Spark knock...no code

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

superdave

Proud NOOA Member
Joined
Jan 26, 2013
Messages
643
Reaction score
197
I am getting part throttle spark knock no matter what octane fuel I use in my 97 5.7. It's better with premium, but still there. I have a Black Bear Tune, and I have sent the computer back to them for a retune, but the issue is still there. I have replaced the knock sensor. Has anyone had a similar issue? I'm guessing it's either a bad EGR or a worn distributor gear, but the no CEL or code is throwing me off.
 

redfishsc

Tired of fixing lousy engineering.
Joined
Nov 7, 2016
Messages
515
Reaction score
243
Location
South Carolina
I've not had that happen before. Have you had the distributor out any recently? These Vortecs can be sensitive to cam retard, which is adjusted by turning the distributor a little, but you have to have it hooked to a scan tool to read the actual cam retard value.

Its also possible you have the wrong heat value for spark plugs. If they are too hot, they can cause the fuel to ignite prematurely
 

shamrock246

I'm Awesome
Joined
Feb 23, 2014
Messages
113
Reaction score
35
Location
Middletown De
What is the ignition advance doing when you hear knock. Are there any knock counts logged? I hear some knock towing the boat i never get a code it just logs it.
 

superdave

Proud NOOA Member
Joined
Jan 26, 2013
Messages
643
Reaction score
197
What is the ignition advance doing when you hear knock. Are there any knock counts logged? I hear some knock towing the boat i never get a code it just logs it.

I guess my next step is to check that scanning info. I would have thought that the audible spark knock would throw a code.
 

Christian Steffen

I'm Awesome
Joined
May 31, 2016
Messages
1,173
Reaction score
431
Location
Green River, WY
I guess my next step is to check that scanning info. I would have thought that the audible spark knock would throw a code.

As far as I know there aren't any codes for excessive knock retard. The pcm will happily pull the 10* (I think) max knock retard all day.

If you're already having blackbear change something, you could have him shut the egr off as a test, if you want to keep running it in the future that wouldn't probably be the best option though.
 

lxe4

OBS Enthusiast
Joined
Oct 15, 2015
Messages
66
Reaction score
30
how are your intake gaskets? my truck starts knocking on hills when it goes, then it starts to buck as the gaskets bow down further, then i start to go through oil like an old airplane. also i never get any usefull codes out of the thing. I've had the cam crank out of sync code forever, the dealer tech last year said he couldn't get it to stay stable and figured maybe time for a timing chain. the only other code I've had is O2 sensors, which i ran for years without good O2 sensors. ran way better when i finally changed them
 

superdave

Proud NOOA Member
Joined
Jan 26, 2013
Messages
643
Reaction score
197
With 206k miles on the engine, it could be a combination of several issues...I guess. It runs great. I go through about a quart of oil every 1500 miles, but part of that is minor leaks. I have thought about freshening up the engine, but I'm a "while you're at it" guy, and that will end up as a complete rebuild (I know).

I guess I was hoping somebody would say "Oh yeah, I had that and it was problem X".
 

Tom P

I'm Awesome
Joined
Jan 29, 2017
Messages
374
Reaction score
79
Location
Washington
Excessive carbon build up in the cylinders can cause a bad knock. Sounds like you're burning oil so there's a good chance your combustion chambers are pretty coked up. Pull your spark plugs to check for cylinder health. The way it was described to me was that the carbon would retain enough heat from the previous combustion cycle to pre-ignite the fuel/air mixture of the current cycle. Depending on how much buildup you have, it can reduce your combustion chamber volume as well.

Try the old "seafoam in the vacuum port" trick. Youtube it first but it will de-coke an engine real quick. I did it once on an old chevy sprint.
 

superdave

Proud NOOA Member
Joined
Jan 26, 2013
Messages
643
Reaction score
197
Excessive carbon build up in the cylinders can cause a bad knock. Sounds like you're burning oil so there's a good chance your combustion chambers are pretty coked up. Pull your spark plugs to check for cylinder health. The way it was described to me was that the carbon would retain enough heat from the previous combustion cycle to pre-ignite the fuel/air mixture of the current cycle. Depending on how much buildup you have, it can reduce your combustion chamber volume as well.

Try the old "seafoam in the vacuum port" trick. Youtube it first but it will de-coke an engine real quick. I did it once on an old chevy sprint.

I have done a Seafoam on it, but it has been about a year. Fun for the neighbors too
 

superdave

Proud NOOA Member
Joined
Jan 26, 2013
Messages
643
Reaction score
197
Excessive carbon build up in the cylinders can cause a bad knock. Sounds like you're burning oil so there's a good chance your combustion chambers are pretty coked up. Pull your spark plugs to check for cylinder health. The way it was described to me was that the carbon would retain enough heat from the previous combustion cycle to pre-ignite the fuel/air mixture of the current cycle. Depending on how much buildup you have, it can reduce your combustion chamber volume as well.

Try the old "seafoam in the vacuum port" trick. Youtube it first but it will de-coke an engine real quick. I did it once on an old chevy sprint.

Long term update. I Seafoamed it again and hammered the crap out of the truck. No more spark knock. The carbon buildup was the issue
 
Top