jershelb

I have searched and searched for an answer to this issue, to no avail... Starting about 2 months ago, and completely out of the blue, I noticed my car began to fall on its face at about 6000 RPM. After a couple of times of this happening, I fired up the Cobb AP to take a look at the vitals. When this occurs, I am registering anywhere from 15-34 counts of knock. I 100% for sure can NOT hear spark hiss or anything of that nature, and the car pulls good and strong up until that RPM.

Can anyone offer any guidance on this? My mods are as follows Not that anything changed or is new):

AMS plumbing
AMS SRI
Catch can and CV on the PCV side
3" TBE
Cobb S2 93 OTS Map

This is driving me nuts and is VERY alarming! surely if it were REAL knock I would hear it...

Thanks in advance.

Veronica

iTrader: (2)

First thoughts...

The sensor itself is an acoustic sensor (vibrations). "Could it be" that something external broke loose (i.e. a bracket) and is just rattling against the block at 6K+ rpms?

Have you pulled the plugs and checked condition? Please post up pix if unsure of condition "goodness" or Badness...

Lastly, I would do a seafoam[tm] cleaning of the intake/engine to see if a deposit is tripping the pre-detonation.

Lastly, swap the sensor and drive/check it.

Veronica

iTrader: (2)

Oh, and you would not necessarily 'hear' the knock. it is usually has to be pretty bad to actually hear it.

If you do swap plugs - go two heat range colder to account for the tune and mods.

jershelb

I really appreciate the feedback.

I haven't had an opportunity to get the car in the air to look the engine over for broken brackets or sources of vibration, but will do that as soon as possible.

I will post pictures of the plugs. I pulled them last week and they looked like they had been burning terribly rich, so I went ahead and ordered a set of OE's. If I had known sooner I would have ordered colder plugs...

Seafoam is probably a good idea regardless. What is the preferred way to inject it in these cars?

Just so strange that it is only starting at that rpm... Makes me think it has to be something mechanical. Also, I turned the boost way down (14psi) to see if it had any impact, but the knock issue remained the same.

ikt

iTrader: (18)

replace your fuel pump relay

6000rpm=Maximum load, and the fuel pump relay has a tendency to cut out under heavy load

this would cause lack of fuel briefly,and it would fall on its face

try swapping the fuel pump relay with the headlight relay and do a pull to see if it fixes it. If it does, order the updated relay from Mits

ikt

iTrader: (18)

gotta start with the simple stuff first. Spark, air, fuel.

jershelb

No dice on the fuel pimp relay. Hoping spark plugs come today...

Thomar

Here's my opinion; before you spend any money on replacing parts, get a proper tune from a reputable tuner.

jershelb

I know that a pro tune should be in order, no doubt. What I don't want is to make the haul to the Dyno and the tuner not be able to complete it because of something mechanical causing the issue. But at the same time, they will have more in site a far as diagnosing.
If it is tuning related I'm just perplexed as to why it would just start out of the blue...
Plugs should be here tomorrow, I'll start there and will keep you guys posted!

Veronica

iTrader: (2)

^this why I didn't say tune. It started well after the tune proved itself...

Veronica

iTrader: (2)

I put seafoam through the BOV vacuum line. Easiest way, I am sure there are better ones...

jershelb

Plugs should be here today. Pulled my plugs last night and the ground and end of the threaded part are very very dark, looks like they have been burning rich. The porcelain is pretty clean though.

Important update, I free revved the car yesterday to 6500 rpm and the super knock happened. So, it did it under no boost to little load at the same rpm...

ikt

iTrader: (18)

have you tried reflashing or uninstalling/installing the map? Or calling Cobb?

jershelb

I have tried reflashing and also 3 different maps with no different results. Cobb had no clue when I called them.

Veronica

iTrader: (2)

Do the seafoam cleaning (that much soot should cleaned out). The soot indicates running rich - so leaning out and knocking is not it...