Exhaust note

[carbloke]

Recently bought a Z3 3.0i. The only problem I have found, if it is really a fault at all, is that there appears to be a "hole in the exhaust" sound. It's that pop-pop-pop sound. I've checked the exhaust underneath. No problems showing. Someone mentioned throttle body failure of some kind. No more on it from the garage owner as it would cost! Any thoughts on this would be gratefully accepted.

[lightning]

You mean a sound it makes on the over-run?

My 3.0 makes a similar noise, but never when driving along, just when slowing down in gear.

[Alan W]

I get that 'pop' from the exhaust on my 2.8 if I blip the throttle when it is cold?

Also, if I start it from cold and just leave it running in the drive just ticking over after about three or four minutes the engine will cut out? Starts again straight away and then no more issues.. any ideas anyone?

[Davejue1]

My 2.8 also pops when i let the revs off, I just thought it was the exhaust but some on here will tell you it's over fuelling. But it runs perfectly, doesn't cut out and fuel economy is where it should be so I don't mind it. It's part of the characteristics for me.

Cheers
Dave

[Mike Fishwick]

Some after-market siencers have this effect, but otherwise look for a small air leak.

Leaving a cold engine to idel for three of four minutes is a dreadful thing to do - the engine will be running rich and slow, a lot of unburnt fuel gathering in the combuistion chamber and fouling the spark plugs until the engine cuts out. The rest of the fuel will wash oil off the bores, and pass the rings to contaminate the oil

[Alan W]

You are right about not leaving car running Mick but I have never owned a car that has done this ie cuts out if left to idle from cold for three of four minutes so I am wondering if this is an indication of a fault or how about this .. maybe there is a fault and the car is running too rich on start up and the EMS is working out that there is too much fuel around and switching her off to prevent damage to the engine / fuel wastage? Drive her away from cold and there is no issue, just if left ticking over.

[Southernboy]

I must query the "over-run" idea...When driving, if you remove your foot off the accelerator and with the gear engaged, there is absolutely no fuel being supplied to the motor... so the suggestion of fuel causing the popping is incorrect. It's part of the fuel economy thing which is common to most vehicles... ie. if you put the car into neutral at speed and "freewheel", it is using fuel to maintain the idle, if you keep it in gear, the fuel supply is cut off until the revs reach idle speed when the fuel is then allowed to pass to the motor. The popping when decelerating in gear may have more to do with unburnt fuel in the exhaust system which ignites given the increase in oxygen together with the minimal fuel... anyone with any actual knowledge of the phenomena might enlighten us on that ??

[Mad Max]

The 3.0 sport I had pop'd and burbled like a good 'un. It's meant to, it's tuned to do that. It's a sporty sound. I actually miss it on the MC as all you've got is rasp!