thumping noise on cold starts

cwarren · 12-11-2012, 07:25 PM

so for the last three days when i get in and start the car first thing in the morning i get this thumping noise . car starts idles for about 30 sec and then thump,thump,thump,thump,thump.... then sound is gone . and will not do it agian all day . first time it happen i thought someone was beating on the side of my car its that loud ...

any ideas of what this could be or has anyone had this happen to them .

thanks in advance !!

E93Blackhawk · 12-12-2012, 04:24 AM

Same thing happened to me was jerking and vibrating sort of. Turned out in the end to be the 02 sensors.

Possibly making the fuel pump run double as hard or not hard enough so it jerks is my guess.

Get it down to the dealer n get him to check for codes

Jeff@TopGearSolutions · 12-12-2012, 11:44 AM

Hard to say....

Could be leaky fuel injectors, or a HPFP or LPFP on the fritz.

Could be misfires from spark plugs.

Could be o2 sensors.

Check for shadow codes and regular codes or wait till it persists to throw a CEL.

If you have enough mileage on the car 35K+ it could even be time for a intake valve cleaning.

cwarren · 12-12-2012, 10:42 PM

Ok guy so i feel alittle stupid .i got the chance this morning to lift hood and start car to see what the hell was going on. turns out the thumping noise was my hsf4 kit trying to prime itself or somthing (not sure ) this kit is new to me for 2 months or so ran bms kit before. never had this issue till now and only thing i can think of is i ran tank low about two weeks ago to make sure failsafes where working correctly.guess i bleed system tomarrow and see if it resolves the problem . whats funny is how loud it sounds inside the car . i never would have guessed this if i did not see it for myself,,,,,
thanks guys .

12-11-2012, 07:25 PM	#1
cwarren Captain 82 Rep 725 Posts Drives: 08 e92 Join Date: Jan 2012 Location: portland iTrader: (1)	thumping noise on cold starts so for the last three days when i get in and start the car first thing in the morning i get this thumping noise . car starts idles for about 30 sec and then thump,thump,thump,thump,thump.... then sound is gone . and will not do it agian all day . first time it happen i thought someone was beating on the side of my car its that loud ... any ideas of what this could be or has anyone had this happen to them . thanks in advance !!
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12-12-2012, 04:24 AM	#2
E93Blackhawk First Lieutenant 31 Rep 344 Posts Drives: 2008 335i M sport Join Date: Oct 2011 Location: London iTrader: (0)	Same thing happened to me was jerking and vibrating sort of. Turned out in the end to be the 02 sensors. Possibly making the fuel pump run double as hard or not hard enough so it jerks is my guess. Get it down to the dealer n get him to check for codes
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12-12-2012, 11:44 AM	#3
Jeff@TopGearSolutions 3441 Rep 79,212 Posts Drives: C6 Z06, 09 335i, 10 335xi Join Date: Dec 2008 Location: www.TopGearSolutions.com iTrader: (37)	Hard to say.... Could be leaky fuel injectors, or a HPFP or LPFP on the fritz. Could be misfires from spark plugs. Could be o2 sensors. Check for shadow codes and regular codes or wait till it persists to throw a CEL. If you have enough mileage on the car 35K+ it could even be time for a intake valve cleaning.
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12-12-2012, 10:42 PM	#4
cwarren Captain 82 Rep 725 Posts Drives: 08 e92 Join Date: Jan 2012 Location: portland iTrader: (1)	Ok guy so i feel alittle stupid .i got the chance this morning to lift hood and start car to see what the hell was going on. turns out the thumping noise was my hsf4 kit trying to prime itself or somthing (not sure ) this kit is new to me for 2 months or so ran bms kit before. never had this issue till now and only thing i can think of is i ran tank low about two weeks ago to make sure failsafes where working correctly.guess i bleed system tomarrow and see if it resolves the problem . whats funny is how loud it sounds inside the car . i never would have guessed this if i did not see it for myself,,,,, thanks guys .
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