[Walked U]

Backround:

I recently put my car back to stock about 2 weeks ago. When I put it back to stock I noticed that my car has been idling rough.

I did a few test on the dyno.

Before my car was idling rough I was making the following numbers :

(These numbers were all on a mustang dyno, these are weather correction numbers)

The bolt ons I had was FMIC, exhaust, and DP's

Before rough idle

-Stock boost, bolt ons, no piggy back, 96 octane. 305 rwhp / 315 wtq



After rough idle

-Stock boost, bolt ons, no piggy back, 91 octane. 267 rwhp/287 wtq

I also got a miss fire from cylinder 4. Which lead me to think that it was a spark plug, or an injector failure. I only had this CEL 1 time.

I know theres no way that a 5 octane difference would yield 38 rwhp difference on the stock DME.


Ive been talking to alot of people that have had the same symptoms as my car. They said it was their fuel pump.

I went to the dealership and had the car tested.

I did the following test :

-Leak down
-Check spark plugs
-Check injectors
-Check fault codes
-Replace fuel pump
-change oil (to check if there was any coolant or metal shavings in it)

Every test that was done came back 100% normal. I even replaced the fuel pump to make sure, and the car is still rough idling...

Now Ive been reading around seeing other people been having this problem and some people think this is normal.

My question is how many people have this problem?

My car was running perfect with the mods on the car. With no mods it started rough idling.

Starting to think that I have a vacuum leak or my coil packs are messed up.



Heres what it sounds like. Notice that the rpms dont fluctuate. I think they probably move about 50 rpms if that. Sounds like it has a mild cam... Inside the cabin it drones a bit harder sometimes also (only at certain times)




Heres the engine bay clips. All the noise is coming from the DP's back.

All revs are from 0-3k rpm.

Also note I have HFC DP's which is why you can hear the turbos a little better

[O-cha]

Wait is that clacking sound your car?

[Walked U]

Originally Posted by O-cha

Wait is that clacking sound your car?

Ya its rough idling.

[RedGT3]

Piston slap? ,Rod Knock?

[O-cha]

Originally Posted by Walked U

Ya its rough idling.

I'd say that's more than just a "rough idle" like a cylinder is not firing? I mean what did the dealer say?

[Walked U]

Originally Posted by fll335

Piston slap? Rod Knock?

Its not knock or I would hear detonation inside the cabin.

And my AFR's are at 12.2 @ redline with no piggy back

[Walked U]

Originally Posted by O-cha

I'd say that's more than just a "rough idle" like a cylinder is not firing? I mean what did the dealer say?

I have friends that work there and they did every test that was available. everything came back 100% normal.

Leak down test, checked spark plugs everything.

Sounds like a cylinder isnt firing but it doesnt make sense.

[forza1976]

just curious how come you removed your mods?

[O-cha]

Is it making that sound in the engine bay?

[Walked U]

Originally Posted by O-cha

Is it making that sound in the engine bay?

Exhaust only

[O-cha]

Originally Posted by Walked U

Exhaust only

Yea, doesn't it sound like mini backfires?

[Walked U]

Originally Posted by O-cha

Yea, doesn't it sound like mini backfires?

Almost. But Im not running rich its weird. It nudges the car a bit also, when it pops.

[O-cha]

Originally Posted by Walked U

Almost. But Im not running rich its weird. It nudges the car a bit also, when it pops.

"nudges the car"? and if a cylinder wasn't firing I don"t think it matters if your running rich. I'm no mechanic though.

[RedGT3]

Originally Posted by Walked U

Its not knock or I would hear detonation inside the cabin.

And my AFR's are at 12.2 @ redline with no piggy back

ROD Knock. bearing on crankshaft worn or damaged, caused by lack of oil. start engine if it will and pull plug wires off one at a time and you'll find out wich one. do not rev up engine too high. do not sell car to a friend. motor has to come out and extensive repair on lower end required. if you do not know what a rod bearing knock is then it is not a do it yourself fix. major repair.

[O-cha]

Originally Posted by fll335

ROD Knock. bearing on crankshaft worn or damaged, caused by lack of oil. start engine if it will and pull plug wires off one at a time and you'll find out wich one. do not rev up engine too high. do not sell car to a friend. motor has to come out and extensive repair on lower end required. if you do not know what a rod bearing knock is then it is not a do it yourself fix. major repair.

Wouldn't it make the noise in his engine bay rather then through the exhaust then?

[Park2670]

This sounds deep! Hope you find out soon Walkedu

[Walked U]

Originally Posted by fll335

ROD Knock. bearing on crankshaft worn or damaged, caused by lack of oil. start engine if it will and pull plug wires off one at a time and you'll find out wich one. do not rev up engine too high. do not sell car to a friend. motor has to come out and extensive repair on lower end required. if you do not know what a rod bearing knock is then it is not a do it yourself fix. major repair.

Im pretty sure its not rod knock because the noise goes away with varied rpms. Its only at idle.

Plus the noise is ONLY comming from the exhaust NOT the engine.

[purplewidow]

walkedU

at the end does the tach ever climb back down to 550 rpms or so?

i know you have friends at the dealer but god damn no bmw dealer on the planet should ever have let the car leave a service bay like that let alone the dealership!!!! i don't know what the problem is but that is something i know i wouldn't have messed with!!! i would take it back to the dealer and demand a regional tech to come out and look at your vehicle...you shouldn't even drive the car like that...who knows what it is you know...they will figure it out and if they don't you will get a new car out of it...there is no way they should have ever let it leave the service bay though i cannot get over that...i have friends at my dealer everyone knows me there and they would have given me a loaner right away without hesitation...i just don't understand how they could let you leave with it sounding like that...man are cali dealers that bad...i know they sell a billion bmw's but that is totally unacceptable


goodluck bro i hope they fix it for you and happy holidays sucks you have to be thinking about your baby like this!!!

[purplewidow]

damn like a lot more knowledge since i posted..maybe it's something with the resonator....is it coming from both sides or just one side?

[RedGT3]

Originally Posted by Walked U

Im pretty sure its not rod knock because the noise goes away with varied rpms. Its only at idle.

Plus the noise is ONLY comming from the exhaust NOT the engine.

OK cool. can you post the results of the leakdown test. My other idea is exhaust valve problems

[Park2670]

You must be on really good terms with your dealership? Did you pay for the fuel pump, or have it warrantied

[Walked U]

Originally Posted by purplewidow

walkedU

at the end does the tach ever climb back down to 550 rpms or so?

i know you have friends at the dealer but god damn no bmw dealer on the planet should ever have let the car leave a service bay like that let alone the dealership!!!! i don't know what the problem is but that is something i know i wouldn't have messed with!!! i would take it back to the dealer and demand a regional tech to come out and look at your vehicle...you shouldn't even drive the car like that...who knows what it is you know...they will figure it out and if they don't you will get a new car out of it...there is no way they should have ever let it leave the service bay though i cannot get over that...i have friends at my dealer everyone knows me there and they would have given me a loaner right away without hesitation...i just don't understand how they could let you leave with it sounding like that...man are cali dealers that bad...i know they sell a billion bmw's but that is totally unacceptable


goodluck bro i hope they fix it for you and happy holidays sucks you have to be thinking about your baby like this!!!

Thanks a lot man. Ya I know i stayed there for 9 hours to figure out what it was with them. Ill figure out what it is and let you guys know. I have an idea what i think it is.