Knock

J

jdanna

Member
Joined
Nov 9, 2011
Hey guys - I've got an 87 GN, and i'm getting intermittent knock (car has an aftermarket knock gauge) when i get above 10psi of boost (full throttle it runs up to about 15)

This car has a really comprehensive restoration done to it, but unfortunately - i don't know exactly whats been done to the motor. The previous owner decided to keep all the service records after he got cold feet and tried to get the car back.

I've tried running fresh gas with octane booster and it doesn't seem to help. As far as i can tell, it isn't really effecting the performance of the car much - it just shows up on the little gauge.

I know i have a MAF translator installed, i dont know what heads/cams are in the engine or waht compression ratio its running.

I don't know much about these motors at all - where do i start to try and hunt this down?
I don't want to just start messing around with electronics i know nothing about...
 
Best bet is to try to find someone in your area who is good with these cars. The members here are more than generous with their knowledge and time to help. Where are you located? Post up your area and someone will chime in with help. Take it easy until you get your knock problem figured out or otherwise $$$$$$$$$. Good luck.
 
I'm in Laurel, MD

Another dumb question - i dont know if i have roller rockers or not - should i just assume i dont, and add zinc additive when i do an oil change? can it do any harm? Any reason not to just run mobil1 5w30 + the ZDDP additive?
 
If you're up for the trip, there's a MAGNA get-together in Stevensville, MD at the end of May. Bunch of knowledgeable folks who can help out.

Check the other board, or google MAGNA Buick, for more information.
 
Octane boosters raise the octane a couple hundredths of a point at the most. Do a search on here about octane boosters and you'll see the math in plain english. It basically boils down to they're a huge ripoff. You should drain your tank as low as you can and add 5 gallons of actual 110 octane race gas to see if that gets rid of your knock.
 
mearly65 said:
Octane boosters raise the octane a couple hundredths of a point at the most. Do a search on here about octane boosters and you'll see the math in plain english. It basically boils down to they're a huge ripoff. You should drain your tank as low as you can and add 5 gallons of actual 110 octane race gas to see if that gets rid of your knock.
Click to expand...
Sorry, meant to say a couple tenths of a point. I fell asleep in math class a few times.
 
I think the best i can get around here is the sunoco 94 octane stuff

I may try that on my next tank - the weather has been so crappy here the bast few days i haven't really pulled the car out of the garage

I've read about some people using LL110 aviation fuel - im down the street from an airstrip and can probably buy that more easily then i can race fuel
Any harm in trying that?
 
Oh one more thing i just remembered - the previous owner gutted the cats. could that be causing it?
 
Make sure the fuel you use is unleaded, unless you have a heated O2 sensor or are willing to change your O2 shortly. The gutted cats shouldn't hurt anything.

Using ZDDP is a good idea, unless you're sure that you don't need it. It won't hurt anything either way. The "octane booster" is worthless, and may do more harm than good. There are plenty of good articles online about those products.

How much knock are you seeing? Do you have a scan tool (ScanMaster, PowerLogger, etc)?
 
I don't have a scan tool - Im just going by a little LED knock gauge that the previous owner installed.
I don't have a scan tool yet - i plan on buying one soon.
 
OK Still no scan tool - but i pulled the ECM and it looks like it has a stock chip.
its labeled Delco BBKJ - so thats the recall chip right?

Can I get a performance chip if i dont know what cams are in the car?

Also i noticed the knock meter goes up while starting the car. Is that normal?

Im starting to worry ive done damage to the motor, but when im not in boost above like 10psi it runs great.
 
One more update - the injectors i have are part D3165BA - so 37lbs.
I don't know if that helps - im just trying to figure out exactly what i have since i dont have the records from the engine build.
 
jdanna said:
One more update - the injectors i have are part D3165BA - so 37lbs.
I don't know if that helps - im just trying to figure out exactly what i have since i dont have the records from the engine build.
Click to expand...

First thing i would do would be order a set of injectors and matching chip with a scanmaster and/or powerlogger. hard to get the car running right with no scan tool and mismatched parts. Also check your fuel pump and see if its hotwired and if its the stock pump.
 
I've emailed Eric at turbo tweak to ask about buying a chip. I'll probably buy the scanmaster from them at the same time.

Are the 37lb injectors too small? How big should i go?

Im not sure about the fuel pump but at idle its pushing about 30psi. Is that too low?
 
It is normal for the knock gauge to light up when you start the engine. It picks up the starter engaging.

Can't believe there is a ls1 maf w/translator with a stock chip? Sounds like someone switched it out.

Besides the knock gauge showing knock is the car loosing power, popping or showing any other indication something is wrong?

A scanmaster would be a good investment. The car prolly had one but went to the same place as the chip. LOL! I know that's not funny. Sorry. A scanmaster would show if the ECM was in fact retarding timing. The knock gauge is just tapped onto a wire. Not really showing if in fact the ecm is seeing knock. They are a novelty item IMO. They send more false alarms than anything.

RL
 
Looks like from your picture you put up it has a adjustable fuel regulator on it and fuel pressure when you get a tt or extender chip will need to be set 43-45psi with the vacuume line off. So take the vac line off and see wwhat the reading is.
 
It does feel like the car is loosing power - there isn't much more power from 10 to 15 psi of boost. i feel like it should pull a bit harder when it goes above 10 - its almost like it plateaus there.

im a bit worried about ordering a chip since theres a lot i dont know about the car, hopefully the guys at turbotweak can get me going - and ill buy the scanmaster at the same time.

in the meantime im driving like a grandma...
 
Are you going lean? Drops the fuel filter and make sure it's not full of junk. Definitely need to see how the a/f is.
 
86gn said:
Looks like from your picture you put up it has a adjustable fuel regulator on it and fuel pressure when you get a tt or extender chip will need to be set 43-45psi with the vacuume line off. So take the vac line off and see wwhat the reading is.
Click to expand...

OK i just went out and looked again - at idle, with the vac line on or off the fuel pressure stays around 38psi.
give it a bit of gas it drops a tiny bit. give it a bit more gas and get into the boost it goes to around 40ish.

Since its having knock i wasn't about to give it full throttle.
 
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