Engine Acceleration reduces with a mild hissing sound from engine bay
 

Hi all! This is my first post, probably on any blog ever.

Anyway I have a 2003 E53 BMW X5 4.6is. It has about 85,000 km on the odometer bt has had a brand new engine and a brand new gearbox installed only about 15,000 km ago (although about 10 years ago).

Since about 9,000 km ago, I have been noticing a phenomenon wherein the (usually great) acceleration of the engine abnormally experiences hesitation when the engine is within the RPM band of 3000 to 4000 RPM. After 4000 RPM the acceleration kind of restores itself to the usual level; however when the acceleration restores, it does so with the vehicle experiencing an abnormal sudden push (or a forward leap or a sudden step-up in acceleration). This sudden push forward feels as if the vehicle suddenly got released from something which was holding it back.

Also, about the time when the acceleration is lessened within the usual RPM band of 3000 to 4000 RPM, I can hear a 'hissss' coming from the engine bay. The sound is almost like that of an air leak.

This phenomenon initially took place in about every two or less out of 4 acceleration attempts. Now this phenomenon takes place in every 3 or more out of 4 acceleration attempts. Also, nowadays it seems to me that the overall acceleration , even in the other RPM band outside of the range of 3000 to 4000 RPM, is getting hindered. However it is to be noted that the acceleration deterioration in the other RPM band (outside of the range of 3000 to 4000 RPM) is more subtle than that within the range of the 3000 to 4000 RPM.

I will really appreciate some opinions on the matter.

Parts of that sound like a plugged exhuast and parts sounds like a fuel issue and it could even be a timing issue. You need to pull codes and do some checking and testing to find the problem.

Agreed on the checking codes. Doesn't sound like a plugged cat to me though, because that normally wouldn't present itself intermittently.

Definitely need to check the codes and live data looking for anomalies. The sound you are hearing (hisssing) doesn’t match anything similar from my 4.6 motor, but I will say the power from my engine comes on with a very noticeable “bang” around 3500 rpm. It pulls strongly before that, but really rips at and above that approximate rpm. So the hissss and power surge may be somewhat unrelated. I do have a mild tune running on my car, but other 4.6 owners tell me theirs is biased to higher rpm.p too.

Have you done a detailed visual check of the vacuum and intake plumbing? I was having odd issues with my e53 early in its new life (2002) which turned out to be the intake boot which had (very) partially slipped off the throttle. The cars are also very particular about the vacuum plumbing integrity it seems.

Dear Henn28, thank you very much for the response.

I am fully aware of the fact that the vehicle is designed as such that it rips at and above 3500 RPM and I used to love it! I am fully aware of this vehicle’s natural instincts as my family has owned this vehicle since brand new.

But, wherein at about 3500 RPM the vehicle used to level up its acceleration in a steady, confident, smooth fashion, these days it actually hesitates between 3000 and 4000 RPM and then after 4000 RPM it opens up abruptly as if it was let go of its leash.

I actually have not checked the intake boot and nor have i checked the vacuum system. Any further specific guidelines on both of these aspects will be greatly appreciated.

In the meantime, the updated fault codes are as follows:

000001
000002
00000A
000014
00001D
00003C
000062
00008C
00008D - DME: Activation, electric fan
00008D - IKE: EGS signal line disturbed
000090

Dear 80stech, thank you very much for the response.

The fault codes are as follows:

000001
000002
00000A
000014
00001D
00003C
000062
00008C
00008D - DME: Activation, electric fan
00008D - IKE: EGS signal line disturbed
000090

Hello guys, will appreciate if someone can shed some light onto my issue, especially in view of the fault codes as below:

000001
000002
00000A
000014
00001D
00003C
000062
00008C
00008D - DME: Activation, electric fan
00008D - IKE: EGS signal line disturbed
000090

Erase the codes and recheck listing what your scan tool says they are and tell us what scan tool you are using. Check all the basics (fuel,air,exhaust) first. You might even have a transmission issue the way you are describing it.

Thanks a lot for the response. I will relay your msg to my service team.

Dear BMW Patrons,

Actually since my last post, I decided to engage the dealership’s service centre to diagnose my acceleration hesitation issue.

In December 2023, I obliged the service centre to inspect the air intake system. Initially the service centre was hesitant to do so as apparently there were no related fault codes. However upon my insistence, they performed a smoke test nonetheless and indeed detected a leak in the intake manifold gaskets. [Link of video: <https://www.dropbox.com/scl/fi/y7hfd76cq1y8zzdlqeq18/Intake-Manifold-Gasket-Leak-2023-12-14.mp4?rlkey=fmvio2f8et0zll36f8ds2z9ar&dl=0>]

The gasket set replacement work was conducted in June 2024. After the repair-work there are some apparent improvements in the overall response. However my chief complain of the (intermittently occurring) acceleration hesitation between the 3000 to 4000 RPM band still persisted. It is noteworthy though that the frequency of the occurrence has somewhat reduced.

I took it back to the service centre and requested them to inspect the vacuum system, the crankcase ventilation (ccv) system, the exhaust system, and check again the air intake system.

According to the service centre:

i) there is no issue with the vacuum system

ii) they inspected the ccv system including the pcv valve and found no issue

iii) they additionally inspected the fuel pressure and found it in order [Link of picture: <https://www.dropbox.com/scl/fi/kik9memfhm96z5xn5lepw/Fuel-Pressure-2024-06-07.jpeg?rlkey=fqsmvisr2amonok50htg3whon&dl=0>]

iv) they visually inspected the exhaust system and found no issue

iv) they did another smoke test inspection of the intake system and yet again found another leak, this time on the intake manifold itself [Link of video: <https://www.dropbox.com/scl/fi/9827rjsodbdiqy4uc0jr0/Intake-Manifold-Leak-2024-06-07.mp4?rlkey=merv9ovcr3glfh6x8u592ka8p&dl=0>]

According to the service centre the leak is not major enough to result in the significant acceleration hesitation that I am intermittently experiencing. However to get closer to the ultimate solution we have decided to proceed with the repair (through replacement of the manifold). Now waiting for the part to arrive from Germany.

My one question at this point is why the fault codes do not appear even though there are evident air leaks (which I believe are altering the fuel/air mixture inside the engine)?!

I really hope the intake manifold replacement contributes to a solution of my issue. I guess I will further update this thread after the next phase. However if anyone has any opinion in the meantime, your participation will be much appreciated.

There is a lot of room for misunderstanding and misinformation in these threads where there is a third party doing the work, that being said I would really look for a different shop at this point. For example, (and I'm not saying that is for sure the problem but) "visually inspecting the exhaust" is meaningless as well as a picture of the fuel pressure gauge. Not being able to post all the codes and descriptions does not help.

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What about the Vanos solenoids? I had one stick and it gave similar symptoms but also no codes.

I've had similar symptoms with vanos solenoid (no code), broken oil fill cap (code but unrelated general performance code, and the most common culprit: cam position sensor.

When cps starts to fail it just leads or lags the actual position which opens/closes the valves at the wrong time which of course gives you bad power performance. Since it's sending a signal the computer just believes it.

I will usually confirm my suspicion of a faulty cps by charting it's angle overlap with the other bank same part. It will be subtle. It helps to have a second car to do a comparison ride.

Out of about a dozen cps failure over replaced only one tripped an error code. Usually just bad mid range torque under moderate load and weird stalling but that's on the six cylinder engines. The eights with redundant bankn will stumble but keep running.

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Been getting this PFEEWF noise underhood when shutting down, like some kind of air pressure reservoir is being purged. Also been having odd deceleration-like moments when it feel like it's decelerating despite my foot not letting up on the pedal. But it's only for a few seconds, then it's all fine. This happened once with the cruise control active at 70mph. Goosed the gas and it went away. It's not crankcase ventilation; there's no PSSSHHT on pulling the oil cap or dipstick.

2001 M54 manual.

What scan solution?

I would use foxwell to monitor the cam angles when you get this condition.

A few different things can cause them to not be the angle they should be and there are six different cam angle values that can be tracked with at least foxwell and surely others.

Cam position sensors original? OEM?

Vanos solenoids ever cleaned?

Oil weight factory spec?

I forgot if the m54 had the cage in the middle of the oil filter but I had one fail on an n52 gave similar symptoms.

How many miles? Both our M54 had the intake CPS fail at 132,000 ± 4000 miles just for reference.

The vanos never gave us any problems on either up to 190/205

I've had vanos solenoid fail on n52 at 125

I've seen oil weight mess with vanos on various engines.

No codes present. (I have an Ancel reader which is supposed to read BMW-specific codes).

Prior owner did a vanos rebuild with a kit from ECS, replaced the accelerator pedal (OEM) and DISA valve (Rein) about 20,000mi ago. His spreadsheet also has a "vanos hose" replaced about 40,000mi ago. It has 198,000 on it. No notation of cam pos sensor replacements.

Oil is 5W40 Liquimoly, Mann filter, recently changed. There is a plastic insert that goes into the filter. Now that you mention it, this started after the oil change and filter replacement... all of the prior owner's oil changes used the same oil, every 3,000mi (I have extended that to 5,000mi because $).

Can you read the cam position realtime and can you graph?

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I have no idea how to do that, but I'll see if the code reader can show me once I get the doors put back together.

Engine Acceleration reduces with a mild hissing sound from engine bay
 

I know I used the foxwell to do this. I've had similar power loss on n52 motor from the oil filter cage and from dirty vanos solenoid.

Our m54s both had CPS soft fail approximately 130,000 miles. That however presented as engine stall during slow speed throttle.

The hissing suggests CCV?

No stalling. Power seems as usual, aside from the occasional unintended deceleration blip. Some days it's fine. Once it happened with cruise control on at 70mph but only for a second or two.

CCV was replaced about 30K ago, 2019, with "PCV system w/o-rings" according to maintenance spreadsheet, along with something called "Pilot Mod to CCV" a few months later. Unsure what that means. The hiss is very brief and high-pitched, like a chirp almost, and only on shutdown. Crankcase does not appear to be under pressure if I pull the dipstick or fill cap.

Can the solenoid be cleaned? They're not cheap.

Solenoid can be cleaned. Not a difficult task YouTube will have videos how.


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