Timing and Detonation

[Isaiah48]

I'm having a hard time keeping it from detonating after it warms up. When it's cold, it can handle 23psi with no problem in all rpm and load ranges but when it is warmed up, it can barely handle 10psi at rpm's lower than 4,500. I also dont think it's pulling timing under detonation like I presume it should. Do I need to chip the LA3 or someting and run bigger injectors, crank up the Fuel Pressure or is the timing not adjusting as it should for some reason?

I'm going to hook up my Wide Band to see if it's getting lean and report back but I thought it might be a common issue that someone here could help me with...

The car is an 84 with 3" DP, T-3/4, External Waste Gate, Big VAM, Stinger Header, Manual Boost Cockpit boost controller, Front Mount Intercooler, 255 lph Fuel Pump, 42 psi Fuel Pressure, 35# injectors, Timing set at 12 Degrees...

[SVOeric]

VA, you guys got 91 octane premimum there, right ?

[GAboySVO]

What's the fuel pressure under boost? Is your EGR working? Knock sensor plugged in? Inline or Square intake?

[Isaiah48]

VA, you guys got 91 octane premimum there, right ?

We have 93 as well and I only use Sunoco 93 so I doubt that's the problem.

[Isaiah48]

What's the fuel pressure under boost? Is your EGR working? Knock sensor plugged in? Inline or Square intake?

I dont have a fuel pressure guage anywhere but on the Fuel rail so I cant really see what the pressure is under boost. That's good thing to look into though...

I'm pretty sure the EGR is working fine but I'll check.

Where is the Knock sensor? Everything is plugged in that i can see though.

I have the Square intake...

[Gator]

You re-pinned the harness for the LA3 ?

[Isaiah48]

You re-pinned the harness for the LA3 ?

yes and I rechecked it recently while working through another issue, good tought though...

[GAboySVO]

The knock sensor is what the EEC uses to retard timing when detonation is sensed. Its located on the back side of the lower intake facing the driver.

[BrianO]

I don't know what kind of plugs you are using, but I had several batches of motorcraft plugs that pinged with no other changes. I put in autolite 764's and the pinging is gone all together. I changed nothing else. just an idea..

[Isaiah48]

The knock sensor is what the EEC uses to retard timing when detonation is sensed. Its located on the back side of the lower intake facing the driver.

I just checked where you said it should be and that's the vacuum source for my EGR so I think I might have left the knock sensor in my old manifold when I switched over, although I dont recall anything unplugged

I also noticed that my EGR is hooked up so it's closed at high vacuum, thinking about it now, I believe it should be the other way around so it's pulling crankcase vapors until boost and then it should be closed. Right? The way I have it now it would be pressurizing the crankcase under boost making the boost slow to come on and making it leak at the dipstick and oil cap. I can smell crankcase vapor under boost now that I think about it...

This whole project has really made me go back and think about the basics...

I don't know what kind of plugs you are using, but I had several batches of motorcraft plugs that pinged with no other changes. I put in autolite 764's and the pinging is gone all together. I changed nothing else. just an idea..

I dont recall what type of plugs are in it to tell you the truth, I know I have them gapped at .029 though. I check to see what type they are...

[SVOeric]

I also noticed that my EGR is hooked up so it's closed at high vacuum, I think it should be the other way around so it's pulling crankcase vapors until boost and then it should be closed. Right? The way I have it now it would be pressurizing the crankcase under boost making the boost slow to come on and making it leak at the dipstick and oil cap. I can smell crankcase vapor under boost now that I think about it...

hu ??
The vacuum tube on the EGR should be plugged into the EGR actuator. the EGR has nothing to do with Crankcase ventilation.
PCV is for crankcase ventilation.

[Isaiah48]

hu ??
The vacuum tube on the EGR should be plugged into the EGR actuator. the EGR has nothing to do with Crankcase ventilation.
PCV is for crankcase ventilation.

Sorry, wrong accronym, I should of been saying PCV... My egr is blocked off.
Am I right about how a PCV should be hooked up though, so it is open under high vacuum?

[NavySVO]

I just checked where you said it should be and that's the vacuum source for my EGR so I think I might have left the knock sensor in my old manifold when I switched over, although I dont recall anything unplugged

Here is the location. This is a TC intake. the hole above the sensor is for an ACT.

[SVOeric]

well the PCV valve should be plugged in to the bottom of the intake. The PCV valve is just a one-way check valve.

The PCV system is not causig your issues, the blocked off EGR valve is contributing to your detonation tho.

[Isaiah48]

Here is the location. This is a TC intake. the hole above the sensor is for an ACT.

Yep that's where I put the PCV vacuum source. Now, I just need to find out where my Knock sensor is in my parts bin... Thanks for the pic!

well the PCV valve should be plugged in to the bottom of the intake. The PCV valve is just a one-way check valve.
I looked in another thread that showed where the pcv should be hooked up and I've got it totally wrong. I have mine basically like a V8 would, I have a 1" piece of hose coming out of the Valve Cover and the PCV plugged in there and running down to where I should've put my knock sensor. I also have it also reversed so that when under vacuum it is shut. I'm still just assuming that I have it backwards, nobody has confirmed that yet. I saw a pic and a comment by NavySVO that explained the set up of the PCV, thanks again Navy.
-Look on the base of the block, driver's side.
-There should be the oil separator canister there, with the outlet hose running towards the front of the car, but only for a few inches.
-It then goes verticle towards the distributor cap, where that hose should end. This is where the PCV hooks up.
-The outlet hooks up to another hose that ends up at the upper intake.


The PCV system is not causig your issues, the blocked off EGR valve is contributing to your detonation tho.

Are you sure about it not being at least part of the cause, I also saw a comment by Indiana Dave that stated that: "The PCV systems on these cars is horrible. We're all fighting blow-by.
I've got a Windstar ABS checkvalve I'm going to add to mine inline with the PCV. My PCV valve only had a couple hunder miles on it at most before it failed again... leading to a lean fuel mixture, leading to detonation, leading to a blown head gasket." This all seems to make sense to me, I could be wrong though, it seems that I've been wrong more than right lately...

Can you explain how a blocked off EGR could lead to a lean condition. I Put a solid plate to blocked off the vacuum port and then bolted back on the actuator, it's like it never existed...