I have put my tuning on hold due to bad knock at 85-100kpa. I have been running on a previous tune for 6 months without any problems, I made one 0-60mph blast getting on the highway, and this problem started. After I was on the highway I barely rolled onto the throttle 85kpa and get bad audible knock.

Since this had happened I started trying to tune out the knock. I am down from almost 30* of timing in this area, to 15 at the point where this is happening. I changed my fuel from 14:1 to 12:1 in this area. I also set up my boost timing table to pull 8* at 100kpa. This is resulting in 4* total advance before the knock begins and KR pulls the timing until it is negative. Even with 4* and 12.1AFR The truck still knocks just as hard as ever. This is under low load at ~40% tps.

One more intersting behavior. If I open the throttle fast enough to jump into boost past 3lbs, the meth kicks on and I have 0 knock. At this point, I think that it is a fuel delivery problem. I believe that the truck is actually running at the set timing, it feels like a dog everywhere since I pulled 15* out.

I thought maybe a fuel fitler, but I am still able to get 10:1 on my wideband if I command more fuel. Right now I think a few injectors may have caught enough junk at the same time that they are partially clogged. Part throttle driveability and idle is fine. The injector balance test showed very close results.

I am going to pull my injectors and have the flow checked. I sure hope to find a problem, I don't know where the next place to look would be. If anyone has had a similar experience or any advise, please post.

 

Bump for you Henry, where are you taking the injectors to have them flow checked? I'm sure you'll get it figured out.

 

Thanks Bill. I have a local friend with a flow bench, I'll have the injector results tomorrow.

 

Well, good news and bad news today. The good news is that the injectors that came with the Radix were matched extremely close. The bad news is I still have not found the problem. I am going to check a few more items today.

 

Sorry to hear your still having issues, one item (8) eliminated, on to the next. ttt for you.

 

Have you gone through a complete tank and refilled since this started? Do you have a track that sells some 104+octane fuel? If so, add 10 gallons of that to the mix and see if KR improves.

With the injectors flowing well as tested and the ability to command 10.x afr I dont see how it could be fueling. Uness your wiring harness has a loose connection and 1 or more of your injectors are not actually firing. I ran into this once.
Any misfire codes logged?

 

The wiring connections on the injectors were all tight when I removed them. I have no misfire codes. All the spark plugs look great. I re-filled my tank when this first started happening, I had about 1/4 tank left before I re-fueled. There is some unleaded race gas available around here, that would be another option to try.
I was checking out some logs I had, I am getting audible knock when running ~2000RPM and 40% tps at 70kpa. I had only 15* of timing at that point, I think that I should be able to get away with that on 87 octane although I run 91(best out here) all the time. The knock also happens when the engine is cold, low iat's, and cool weather at night.

 

I had a Audible knock when i first started tuning my 5.3... but it slowly went away... now i might get about 2.5* KR... but im still working on that. I did use a full bottle of Seafoam after i first saw that KR cause im using used 44# Injectors. but im not sure what it was.... its gone now.. and i log everytime i drive it.

Hope you get it figured out man, i know its aggraviting..

 

Still frustrated. I checked the cats thinking they might have clogged, but all looks good. I can't believe how poor the truck drives right now. I can barely hobble around town and if I have to get on the freeway its a joke because the knock is so bad that I get into negative timing and the truck won't accelerate.

 

Wow Henry, that really sucks.