N52 hesitation, stuttering, jerking, surging etc

propaintballa · Post by **propaintballa** » Fri May 17, 2019 4:47 pm

So here's the video of the rattle/knock I'm talking about that makes me think this is something to do with a lifter. Obviously the overwhelming sound is the injectors, but in the background there is a lower pitch rattle/knock that seems to be more pronounced when the camera is near the left/rear of the engine. Would be interesting what others think of this...

https://www.youtube.com/watch?v=fjt2Sl9MzSk

Maddo6659 · Post by **Maddo6659** » Fri May 17, 2019 4:51 pm

Sometimes when you plant your foot theres a slight delay? I've also experienced these symptoms.

propaintballa · Post by **propaintballa** » Fri May 17, 2019 4:55 pm

Maddo6659 wrote: ↑Fri May 17, 2019 4:51 pm Sometimes when you plant your foot theres a slight delay? I've also experienced these symptoms.

Yep, to varying degrees, depending on the rpm at the time. Usually more so at lower RPM <3000.

Maddo6659 · Post by **Maddo6659** » Fri May 17, 2019 5:04 pm

Hmm. It's my intention to get my car up on the ramp and have a thorough look. I'm not mechanically minded but would like to learn. This wont happy for a few weeks however, work etc. If you learn anything, keep me informed. And vice versa from my end.

juld0zer · Post by **juld0zer** » Sat May 18, 2019 2:06 am

I would say the sound in the video is more like the early signs of a DMF failing if yours is a manual?

propaintballa · Post by **propaintballa** » Sat May 18, 2019 10:07 am

juld0zer wrote: ↑Sat May 18, 2019 2:06 am I would say the sound in the video is more like the early signs of a DMF failing if yours is a manual?

You know what, this also crossed my mind. I used to have a similar noise on my Z4 when I turned the car off without pressing the clutch down. Equally if I pressed the clutch I believe the noise went away, but I don't think this car does that.

Weirdly I have read that an unbalanced flywheel can cause misfires, or what appear to be misfires. Would certainly explain why I don't have any codes. Though not sure it can explain overall hesitation.

crhenkel · Post by **crhenkel** » Sat May 18, 2019 4:44 pm

my 2006 z4 3.0i N52 seems to have the same symptoms. rough idle at stops
N or park. hesitation on acceleration. it has new plugs and vanos solenoids. no real issues other than the hesitation and bad low searching idle rpm. I figured DISA valve so I got one on its way before I went out to look. I don't see either DISA valve unit that i thought i would find. in several online parts shops it shows the two disa valves as parts for my car. when I put in the vin the catalog. acts like they don't go in my 06 N52 engine intake.
lots i read seems to indicate often these symptoms are related to failed disa but if it is possible mine doesn't have disa valves what else is causing the symptoms.

it is an auto transmission car has 113xxx miles. starts fine drives great. accel and idle issues only. 3.0L engine. no leaks. old o2 sensors.

propaintballa · Post by **propaintballa** » Sat May 18, 2019 5:01 pm

crhenkel wrote: ↑Sat May 18, 2019 4:44 pm my 2006 z4 3.0i N52 seems to have the same symptoms. rough idle at stops
N or park. hesitation on acceleration. it has new plugs and vanos solenoids. no real issues other than the hesitation and bad low searching idle rpm. I figured DISA valve so I got one on its way before I went out to look. I don't see either DISA valve unit that i thought i would find. in several online parts shops it shows the two disa valves as parts for my car. when I put in the vin the catalog. acts like they don't go in my 06 N52 engine intake.
lots i read seems to indicate often these symptoms are related to failed disa but if it is possible mine doesn't have disa valves what else is causing the symptoms.

Be aware that you have the added variable of the auto box. In my research people have had similar symptoms before renewing the transmission fluid and filter and that kind of thing. Though that obviously doesn't explain rough idle.

As for the DISA valve, your car will have two. The 'Large DISA' is accessible and doesn't take much to remove and inspect. This thread outlines the process: viewtopic.php?t=36349

The thread instructs you to remove the intake hose to get it out... If I remember correctly, I could remove it without doing that, but that's on my e91. The 'Small DISA' is on the inside of the intake manifold and cannot be accessed without removing the intake manifold, which is an unpleasant task to say the least. As mentioned, there are two DISA valves on this engine and they are different sizes, so be aware of that when ordering. Would certainly inspect them before dropping cash into either of them. Although my Large DISA was fine, parts of the rubber on the inner DISA had torn, so I replaced that one.

Capa · Post by **Capa** » Sun May 19, 2019 12:05 pm

The lower frequency bassier 'dugga-dugga-dugga' noise feels to me, 100% like clutch thrust bearing. I have the same on mine and it does go away when the clutch is depressed.

...These engines are really starting to get on my tits...

juld0zer · Post by **juld0zer** » Sun May 19, 2019 3:38 pm

crhenkel - can you post a photo of the throttle body area of your intake manifold?

Propaintballa - what size tyres are you running and how much tread do you have left on them? Do you still experience the hesitation with DTC on (one brief press)?

propaintballa · Post by **propaintballa** » Sun May 19, 2019 4:06 pm

Capa wrote: ↑Sun May 19, 2019 12:05 pm The lower frequency bassier 'dugga-dugga-dugga' noise feels to me, 100% like clutch thrust bearing. I have the same on mine and it does go away when the clutch is depressed.

...These engines are really starting to get on my tits...

Trust me, I feel your pain xD I checked again today, and my noise in the video stays the same whether the clutch is engaged or not :/

juld0zer wrote: ↑Sun May 19, 2019 3:38 pm crhenkel - can you post a photo of the throttle body area of your intake manifold?

Propaintballa - what size tyres are you running and how much tread do you have left on them? Do you still experience the hesitation with DTC on (one brief press)?

They're staggered, 255/45/17 rear and 225/40/17 front, all runflats of same brand (pirelli). Rears are on minimum tread on the inside, others are all good. I did have the rear re-balanced when I first got the car because the car was vibrating through the seat at speed, could certainly do with the front too. As for DTC, same symptoms with it on or off.

I'm guessing you're thinking it's a traction issue, sadly this does not account for the rough idle or the surging during driving when constant throttle is applied :/ I did notice today that sometimes when I blip the throttle from idle, it drops a bit first, not every time though. I'm sure this is characteristic of a bad plug or coil. This would not make sense as they're all new, but I suppose I should re-check them at some point.

Capa · Post by **Capa** » Mon May 20, 2019 4:28 pm

It drops a bit first... Isn't that vacuum?

I'll try to get a vid of my motor, just for the sake of comparison...

propaintballa · Post by **propaintballa** » Fri May 24, 2019 10:15 am

Capa wrote: ↑Mon May 20, 2019 4:28 pm It drops a bit first... Isn't that vacuum?

I'll try to get a vid of my motor, just for the sake of comparison...

I suppose it could be... I haven't changed the valvetronic motor gasket, could need doing. Been meaning to create some kind of ghetto smoke tester to rule out a vacuum leak. What I did notice after doing my CCV was that when I removed the oil filler cap whilst the engine was running to test the vacuum, the engine would idle horribly and try to die, this did not happen before I changed the CCV, so not sure what that could indicate.

Capa · Post by **Capa** » Fri May 24, 2019 10:56 am

Yeah, I'm about there with you on that. I'm thinking some kind of oil filling syringe and a cigar is where I'm gonna go.

That's interesting to know in regards to CCV. When I take the oil cap off, there's obviously vacuum there, but the car doesn't try to martyr itself. I think changing the PCV is on the list, but given I've got an N52K it'd be a whole new rocker cover, and right now I can't really be arsed. Nor do I want to shell out £2-300 on the part.

I'm still sort of on the fence, considering whether I actually invest the money and try to fix it or go and part-ex it for something else currently. I think the noise on mine has now morphed into some kind of rattle and 'whoosh' noise between 1500-2500 rpm. Research is leading me to suspect the small DISA.

Yet more fun...

juld0zer · Post by **juld0zer** » Fri May 24, 2019 1:38 pm

Propaintballa - I came up with a theory of false traction control intervention (throttle opening restricted and injection reduced) but I would have expected the skid light to be flashing at the same time. A few days later, the theory was proven false when the juddering returned and this time it is the worst it has ever been.

Pulled and inspected all NGK spark plugs which were fitted in January, nothing really stood out. Fitted another 6 donor coils from a known good set. Even replacing the bloody tank vent valve made no change to the juddering or the negative long term fuel trims. So i'm down $200. I also made a ground strap from the rocker cover to the strut tower as the existing one is corroded. No difference.

Compared actual vs setpoint MAF at idle, 1200 and 2000rpm and it was acceptable.
Did the same with VANOS, Valvetronic eccentric shaft position, throttle body and gas pedal, all was acceptable. I didn't scope anything, so there is still a chance of a high frequency jittery signal. This was all done using values in INPA which has a somewhat slow refresh rate.

I did make a discovery that turning on the AC restored acceleration and significantly reduced the judder around 1400-1900rpm. The flat spot is significantly reduced. I can induce the juddering by turning off the AC. On my Scanguage, I am currently monitoring load, throttle position, ignition timing and intake air temp. When the judder occurs, timing is being retarded. When the flatspot peaks, load is 99 and timing is very close to zero (TDC) or negative at the worst (after TDC). Is this a sign of false knock detection?

I have bit the bullet and ordered a DMF and clutch kit......

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