Vibration with tune under load

[Ihave1]

any updates on this? I brought my car into the dealership and they told me they would not investigate further due to my kw suspension but that its not a normal vibration. Who else has this problem and is lowered? Could it be due to the driveshaft angle? It still happens even when I flash back to stock.

[KingOfJericho]

It is carbon buildup. I had the same thing and it took the dealer nearly two weeks to figure it out but as is common with other direct ignition vehicles, carbon buildup is going to be a common and ongoing issue. It is unrelated to you KW suspension and that should be obvious if they take a test drive with you.

[Ihave1]

When it was happening with you did it feel like the vibration was in your seat? It definitely feels like the rear end is shaking but I know vibrations can feel like they are coming from places nowhere near where they originate.

[KingOfJericho]

Mine felt like it was originating in the engine bay and felt like it was misfiring. It was under load in higher gears.

[icabod7]

KingofJericho,

Would the problem go away if you downshifted and got to higher RPMs? I am surprisingly having the opposite problem. I get a high pitched fast oscillating rattle when I hit mid-to higher RPMs in most any gear (but especially pronounced in 1st through 3rd gear). The sound goes away if I upshift and the RPMs drop back down.

Thoughts?

[KingOfJericho]

Definitely not carbon buildup. The buildup is mostly in high load situations at low RPMs.

[Ihave1]

Sometime in the next couple weeks I am going to take off the intake manifold and clean the carbon buildup. I have 44k miles and doubt the previous owners ever cleaned it out. I will report back on if it helps or not. If it doesn't help I think it has to be the flex disc, center bearing, or drive shaft u-joints. We'll see. Hopefully its just the buildup because my idle sometimes is rough too.

[Ihave1]

Spent the past few nights cleaning out the carbon from the intake valves. Took it for a spin and it's like driving a new car. The difference before and after is almost as noticeable as before and after a tune. Its crazy. Thanks KingOfJericho

[Rafstar]

Is There Any Particular Product I Can Use To Clean Intake Or You Really Have To Take Off Intake Manifold To Clean It Manualy

[icabod7]

Originally Posted by Ihave1

Spent the past few nights cleaning out the carbon from the intake valves. Took it for a spin and it's like driving a new car. The difference before and after is almost as noticeable as before and after a tune. Its crazy. Thanks KingOfJericho

Just as an update, when I flashed to the newest version of Cobb Stage 1 Aggressive v401 beta the oscillation/vibration went away completely.

As for the carbon build-up I recognize it will be an ongoing issue. Ihave1 could you describe your technique for cleaning the carbon deposits? How products did you use? How long did it take?

[Ihave1]

I followed this guide
http://www.n54tech.com/forums/showthread.php?t=12258

I used a combination of brake parts cleaner and carb cleaner with a gun cleaning brush and dental picks. The hardest part was getting some of the connectors off and getting the pistons to TDC, but it was not too difficult overall. I probably spent 1 hr per set of valves so 6 hours total plus assembly and disassembly. I think if I had let them sit longer with the cleaning fluid it would have gone faster overall. To get the valves to close I put the car in first or second gear and grabbed onto the spokes on the rear tires to rock it back and forth like it says in that guide. I didnt have a socket that would fit on the crankshaft.

Rafstar I dont think anything besides physical abrasion would get much of the carbon off. It's like when you burn sugar in the bottom of a pot. Hard as a rock. Some people do sea foam through the vacuum line from the DV's.

[sbrauns]

sorry to reply to this old thread. But I recently installed a JB4 and I too have this strange vibrating sound. It really sounds like something is not right. Did anybody ever found what it was? I understand that romak47 was able to solve it by removing the sound generator from the charge pipe. Anybody else has this same experience? What is the best way to remove the sound generator. Will need something to plug it.
Thanks.

[Cozy]

This noise/vibration from the rear of the car that you can feel through the floor and seat when flooring it at 2000rpm+ in a high gear with a tune is due to heavy load on on the engine/transmission/diff. You are requesting the car to produce 400lb-ft or torque at revs where the car cannot accelerate fast enough to cope with the power. This does not happen with a stock tune as you simply aren't producing enough torque, period to load the mechanical components enough.

Take it easy on your car, if you want to pick up a little speed on the freeway or while cruising in town then just increase pedal travel a little. If you want to go balls out then drop from 6th - 4th, 5th - 3rd or 4th - 2nd and get moving. The car will thank you for it as I cannot imagine what, if any, damage long term abuse like this could cause to your transmission and besides, cars love to be revved once in a while so wind it up through the gears properly.

For reference I trialled this with Cobb on my 335i and 135i and the vibration happens on both.

[sbrauns]

Thanks for the clear explanation JamJay!