Bad Knock

[GogglesPisano]

Ok Guys,
Here It Is, Havent Driven The Gn A Lot Since Thanksgiving, And Now That I'm Driving It More I Noticed That If I Cruise Her Nice, And Step On The Gas Moderately It Takes Off Real Fast, If I Really Jump On The Pedal I Get This Horrendus Detonation Complete With Marble Sounds From The Motor. Definitley A Little Concerned! Any Advice?
Fred

 

[Boost231]

dont jump on the gas anymore till you figure it out. if you can hear it detonating i can only imagin how your motor feels.

 

[GogglesPisano]

thanks very much boost231. i can drive the car, and give it moderate acceleration, and even jump on it slightly, but when i get into it fully, thats when it knocks bad. its still quick, but i cant reach its full potential with that knock going on. need to find out why it happens.

 

[my85grandnation]

I had the same problem with my 85 GN that I dont hardly ever drrive except to shows in the summer time. What happened was that over the time of sitting I think the injectors or just the upper part of the intake got gummed up a bit and that caused the knock. How old is your gas, and what octane is it? What I would do is go find your best quality gas in your area. Here it is Shell and it works really good on gummed up stuff because of the additives it has in it helps clean the engine as it burns. Put in a full tank of good gas that is high octane say 93 if that is what you can get. You also want to go to GM and get a cleaner that is called Top Engine Cleaner.. I know it comes in spray form to spray thru the throttle body while the car is running, but it may also come in a bottle to pour in your tank. You can also try auto parts stores and ask for products made by BG. They make an upper engine cleaner that you spray thru the throttle body and it works great, and also use their 44K which is an in tank treatment. I would do that and then after that tankful of gas, just fill up again with any good high octane and then go drive and carefully listen for knock, and I would also suggest getting a knock gauge just to be safe. I HTH. Dusty

 

[alb84]

Do you have a fuel pressure gauge? It might be time for a new fuel pump. You need to be able to watch the fuel pressure when you boost it. As the boost goes up, if the fuel pressure goes down you will have a huge knock. Also you need to be sure that it is not over boosting. An after market boost guage helps here. There are alot of things that could make it knock, but those are a couple that are on the top of the list to try first. Later
Danny

 

[chrisgarrett]

Pisano,
Do not go into boost until you figure out what is wrong. If you can hear the detonation, you are killing your engine. You will surely blow the headgaskets. Please stop driving until you sort this out.

 

[alb84]

I certainly don't mean to go out and beat on it. To find out what is wrong you need to perform tests. Do not go out and try to find out what is wrong by analizing the pitch of the knock. Testing should reveal where the problem lies without having to hear that nast knocking sound at all.
Danny

 

[BRAD_PADGETT]

ALB84- I have spoken with Googles and he is running a stock 85. He is limited by the 85 ECM and the lack of a knock gauge or a scan tool. At this point if I was Googles -Park the car until you make some upgrades because you are headed for a blown head gasket. The real bottom line is that all 84-87 Buick as well as 89 TTA cars will have to switch to the LS1-MAFtranslator, and the 87 ECM and chip. They do not make any new MAF for these cars anymore and the remans do not work. Just a couple of cents. Brad

 

[GogglesPisano]

To All Who Replied:
I Have Listened To All Advice That All Of You Have Given Me And Have Taken It To Heart. I Have No Intention, Nor Do I Want To Grenade My Motor. I'm Actually Going To Take The Gn Up To Cottons Performance In Agawam,ma And Let Jack Cotton Figure This One Out. I'll Load It On A Car Trailer And And Tow It Up With The Suburban To Him. I Have Had My Gn Since 1995. And It Has Been Great, But My True At Area Of Expertise Lies In Vintage Cadillacs. I Have A 64 Fleetwood That I Can Disassemble And Reassemble Blindfolded. I Never Bothered To Dive Into The Gn's Operational Aspect Of Turbo Chargers And Sensor Driven Ecms. I Maintained The Gn With Regular Dealership Servicing With A Dealership That Has A Mechanic That Owns 4 Turbo Gn's And T-types, So He Is Familiar With The Car Thankfully. I'll Post A New Response When I Nail Down A Reason For Why This Is Occuring, And Brad, Your "2 Cents" Is Always Welcomed As All Input From All Of You More Knowledgeable Power 6 Owners.
Humbly,
Fred

 

[alb84]

I have had at least one 84, and most of the time 2 since 1989. I am semi retired now for a little over a year. In my performance shop I did mostly diagnosis of computer related drivability problems. I don't know all there is to know about it by any stretch of the imagination, but I do know a few things about diagnosing a GN. I would have to say that most of the guys that have a question about what might be wrong with their GN are wanting help and information to repair it themselves, and I am happy to try to help. I have yet to blow up a engine doing the tests it takes to diagnose a problem, but I probably will one of these days. The ECU on the 84-85's is very capable of safely controlling the funtions needed to make 5-600 HP. If/when my maf dies I think getting rid of the maf all together is what should happen with one of the several piggy backs available to initiate such a change. I am sure Cottons will have no problem takeing care of what is going on with your car, but if you wanted to spend the money on a few gauges you could take care of it yourself with the wealth of information available on this site. Either way I am sure you will be back on the road in no time. Later
Danny

 

[GogglesPisano]

Thanks Alb84,
I'm Sure I Could Too. Just Not Too Sure If I Have The Energy To Deal With It. Its Easier For Me To Be Lazy, And Say "here Jack You Fix It And I'll Pay You." Right Now I Have 1964 Cadillac Fleetwood That Needs To Be Put Back Together Before The Cadillac Lasalle Clubs National Driving Tour 6/20-6/25, And I Still Have A Little Way To Go. Right Now The Caddy Has To Take 1st Priority.
Fred

 

[alb84]

It looks like you have your work cut out for you. I am no good at making a interior look good. I bet that thing is a kick to cruise in. Good luck, I hope you get it done in time. What motor does that have in it? Looks like it is going to be a beauty.Later
Danny

 

[GogglesPisano]

cadillac

dan,
really all i have to do is paint the floor with eastwoods rust encapsulator, lay down the new rugs i have , and then reinstall the front seat that i had reupholstered. everything else is just oil change and tune-up. two pumps of the gas pedal and she fires right up. it has a 429 v-8. runs great, no smoking, ticking or knocking, and doesnt burn or drip oil. it was my uncles original caddy and was in sacramento until his death in 2002. then i inherited it and had it shipped to ny. she drives "like a cadillac". i get a lot of looks, and thumbs up when i drive it. even the power door locks still work well. don't get me wrong, i love my gn, but this caddy is a part of family history. it was born the same year as me.
fred