3L M54 Z4 Hesitation when accererating past 3k

M

Mitch89

Member
Hey guys,

New Z4 owner here, and I seem to have a slight issue.

I've noticed on startup what can only be described as a whoosh noise. It only happens when cold and the car has been left overnight. I also get a slight rattle when the engine turns off. Any other time (free revving, revving in gear, idling) it purrs like a kitten, no rattle.

The second issue is during acceleration. Sometimes when revving above 3000rpm the engine seems to hesitate, and sort of stutter between 4000rpm. Up to 3000rpm it is perfect, and sometimes between 3000 and 4000 it is fine too. There is no noise associated with it, the car just feels a bit jerky for a few moments, then it's fine again. It seems to mostly happen on light to mid throttle (at least that's when I've noticed it). Doesn't seem to matter if it is in "Sport" or not.

Accelerating from standstill and shifting before 3000rpm is smooth, and there are no issues when cruising at a constant speed (cruise control or not).

I've got a statutory 3 mth warranty from the dealer I purchased it from, so if it's something serious I want to get it rectified by them immediately. I've done some searching online but it's been hard to find an answer.

My Z4 and I thank you :)

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I have had something similar a couple of times in the last year.
But not the engine noises.
I will be interested to see what possible causes are suggested.
 
There are a number of things it could be. If its under warranty I would take it back to the dealer for diagnosis and repair.

Could simply be a dirty sensor somewhere. When was it last serviced?


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I get a weird 'whooop' noise occassionally, but I don't think it has happened at start-up, usually when accelerating smartly (in between slowly and hard). Thinking about it, it is quite a 'whooshy whooop', airy and reasonably quiet, seems to come from the right, behind me when it happens. Anything like that, or do I just sound madder than a bag of frogs ? :?
 
The dealer I bought it from is 900kms away so dropping by isn't an option. The last service was nearly a year ago, and the service indicator say 17000km till the next one but I'm getting it done next week at BMW.
 
Be interested if you find out what the whoosh is, hope it's not broke :thumbsup:
 
Mass Airflow Sensor can cause issues... Try a search on here and you might find something that helps?


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Well got the codes read at BMW this morning, the computer lists "DME Misfire, cylinder 2", "DME Misfire at several cylinders" and "DME Misfire, cylinder 4". The kilometres showing for these codes are literally a couple of km before I purchased the car (from a different BMW dealer).

The tech at BMW suggested a reflash might help the situation, but is concerned that could cause other problems.

Thoughts?

Rather bummed...
 
I had the same problem. Dealer changed all the coil packs. No improvement. He then re flashed the computer. Problem solved for two years. It's now back and out of warranty. I'll check with my indie and see if they can do a re flash.
 
That's what I've read from my searches on Google too, that the problem was sorted with a flash. The annoying thing is my warranty is specifically with the dealer I purchased it from (900km away), and they won't pay for the local BMW dealer to do the work. I'd be more understanding if the codes didn't show that the misfire was logged BEFORE they sold the car.
 
As a last resort could you not take the car back and ask for your money back due to breach of contract?

Not sure about the law where you live, but if the vehicle was faulty before you bought it, common sense might have a chance....


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It's possibly an option, but I'd honestly rather they just fix the problem. Other than this issue the car is immaculate, and with any luck it's a simple fix (be it a reprogram, coils, whatever). I'd also have the issue of the finance on the car, and costs associated with any withdrawal from that.

I've been exchanging emails with the dealer, will see how I go.
 
Do not get too focused on electrical problems causing misfire codes. Misfires are detected from variations of the crank speed. The cylinder number is determined by the position of the crank when the speed variation occurs. 2 & 4 are adjacent in firing order, so both codes could be from the same misfire occurring late in the cycle. Improper fuel or an air leak can also cause misfires.

One place to start would be to change the plugs, and ensuring both the high and low tension connectors of the coil packs are clean and dry. Check for air leaks. Also consider checking and maybe cleaning the injectors. If you think you might need new coils or injectors, you may get by with buying one or two and swapping them around until the problem goes away.

You might also ensure the DME connectors are clean and dry. Resort to a DME flash only if you really have no other ideas.
 
We'll the hesitation problem has been sorted by a reflash/update of the onboard computer. Revs much smoother, feels more punchy, and doesn't stutter!! Very pleased with this result.

The other problem of the noise on startup is also getting rectified tomorrow. BMW are replacing the starter motor.

Also the BMW dealer I bought it from came to the party and has paid my local BMW dealer to sort the issues out :D
 
Good news all round then - and dealers working together too... Could teach our British dealers a thing or two I think :D
 
Heh, well it took over a month of arguing about their obligations, and far too many calls to our consumer protection department, but in the end they relented. I figure they were hoping to wear me down.

Never say die!
 
Collected the car this afternoon, definitely starts quicker than it did before. Will be interesting to start it tomorrow morning!!
 
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