Engine Detonation (Help)

[85supreme]

I need some help determining possible causes for detonation that is occurring.

I have an 87 GN and when I bought the car it was completely stock except for the air filter and exhaust. I hooked up a scan master and noticed that I could never go past 3/4 throttle without the scan master showing some knock. (Max 12.9 deg) So i tried not build any boost while I was driving.

NOW,
I just got done installing a walbro pump w/ hotwire kit, 42lb injectors W/ matched chip and an adjustable FPR all from turbo tweak. I also installed the RJC power plate hoping that all of this would fix my original problem.

Took it for a ride after setting the fuel pressure to 43lbs with the line off which dropped to 39lbs with the line on. Was able to go WOT until about around 50 mph and then you could hear it start to detonate all of a sudden. Got off the gas asap. Scanmaster showed 19.9 degrees.

I use Sunoco 93 and the chip is programmed for 93 as well as matched with the new injectors. Don't really have any of the other scan master readings but can get them. Just let me know which readings are needed. Any tips or help solving this problem would be great. I don't plan to be racing this car or doing that much more modifying, but need it to run 100%

Thanks!
-Mike

 

[SCOOBY DOO]

Let 'er warm up in Park...and post your SM readings.

 

[MauDeuce50]

I am chasing a similar problem... Maybe check your motor mounts and make sure exhaust isn't hitting anything.

 

[85supreme]

The pinging could be clearly heard for those brief moments. I should have mentioned that, but I think its safe to rule out false knock

 

[MauDeuce50]

The pinging could be clearly heard for those brief moments. I should have mentioned that, but I think its safe to rule out false knock

Ohh ok

 

[85supreme]

Just went out and got these readings

02 115-700
AF 05
L8 35-38
BAT 13.6
Int 128
BL 125
CLT 170
ATS 104
TPS .50 (idling) .48 (key on) 4.40 (key on WOT)
IAC 36
MAL 00

 

[SCOOBY DOO]

Do you have a fuel pressure gauge hose you can place under the windshield wiper to verify fuel pressure is rising 1 to 1 with boost.

 

[85supreme]

I have a fuel pressure gauge, but no REAL boost gauge. And I have a digital dash so that pretty much tells me nothing. Is a boost gauge and making sure the fp is rising 1:1 my next step?

 

[Raeban]

I would set the TPS to 0.42V key on engine off. Also, check to make sure your boost hose is hooked up to the solenoid.

 

[85supreme]

Went out and set the TPS to .42 and found that boost hose going to the solenoid was half missing. Put all new hoses on and the problem seems to be fixed. When I took it for a ride I didn't exactly go WOT, but was close. No pinging, no knock on SM. Thanks for all your help guys!

 

[Raeban]

Glad you got it fixed.

 

[Razor]

You need a boost gauge on the car ASAP. What was happening is you where over boosting the car for the octane you had in the tank. Too much boost and not enough octane=knock. Be glad you didn't grenade the head gaskets on the motor.
At least you had the scan master telling you there was an issue.
TPS was the only thing off. Numbers above .46 the computer thinks your foot is on the throttle. Thats why adjusting below it fixes that. .38-.46 is the normal range.

 

[85supreme]

Thanks. One of my next purchases will be a few gauges for the car. I just haven't gotten around to everything because Im away at school so I only spend the summers driving it. And when i do its my daily so i try not to beat on it anyway.