NEED HELP WITH KNOCK UNDER BOOST

[86DarganGN]

I have been battling a knock under boost problem (trial and error) a 1986 GN for the last two seasons. I have performed a ton of research, reading just about every knock related thread on the site. I have tried several commonsense approaches based on the information I have read with no luck, I desperately need advice, not having fun with the car!

1. First I checked, and then replaced all of the accessible vacuum hoses, at 8-10 psi of boost. Still have knock.

2. Replaced the EGR with a NAPA brand EGR, at 8-10 psi of boost. Still have knock.

3. Replaced the PVC value with a brass RJC PVC, BL reading increased from 132+/- to 160. Still have knock.

4. Caped off the vacuum tank added Lucaus Octane Booster (Is the vacuum tank really needed?) Still have knock.

5. Disconnected and caped the vacuum line to the heater control and the interior (climate control switch and vacuum lines inside the dash will not hold vacuum). Still have visual 4.6 knock in 3rd gear reading on scan master.

6. Blocked off the new EGR with a metal plate with two gaskets. Caped off the EGR solenoid, at 8 -10 lbs of boost still have visual 4.2 knock in third gear reading on scan master

7. Replaced the heated 02 sensor with a Denso 02. Still have knock at WOT. Recall display, 771mv 3.8 retard.

8. Replaced the RJC PCV value with a AutoZone brand PCV. Still have knock. The INT reading dropped from 140 to 131 and BL reading dropped from 160 to the normal, 132+/- Recall display at WOT, 820mv 2.6 retard. (Valve cover breathers soaked with engine oil).

9. Nothing is touching the knock sensor wire or rubbing the frame.

The last couple test drives I got more aggressive!

10. I tested my fuel pressure regulator. I increased the Static Fuel PSI about 10 lbs at a time until it reached 75 psi and then it jumped to 99 lbs with a half turn! The PSI held steady, it only dropped a few pounds after each adjustment. I verified my static fuel pressure again at 43-44 with the vacuum hose off and the pressure read 59-60 PSI at 15 lbs of boost on 4 strong long pulls. The knock gauge went completely red, glanced at the scan master, 4.6 visual retard but no recall!! Go figure WOT and no recall on the SM.

11. I attempted to verify the engine timing. Shorted out the ADL terminal A&B attached the timing light but the 15 degree mark is hidden by the pulley and I could not get a good enough angle to see the mark on the flywheel. Scan master recall display (733 02, 5.2 retard) at 9-11 psi of boost. The rest of my numbers stay pretty consistent. I can pictures of the spark plug if anyone is interested.
AF 05
L8 33
Int 123-131
BL 129
Clt 173
Ats 134
RPM 825-925
Tps 42
Iac 24
WOT 4.28
WOT Recall - O2 MV 789, 5.2 degrees of retard

Below, I have listed my basic setup for reference.
Bored .030 ( 3 years old, 3000 miles on rebuild)
Stock heads with new values and seats (Stock valve springs)
New pistons and rods
Polished the crank
Balanced the assembly
New oil pump
New lifters
Stock intercooler
Typical 9” cone filter air intake
New Iskey 208-208 P/N# 1194-CY cam

David Husek transmission recalibration shit kit.

Bolt on parts
3", aluminum 3 row radiator
3" SS flat flange down pipe Adjustable waste gate
3" SS test pipe
2 ¾” exhaust system
SS cross over pipe W/ new gaskets
New 42.5 lb injectors (009’s)
Adjustable fuel pressure regulator (43 psi static)
AC CR43TS, gaped at .032
Fuel pump hot wire kit
Walboro 304 fuel pump w/ basic install kit
Scanmaster 2.1
93 octane Red Armstrong Chip (F3599H)
TA 49 Turbo
Heated O2 sensor (Replaced with Denso 02)
3 bar map sensor
3” LT1 MAF
MAF Translator (3” LT1, Base setting 3, WOT setting 0)
2800 Stall convertor
Rear seat brace kit
Knock gauge and sensor
Oil pressure gauge and sensor
Temp gauge and sensor
Boost gauge and sensor
Eaton Limited slip rear diff.
30 spline moser axles
245/60/15 rear tires
S-10 front spindles, rotors and dual piston calibers
Vacuum brake booster
RJC PCV value (Replaced with AutoZone brand, BL numbers went back to 132+/-)
RJC rear motor brace

 

[SCOOBY DOO]

Post a PL file.

 

[dynoman]

Your tips voltage at WOT should be higher 4.5 + Volts

 

[Pronto]

Make sure your entire exhaust is not hitting anywhere. Jack the car up to make sure it's not rubbing on the over the axle pipe. Did you always have the knock or did it just develop?

 

[86DarganGN]

Make sure your entire exhaust is not hitting anywhere. Jack the car up to make sure it's not rubbing on the over the axle pipe. Did you always have the knock or did it just develop?

Not sure, as you can see by the mileage, I do not have much time behind the wheel. It ran strong during the engine break-in. I added vacuum breaks and the shift kit before I really had enough miles (2500) on the rebuild to go WOT!!

 

[86DarganGN]

Your tips voltage at WOT should be higher 4.5 + Volts

Thanks, I may have to install a new throttle cable, I tried adding lock-washers at the throttle pedal to take up the slack in the cable and 4.28 was all I could get without effecting the TPS setting. Will less than 4.5 WOT cause knock?

 

[86DarganGN]

Post a PL file.

Sorry, what is a PL file?

 

[Pronto]

I went to the iskey website and couldn't figure out your cam (their website sucks). You list stock springs. They may not be strong enough for that cam. Can't tell without their seat pressure specs.

 

[SHADOWII]

PL=power logger, (assuming the chip was burned for the mod's an d you cleared the ecm of any codes) It's possible the chip has become corrupted. Might try a T/T chip.
What compression ratio on the new pistons? Try closing the gap on the plugs to .028" for more consistency of spark.

 

[Pronto]

How old is the fuel filter? Have you tried raising the fuel pressure to 45?

 

[Rugby]

What is your MAF reading at WOT? I am also tracking down a knock on my car and I think I have narrowed it down to that.

 

[86DarganGN]

PL=power logger, (assuming the chip was burned for the mod's an d you cleared the ecm of any codes) It's possible the chip has become corrupted. Might try a T/T chip.
What compression ratio on the new pistons? Try closing the gap on the plugs to .028" for more consistency of spark.

I do not have a PL. I never had a check egine light or SM code. The machinist used stock replacement pistons. I will try closing the spark plug gap. If it is a chance it could be a chip, that would be sweet, a lot simpler than all the other things I have tried.

 

[Mr.Spool]

Try a 3rd gear pull rolling the throttle,does knock increase or go away?

 

[Mr.Spool]

Also needs more wot tps

 

[86DarganGN]

Try a 3rd gear pull rolling the throttle,does knock increase or go away?

3rd gear is when the knock usually starts and is the highest, I have never stay in the throttle to get to 4th gear after I see knock (limited funds)...

 

[86DarganGN]

What is your MAF reading at WOT? I am also tracking down a knock on my car and I think I have narrowed it down to that.

I do not know, I will check!

 

[86DarganGN]

How old is the fuel filter? Have you tried raising the fuel pressure to 45?

The fuel filter is new and the tank was super clean when I installed the hot wire kit.

 

[Mr.Spool]

WOT Recall - O2 MV 789, 5.2 degrees of retard

Usually when I see this the car needs more octane or needs to be a little richer.you are still low on tps I would adjust tps and iac through real race gas in the tank and try again.

 

[Pronto]

Usually when I see this the car needs more octane or needs to be a little richer.you are still low on tps I would adjust tps and iac through real race gas in the tank and try again.

And raise the fuel pressure.

 

[Mr.Spool]

And raise the fuel pressure.

I actually would leave it at 789 and see if the race gas gets rid of the knock if it doesn't or lowers the knock then I would bump it up some just to see if the change moves the car in the right direction he doesn't seem too off and red nows how to cut a chip.