Knock at low boost

[MauDeuce50]

I am getting KR at low boost. At above 45 or 50 mph, only 1 or 2 psi will cause it. At lower mph it will take a few more psi. Here are my numbers, which are all screwed up...

O2- 390-410
KR- 0.0
AF- 04-05
L8- 35-37
Bat- 13.2-13.4
Int- 128
BL- 150
Ats- 122
R- 725-800
Tps- .42
IAC- 30

I just replaced the vac lines around the turbo and charcoal canister, but it didnt help. PLEASE HELP

 

[we4Mateo]

ECM thinks you are lean or you still have a vacuum leak and actually are lean with unmetered air getting in. O2's are low, depending on how long you looked at them, and your BL is high indicating that the ecm is trying to add a LOT of fuel and apparently not getting the job done. Vacuum leak, fuel system problem, bad O2, not sure.

 

[we4Mateo]

Being lean will cause knock. Fuel filter?

 

[buickGN3:16]

are those readings at idle fully warmed up? & also downpipe or exhaust rubbing the a-arm or frame can cause the scanmaster to pickup false knock so check over those things.. Just some thoughts to consider

 

[MauDeuce50]

Being lean will cause knock. Fuel filter?

Just had gas tank cleaned, and the fuel filter and pump changed not too long ago, so maybe the injectors? I ran some techron through the system, but might have a bad one

 

[MauDeuce50]

are those readings at idle fully warmed up? & also downpipe or exhaust rubbing the a-arm or frame can cause the scanmaster to pickup false knock so check over those things.. Just some thoughts to consider

Yes they are at idle, fully warmed up, and i dont think there is any rubbing, but i will double check tomorrow

 

[3.8L V-8 eater]

Check the rest of the vac lines and double check the ones you just changed...Also have you looked at the drivers header they just about all crack and will cause your BLM's to be high....Do you have a fuel pressure gauge to tape to your windshield?? You need to verify fuel pressure is rising at a 1 to1 ratio with boost....Don't take this problem lightly!! The last guy who had a similar problem to yours with knock at partial throttle assumed it had to be false and blew his engine apart on the 1st WOT blast!!

 

[34blazer]

BLMs way too high, need to get that down to ~128, a high count indicates a lean condition

 

[MauDeuce50]

Check the rest of the vac lines and double check the ones you just changed...Also have you looked at the drivers header they just about all crack and will cause your BLM's to be high....Do you have a fuel pressure gauge to tape to your windshield?? You need to verify fuel pressure is rising at a 1 to1 ratio with boost....Don't take this problem lightly!! The last guy who had a similar problem to yours with knock at partial throttle assumed it had to be false and blew his engine apart on the 1st WOT blast!!

Ok thanks a lot, i will finish changing the vac lines and inspect the header, and no i do not have a fuel pressure gauge at all. Also ( newb question) do i need to use zip ties or something to clamp the vac hoses do you think? I used t clamps where I could but not everywhere due to accessibility restrictions

 

[MauDeuce50]

BLMs way too high, need to get that down to ~128, a high count indicates a lean condition

Right, hopefully they will go down after finishing the vac lines

 

[3.8L V-8 eater]

Ok thanks a lot, i will finish changing the vac lines and inspect the header, and no i do not have a fuel pressure gauge at all. Also ( newb question) do i need to use zip ties or something to clamp the vac hoses do you think? I used t clamps where I could but not everywhere due to accessibility restrictions

Yes I would zip tie the vac lines...When I'm at the track running the car hard I've had several blow off...Fuel pressure regulator hose even the cruise control vac hoses have blown off on me!! I now have them zip tied...If all the hoses, the header, etc check out your going to have to verify fuel pressure going up with boost..

 

[MauDeuce50]

Yes I would zip tie the vac lines...When I'm at the track running the car hard I've had several blow off...Fuel pressure regulator hose even the cruise control vac hoses have blown off on me!! I now have them zip tied...If all the hoses, the header, etc check out your going to have to verify fuel pressure going up with boost..

.
Ok thanks and sorry, but one more question: do I replace the harder vac lines( to FPR, boost gauge sensor etc...) with the soft silicone lines? Not including the hard lines directly connected to the vac block. Sorry for all the questions, but i am new and want to get everything right

 

[3.8L V-8 eater]

If you still have the harder plastic lines I would just tie those off....My fuel pressure regulator doesn't have the plastic line with the rubber boots just a piece of rubber vac line...Those boots usually will stay on but I would still put a small zip tie on them.....

 

[MauDeuce50]

If you still have the harder plastic lines I would just tie those off....My fuel pressure regulator doesn't have the plastic line with the rubber boots just a piece of rubber vac line...Those boots usually will stay on but I would still put a small zip tie on them.....

Ok thanks a million

 

[buickGN3:16]

Once blm's climb u CANNOT get them down, i have tried evrything & still running 137ish so i said "F" it!!!

 

[3.8L V-8 eater]

Once blm's climb u CANNOT get them down, i have tried evrything & still running 137ish so i said "F" it!!!

What chip do you have?? My Extender Extreme chip can be adjusted to help with getting BLM's closer to the target!!

 

[forcefed3.8's]

What are the BLMs while cruising? Idle isn't telling the whole story. When you are getting knock at 50mph, what are you doing? If you are rolling into the throttle to accelerate and it is not downshifting, it is normal, you are lugging the engine.

 

[MauDeuce50]

Once blm's climb u CANNOT get them down, i have tried evrything & still running 137ish so i said "F" it!!!

Hahaha ok, good to know, i am more worried about the knock issue at this point anyway

 

[MauDeuce50]

What are the BLMs while cruising? Idle isn't telling the whole story. When you are getting knock at 50mph, what are you doing? If you are rolling into the throttle to accelerate and it is not downshifting, it is normal, you are lugging the engine.

What are the BLMs while cruising? Idle isn't telling the whole story. When you are getting knock at 50mph, what are you doing? If you are rolling into the throttle to accelerate and it is not downshifting, it is normal, you are lugging the engine.

Ok ill let you know the BLMs cruising tomorrow. Would it help to put it in drive and try to accelerate a little?

 

[forcefed3.8's]

Drive would help pin point the problem. If it goes away, it is just from the low rpm lugging. Is your TV cable adjusted? It should want to downshift.