can maybe chalk this up to a vacuum leak somewhere? After a good amount of research I've seen quite a few people say to check for leaks. I will try to do a smoke test soon

[Taunto]

it is possible. the pcv valve is a small diaphragm inside valve cover. if you have a pressure gauge you can check that way. other than that ya smoke the intake side and look for small leak.

usually when that valve goes tho you get horrible idling and very rough running but there is a chance that it is very slightly torn.

[XutvJet]

Honest question: Are you OCD about cars?

What you're describing is pretty normal for any car, including a BMW, when the A/C and fans are on/cycling, the DME dealing with hot and humid ambient conditions, etc. Just like really cold weather, cars can tend to run a little rougher, will be louder, and sometimes make occasional funny sounds, etc. I wouldn't worry about this unless codes are getting thrown or drivability is a mess.

In hot/humid weather, my 6MT M235 is definitely down on some power and turbo lag is more prevalent. That's just the nature of driving cars in hot weather. The dual mass flywheel can rattle when I turn the car off in neutral and I can hear the throw-out bearing whirring ever so slightly when in 1st and rolling into my garage. It doesn't mean there's a problem.

[crbalch]

Originally Posted by XutvJet

Honest question: Are you OCD about cars?

What you're describing is pretty normal for any car, including a BMW, when the A/C and fans are on/cycling, the DME dealing with hot and humid ambient conditions, etc. Just like really cold weather, cars can tend to run a little rougher, will be louder, and sometimes make occasional funny sounds, etc. I wouldn't worry about this unless codes are getting thrown or drivability is a mess.

In hot/humid weather, my 6MT M235 is definitely down on some power and turbo lag is more prevalent. That's just the nature of driving cars in hot weather. The dual mass flywheel can rattle when I turn the car off in neutral and I can hear the throw-out bearing whirring ever so slightly when in 1st and rolling into my garage. It doesn't mean there's a problem.

I'm OCD about everything, but in this case the issue was not present for 6k miles, and now it is. So I am thinking that there is a problem. Therefore, I will go with recommendations people have given and things that I've researched in order to get to the bottom of it.

[XutvJet]

I really don't think your car has a problem, but if you must look......

Considering how hot it's been in the Midwest lately and the fact that you're running an intake, I'd recommend yanking it and seeing if there's a difference. It's well documented that intakes can make these cars are running odd, flakey, etc. especially in temperature extremes.

[crbalch]

Originally Posted by XutvJet

I really don't think your car has a problem, but if you must look......

Considering how hot it's been in the Midwest lately and the fact that you're running an intake, I'd recommend yanking it and seeing if there's a difference. It's well documented that intakes can make these cars are running odd, flakey, etc. especially in temperature extremes.

I appreciate your input, but you really have no idea if it has a problem considering you aren't experiencing it first hand.

As of now I have no plans on pulling the intake just yet, going to do a smoke test later tonight to see if there are any leaks anywhere first. I will clean the MAF while it is out for the test, and see what happens from there.

[reala]

Mine 16 i noticed this on the first day with 3 miles on. It doesnt bother me. Just hope this is normal on this car.

[XutvJet]

Originally Posted by crbalch

I appreciate your input, but you really have no idea if it has a problem considering you aren't experiencing it first hand.

As of now I have no plans on pulling the intake just yet, going to do a smoke test later tonight to see if there are any leaks anywhere first. I will clean the MAF while it is out for the test, and see what happens from there.

I do experience this in my M235 in excessively hot/humid conditions. My WRX did it (really bad when the A/C compressor would cycle on) and my wife's 2015 Outback 3.6R does it. My WRX would dang near stall when reversing and shifting back into 1st. It did that stock and with a tune only. It's a very common and uncorrectable OEM tuning issue. The CVT in the Outback can pulse and vibrate the chassis when going up steep grades at slow speeds and low rpms. The 6MT in my 6 month old M235 can be noisy under certain situations. Again, all normal. The point is, car's aren't perfect and they can do weird things under certain circumstances and it doesn't necessarily mean something is broken.

This "pulse" you're feeling is likely very normal as reported by myself and others and is likely the result of hot ambient conditions and A/C, cooling fan, and water pump power draw. At idle, the car is at a very low rpm and with all those systems struggling to keep the motor happy, they can create quite a power draw thus you can sometimes feel minor vibrations, pulsating, hear clicks has systems turn on/off, etc.

My car has a stock intake. I've been logging air temp vs intake air temp in the 90+ degree weather we've been having in Kansas City over the past 3 weeks or so. After about 5 minutes of stop and go traffic, air temps vs intake air temps can vary by up to 35 degrees (max of 130 degrees for intake air temps at extended idle). I would bet you $10 that your M235 with an intake is likely seeing 145-150 degree intake temps at extended idle. That will certainly make the DME work to keep the motor from detonating and can make for a groggy feeling motor. Been there, done that with many other prior cars.

[Taunto]

there are some very valuable points on both sides.
And yes it is normal for a vehicle to run slightly rough when not in optimal conditions and are normal.
That being said, If you find nothing on the smoke test and clean the maf..and the problem happens again...see if you can get a video of it happening to maybe help with the diagnosis.

[crbalch]

Originally Posted by Taunto

there are some very valuable points on both sides.
And yes it is normal for a vehicle to run slightly rough when not in optimal conditions and are normal.
That being said, If you find nothing on the smoke test and clean the maf..and the problem happens again...see if you can get a video of it happening to maybe help with the diagnosis.

True, doing both as we speak!