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Pr2005z4

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Will you help me solve the mystery??

2005 z4 2.5 with 125k miles. My mechanic was stumped. Rattle/vibration type noise at low rpm’s. Lasts a few seconds, then stops as rpm’s increase. May not be related but also have a smell (?) from engine compartment after running and car is hot, turned off, and I pop the hood. Also, gas mileage has decreased but car runs like new.

Thoughts???
 
had a rattle just like this. Was a heat shield under the car that had corroded around one of the fixation points. The smell. Well if its hot oil type smell these motors leak out of the rocker cover gasket. Normally towards the back of the engine. then it drops on the exhaust manifold.
 
Thanks for your replies.

Yes checked codes.

Not heat shield or cat shield.

Will note rocker cover gasket for smell — appreciate it.

Pls keep trying y’all.
 
Smell: as suggested, most likely a leaking top cover gasket, leaking oil onto the exhaust.

Rattle: have you checked all the heat shields? There are several.
If it does it at low revs are you able to get someone to stand outside the car and determine where it is coming from?
Does it do it in neutral or only in gear?
I'm assuming at that age it is the M54 engine?
If so, check the Disa valve and the Vanos assembly. With your head in the engine bay it should be easy to isolate either of these.

Increase in fuel consumption could be many things, but if we were to assume it was connected to the rattle then that too could point to the vanos unit needing new seals.
A decent diagnostic machine, including the better quality hand held ones, will show live data and you can see whether the cams are adjusting or not. If not then it means the seals are leaking and not letting oil pressure adjust the cam timing. If the seals aren't tight they can also induce a slight rattle.
 
Thanks all, this is very helpful and I’ll follow up with my tech. I am definitely a DMF so no offense taken — and I got the automotive phrasing too😉
 
Pr2005z4 said:
Thanks all, this is very helpful and I’ll follow up with my tech. I am definitely a DMF so no offense taken — and I got the automotive phrasing too😉
Click to expand...
:thumbsup:
 
My 2005 2.5i is also making a rattling or scraping noise that's driving me crazy. I've had all of the belts and the tensioner replaced, the transmission rebuilt (so it's not the torque converter), new alternator, etc. My mechanic thinks it's the catalytic converter. He says when they start to fail, the honeycomb can crack and/or chip resulting in a rattling sound. He says he's never heard this particular sound before, so he's not 100% sure.

FYI: my car does not make the rattling noise if it's in neutral on a flat surface. If I park the car on a fairly steep incline and rev the engine, it definitely makes the noise. If I park the car on a decline, or drive down a decline, it does NOT make the rattling noise.

After I've been driving the car for a while, maybe an hour or so, it barely makes the noise at all.

I'd be curious if yours rattles while parked and revving or just while moving in gear.
 
enuff_zed said:
A decent diagnostic machine, including the better quality hand held ones, will show live data and you can see whether the cams are adjusting or not. If not then it means the seals are leaking and not letting oil pressure adjust the cam timing. If the seals aren't tight they can also induce a slight rattle.
Click to expand...

Sorry to hijack thread from op,

Just interested in what you said about looking at the cams adjusting, when I rev from idle only the exhaust cam angle changes, does the inlet cam angle only change at a higher rpm, under load only or should it change just like the exhaust does as soon as the car is revved?
 
Joez4 said:
enuff_zed said:
A decent diagnostic machine, including the better quality hand held ones, will show live data and you can see whether the cams are adjusting or not. If not then it means the seals are leaking and not letting oil pressure adjust the cam timing. If the seals aren't tight they can also induce a slight rattle.
Click to expand...

Sorry to hijack thread from op,

Just interested in what you said about looking at the cams adjusting, when I rev from idle only the exhaust cam angle changes, does the inlet cam angle only change at a higher rpm, under load only or should it change just like the exhaust does as soon as the car is revved?
Click to expand...
I'd need to connect mine up and check to be certain. It's been a while.
 
Frustrating! My mystery noise/vibration seems different (low rpm’s only) but I’m going to drive it today and see if the noise occurs just revving or on incline.
 
Ok drove the 2005 z4 2.5 with 125000 miles today (automatic transmission) and heard my weird vibration noise consistently at 1600 rpm’s (stops by 2000 rpm’s). It does NOT happen in that rpm range at all if in neutral and just revving. Forgot to try on incline or decline. Thoughts or new insights with this disclosure?
 
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