[ejloo]

Dear all,
I'd be grateful if you could help me out. Firstly, please excuse me if this post is too long winded, but it is a peculiar problem to begin with, and I've tried my best to give details as much as possible.

I have a BMW 325i 2010 LCI automatic (with N53 engine).

Problem: Intermittent poor throttle response at low rpms, EVEN in DS MODE/M mode. Started 6 months ago. No engine warning lights. Only one fault code leading to LPFP but this has been fixed and no recurrence. This only seem to come on after driving at motorway speed ( and when engine is warm.)

Scenario - after a long drive at 70-80 mph on motorway, then back into city at urban speeds, the poor throttle response at lowish RPM then occurs.

Whilst on motorway, I manage to figure out that strangely enough, the throttle response seems to be better at certain RPMs at different gear. For example, say if i'm cruising at 4th gear in M mode at 3500 rpm (or above), and press on throttle, I get that instantaneous forward response. But at same gear at any rpm below 3500rpm (say cruising at 3000rpm) and then when I floor the pedal, there will be NO response until about 1.5-2 seconds later when the car will finally pick up. This is a similar phenomenon when I'm in 3rd gear but at different rpm i.e. I get instant response at 4500rpm and above, but anything below 4500rpm and there will be a lag/delay. Same for 5th gear at 2500rpm and above, good quick response but delayed when I press on the pedal at anything below 2500rpm.

This problem happens so intermittently, there has never been any warning lights or fault codes related to the double VANOS exhaust/intake solenoids (which I have been suspecting). It never seem to happen say if I've been driving it in the city for about a week, the throttle response will be good at all RPMs. Only once I take it for a long drive on the motorway, and then return to urban/town speeds, then the problem recurs.

I've taken it to few garages (main dealer and independent) and the source of the problem has never been isolated. I did a software update, but seems fine after that because I've been driving in the city for a bit, only recurred when I drive on motorway and back into urban areas.

I'd be most grateful if you could shed some light into my rather strange, bleak problem! Like I've said, I'm aware there is some 'throttle lag' which is normal in Drive mode, but this problem occurs in DS or M mode as well.

[m20b25]

Feels a bit like something is holding it back during a lot of city driving or after a long run?

That's how mine felt before a gearbox fluid change. What's your mileage?

[SiKkBaSs]

This happened to me a lot when I first bought my 325i all them years back. Everytime I'd nail it there would be power then there would not and then there would.

This turned out to be a serious problem in the end with carbonisation of my valves. It even caused my car to completely switch off on two occasions around corners and stopping for a roundabout and at the same time locking the steering wheel as the valves "choked."

I took it to the dealers (thanks to the warranty) and they blamed it on the carbonisation due to heavy usage on the motorway and proceeded to clean it.

I noticed it as day and night when I drove it back and floored it - zero lag.

Please take this as serious and take it to the dealers and get it checked thoroughly as it is an accident waiting to happen. It is a known problem with the 325i as you can read from the below's thread.

Evidenced thread from 2009! :

http://www.e90post.com/forums/showthread.php?t=317135

[ejloo]

Originally Posted by m20b25

Feels a bit like something is holding it back during a lot of city driving or after a long run?

That's how mine felt before a gearbox fluid change. What's your mileage?

It's nearing 60K miles. Well, when I first got the car when it was around 20K miles, I was driving it for about a week and found out there was a transmission oil leak (plastic sump was found to be damaged - not sure how I did that), but it was promptly dealt with by the dealer. I cannot remember whether this poor throttle response problem was already there before the oil leak.

[ejloo]

Hi SiKkBaSs, are you referring to the solenoid valves? Or is it the intake valves? If it's a solenoid, from what I've gathered on several post, a simple clean and swap of the exhaust and inlet solenoids would suffice, if not then a replacement. But for the intake valves, it appears that some elaborated cleaning involving walnut shells is required.

Did you get any engine management light on or fault code relating to VANOS at all?

[ejloo]

m20b25 - for a good couple of years when I first got the car, I was mainly doing a lot of motorway driving.

Since 2 months ago, I've been driving in the city (at least 25 to 30 mins to work), and I've found that the problem seems to have cured itself. But, just a few days ago I drove to Cotswold (a 4 hour drive non-stop from Liverpool), and when I reached Gloucester, I shifted from D to M mode, and in 2nd gear - I tried tapping on the pedal to check the throttle response, lo and behold the problem was back! The usual nice jerky forward thrust our Bimmers are famous for was gone. Once I've restarted the engine, the problem went away, but as I drive further on for a few more minutes, the problem came back again. All throughout, there was no engine light or warning. I'm not sure if there's any fault codes logged as I don't have a portable diagnostic gadget.

It feels like something is choking some valve, as once I floor the pedal, there is near zero response, and the car only starts to 'slowly pick up' after about 2-3 seconds. Once it does, it tends to go through the whole mid to high rpm range alright.

I'm puzzled, really. After speaking to main dealer service people, and several independents, and reading up online, I can only imagine if the problem is down to VANOS solenoid (possible exhaust solenoid) or intake valves.

[themanthatcan]

Sounds to me like your gearbox adaptations need a reset. I get very similar sounding symptoms, the car seems to bog down when accellerating for a couple of seconds, more so from standing but also when moving; it feels like the car is underpowered at low RPMs and I'm trying to acellerate through treacle.

Thankfully a simple gearbox adaptation reset through INPA roughly once a month brings the car back to order; accelleration is instant as soon as I press the accelerator, there is no bogging down and the gearbox comes alive again; it's like having a new car again.

I'm planning to get the gearbox fluid changed in the near future in the hope that it's a more long-term solution, but as the adaptation reset is usually part of the process I do wonder how much of the improvements people see after their fluid changes is actually down to the reset.

[ejloo]

bump

had an oil service at the dealers (due to CBS interval). No fault codes stored in DME.
Drove away, hoping that the problem would never appear again, but it did! argh..

Has anyone of you with N53 engine had this problem before? Is it possible to get VANOS valve problem without any fault code generated? Like an occasionally sticky vanos, etc...