random KR while cruising

05silvycrew · Post by **05silvycrew** » Tue Feb 24, 2009 1:07 pm

hey guys, been a while since I've posted anything on here. here goes...

I had my LTFTs dialed in last August, but with the colder winter months my trucks been running a little lean (+1-2 on the LTFTs)

So on a trip to see my fiance, I subtracted a little more from the injector slope to get back closer to the ideal -2-0 range. That all went fine and my LTFTs are closer back to ideal. BUT, what I also noticed was I'm getting random Knock Retard with the cruise set.

It happens when the engine gets under a little load, like when starting to climb an incline or a strong gust of wind blows right head on. the KR will jump up as high as 4 degrees, but then almost immediatly slowly fall back down to zero. it's never a long sustained amount of KR, and it's not always consistant. maybe it's always been there and I'm just now noticing.

is this normal?
if not, what could attribute to this KR?

Thanks:
Ben

Post by **mikel** » Tue Feb 24, 2009 1:10 pm

Knock under cruise?

Sounds like knock sensors going bad...

05silvycrew · Post by **05silvycrew** » Tue Feb 24, 2009 1:10 pm

sorry predator model u7193, old school with no logging capabilities.
using on an 05 silverado, 5.3, iron block

Yknhotshot · Post by **Yknhotshot** » Tue Feb 24, 2009 9:18 pm

I have also noticed this on my truck as well. Its only when on the highway going up a hill or something mine jumps to 2 then goes right back down
I have an 02 silverdao with the 5.3 aluminum block with u1798 predator.
will it hurt anything? I tried setting it back to stock and drove 50 miles then did a test and it still had the knock. Any input woud be helpful

gump2388 · Post by **gump2388** » Tue Feb 24, 2009 9:25 pm

bad gas??? or does it do it when ur using ur pedel

Yknhotshot · Post by **Yknhotshot** » Tue Feb 24, 2009 9:28 pm

mine does it with both pedal and cruise

gump2388 · Post by **gump2388** » Tue Feb 24, 2009 9:36 pm

what brand gas u running??. and what tune u have on there.

Yknhotshot · Post by **Yknhotshot** » Tue Feb 24, 2009 9:44 pm

phillips 66 91 with the diablo tune

Yknhotshot · Post by **Yknhotshot** » Tue Feb 24, 2009 9:45 pm

phillips 66 91 with the diablo tune

gump2388 · Post by **gump2388** » Tue Feb 24, 2009 9:54 pm

maybe they can shed more light tomorrow when they get in. not unless like mike said a knock sensor is going out. but its weird that its 2 different truck.

Yknhotshot · Post by **Yknhotshot** » Tue Feb 24, 2009 9:56 pm

thats what I thought

CANUCKPREDATOR · Post by **CANUCKPREDATOR** » Tue Feb 24, 2009 10:54 pm

I find my truck does the same. Low RPM, overdrive, and load will do that. I don't sweat it.

gregs · Post by **gregs** » Wed Feb 25, 2009 8:56 am

I have similar to the same problem except mine is around 1800-2300 rpm. I've cleaned the maf sensor, intake, new fuel filter, checked for vacuum leeks, etc nothings worked so far. I've been looking around recently and after doing a lot of reading on some other fourms i found out that apparently on these trucks water tends to collect on the pigtail connector of the knock sensor and ground if out, causing the sensor to send out false knock. From the way it sounds the only fix is to pull ith intake and replace both sensors $45/a piece, new upgraded wiring harness from GM $30-$60, and intake plenum gasket (dealer only don't know price yet).

now i just need to find a day when its halfway decent outside so i can get it done. No shop

Post by **mikel** » Wed Feb 25, 2009 10:44 am

Yeah, if this is happening while essentially 'lugging' the motor in high gear at low rpm, it is normal.

05silvycrew · Post by **05silvycrew** » Wed Feb 25, 2009 11:22 am

alright, i've done some researching on KR and it's causes. In what I've found, I did read about how water can get into the Knock Sensors and cause them to give out false KR readings. Other possible causes include:

1) bad gas (could be the winter blend??)
2) running too lean (which if I've dialed in my LTFT's in shouldn't be the case)
3) having a hot spot in the cylinder somewhere, pre-igniting the fuel mixture before the spark plug ignites it. causing the 2 flame fronts to collide.
4) too much timing advance (which if it was in the predator tune, would go away when the tune goes back to stock)

on a somewhat related tangent, I also read that using a lower temperature thermostat, in conjunction with lowering the electric fan threshold, can help reduce the chances of detonation by running the engine a little cooler. Sometime soon, I think I'll start a new topic on that issue...for now, I'll keep an eye on the KR.

random KR while cruising

random KR while cruising

RE: random KR while cruising