Strange Noise - Bang on 1250rpm

[nickg123]

My BMW (2001, 320ci, 2.2) is making a strange noise...

If you sit there and increase the revs slightly up to 1,250 - It makes what i can only describe as a vibration that's like having a small sub in the car, it sounds to me like a slight mis-fire or something along those lines...

Recently in Dec the car failed to start, so i took it to a garage who said the Cam timing sensors had failed - one of which had been gone for some time. They replaced both sensors and put some octane booster in as the car had been running a little Lazy you might say, and seemed quite hard to change to 2nd gear smoothly without the revs jerking slightly if that makes sense?

It was completely fine for 2-3 weeks, and i've used Super unleaded everytime when filling up to see if it would keep it going but it's pretty much back to what it was doing before, and just seems to run a bit lumpy if anything - just hard to drive smoothly.

Anyone have a clue where to start? Could it be a fuelling / Timing problem?

[nickg123]

Still hoping one of you Genius' knows :-)

[trickywoo]

Its quite likely to be another sensor problem - hopefully unrelated to the first.

Vibrations at specific revs tend to be exhaust related - possibly a loose heatshield.

Hope your luck improves.

[E21_Ross]

gotta agree with the above poster. vibration tends to be exhaust related, especially on a car which isn't exactly old. i would say check all the exhaust mounts under the car, and check they are done up ok (pref when it's not hot!)

[MitchT]

I had a vibration on my '99 318is which always seemed to occur at specific revs. Turned out to be a rusted exhaust bracket.

[E21_Ross]

MitchT said:

I had a vibration on my '99 318is which always seemed to occur at specific revs. Turned out to be a rusted exhaust bracket.

same here, on my slightly older 1982 316. all it turned out to be was it had somehow decided to lose an exhaust ring, and only appeared (the rattle i mean!) between 2-3krpm, and 4-5krpm. anything past 5k was fine, and 3-4k was fine. hope it's something simple like this!!

[nickg123]

I'm pretty sure it's going to be one of the many Sensors - it really feels like the timing is off so would suggest one of the Cam sensors has gone again....

My problem is if it is one of those same sensors again, if i just take it to the garage and leave it with them for the day, then go to collect it to be faced with a big bill it will really be a tough one to argue that they already replaced the sensor in December as how can i prove which ones they did?

I hate to assume these kind of things but in the past i've learnt to be sceptical when it comes to Garages being fair/honest so i'm just worried they'll say it was a different sensor that failed and i will have no way of knowing this or checking it?

Any advice??

Thanks for all your help so far!

[nickg123]

I still haven't taken it to the Garage yet.. guess my best bet is to call and see what they say. I just have a feeling they'll want to look at it and charge me for the privilege.