17 year old with a 1984 Bonneville Brougham!

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md5underground
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Joined: Tue Mar 31, 2015 12:21 am
Year and Trim: 1984 Pontiac Bonneville Brougham
128k
5.0 V8 305

17 year old with a 1984 Bonneville Brougham!

Post by md5underground »

Hey Y'all! Today I became a Bonneville owner! I went about 20 miles outside my town and bought this bad boy for $360. It had a few problems obviously, That's why I am here actually. Here, I'll a make a list

Idles REALLY high, No tach so I'm guessing 2500-3000rpm
Since it idles really high, it accelerates by itself. I was cruising down the highway at 55 without even touching the pedal. It will accelerate and stay there by itself, a bit scary

Smokes, Smells like when you start a car that's been sitting. Gassy. Bluish smoke :banghead:

Check engine light is on, don't know how to clear that. Brake light is on also, I've checked the fluid and is fine?

When it sits overnight, leaks oil out of valve cover (Gasket, I know how to do that)

That's pretty much it. I bought it from an old timer that SWORE it had 128k. Looking at the interior, I believe him. Arizona sun absolutely trashed the exterior paint and plastics, surprisingly the rag-top is in great condition. Engine is DIRTY. Caked on old oil and dirt, really want to know if it's okay to power wash the engine. The little town I bought it in had nothing but dirt roads, so I guess that's what it's from. The A/C obviously doesn't work. The vents blow hot air even when it's on fresh air.

Any useful info here? Also it seemed to burn an entire half tank of gas in only 20 miles?!?! Thats almost 3 mpg isn't it?

Thanks for helping a newbie.
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KM AXer
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by KM AXer »

Welcome!
Post some photos when you can.

Starting with the basics... Yea you can powerwash the engine. I always put plastic bags over the electrics, like the alternator and distributor/coils before doing so, and avoid spraying those. But it will help you find the source of leaks.

I'm not familiar with the generation of cars like yours, but the idle... That is bad, and dangerous. You can begin by checking to see whether the throttle body closes completely, of is sticking open. Vacuum leaks don't usually get the idle so high, but a big one might...

For the brake light, the thing which first comes to mind is that the parking brake pedal is not coming all of the way back when released, or the switch for it is not adjusted properly. Check that.

It was a while ago, but I remember being 17, and the first car..... Educational, for sure. Study it, look for information, and figure out how to repair. Even us old guys are still learning.
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nos4blood70
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by nos4blood70 »

Welcome to the forums fellow youngster.

Basically what was said above.. You can spray the engine to your heart's content, just avoid directly spraying the alternator and other electrical bits.
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by ddalder »

I had a 1982 Pontiac Pariesienne (well actually two of them over the years) which in Canada was the same as the US Bonneville. Absolutely great cars! I'm wondering if someone has adjusted the idle RPM on the carb? The first car I had was "fixed" by the selling dealer (a Ford dealer that didn't want to fix the problem properly). This was to compensate for a hesitation on acceleration from a stop. All they did was crank up the idle RPM to about 1,200 so there was no more hesitation. I never had to press the gas either to get moving. There are two areas on the base of the carb that wear over time allowing air in which affects the mixture. The fix was to bore out the holes and press in some bushings for the throttle shaft. You may also want to seriously consider a carb rebuild kit. Adjusting carbs can sometimes be a little tricky though so you may or may not want to tackle it on your own, depending on your skill and comfort level.

The valve covers were a notorious problem. There are better gaskets available now but the originals were made of cork. GM at one time also made available some retainers that fit under the bolts. They were about 4 inches wide and helped to more evenly and over a larger surface area apply pressure to the cover. Since the stock covers are a thin metal they would bend and warp under the pressure of the bolt alone promoting leaks.
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by dadofone2011 »

Welcome to the club, I have no knowledge of this car so I'll let the others fill you in.
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CMNTMXR57
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by CMNTMXR57 »

md5underground wrote:Hey Y'all! Today I became a Bonneville owner! I went about 20 miles outside my town and bought this bad boy for $360. It had a few problems obviously, That's why I am here actually. Here, I'll a make a list

Idles REALLY high, No tach so I'm guessing 2500-3000rpm
Since it idles really high, it accelerates by itself. I was cruising down the highway at 55 without even touching the pedal. It will accelerate and stay there by itself, a bit scary

Smokes, Smells like when you start a car that's been sitting. Gassy. Bluish smoke :banghead:

Check engine light is on, don't know how to clear that. Brake light is on also, I've checked the fluid and is fine?

When it sits overnight, leaks oil out of valve cover (Gasket, I know how to do that)

That's pretty much it. I bought it from an old timer that SWORE it had 128k. Looking at the interior, I believe him. Arizona sun absolutely trashed the exterior paint and plastics, surprisingly the rag-top is in great condition. Engine is DIRTY. Caked on old oil and dirt, really want to know if it's okay to power wash the engine. The little town I bought it in had nothing but dirt roads, so I guess that's what it's from. The A/C obviously doesn't work. The vents blow hot air even when it's on fresh air.

Any useful info here? Also it seemed to burn an entire half tank of gas in only 20 miles?!?! Thats almost 3 mpg isn't it?

Thanks for helping a newbie.
Ahh, the great 301...

1) the smoking. That've the oil leaking from the valve covers you later mention, they dripping onto the exhaust manifolds.

2) Check engine light on. Too many things it could be. Hard to diagnose over the intertubes and you probably won't get any codes out of it. Probably EVAP related.

3) Brake light on. Fluid can be fine, probably low. Probably because they're wore, and that's telling you that they're wore, triggering the switch.

4) Oil leaking overnight. well, you have figured out it's the valve covers tighten them to spec. It will probably fix issue #1
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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2011 Camaro SS
2009 Pontiac G8 GT: L76, Sport Red Metallic
2004 GMC Sierra 2500HD: Victory Red - 8.1L Big Block and Allison
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... RIP
1999 Chevrolet Suburban: Sunset Gold Metallic - RIP
dalder
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by dalder »

The Canadian equivalent (Parisienne) from 1982-86 had the 5.0L small block 305 in most cases, a few had a 3.8L 231 cu in. engine but were very uncommon...
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CMNTMXR57
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Re: 17 year old with a 1984 Bonneville Brougham!

Post by CMNTMXR57 »

Sorry, didn't catch that he had 305 in the avatar area. :)
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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2011 Camaro SS
2009 Pontiac G8 GT: L76, Sport Red Metallic
2004 GMC Sierra 2500HD: Victory Red - 8.1L Big Block and Allison
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... RIP
1999 Chevrolet Suburban: Sunset Gold Metallic - RIP
md5underground
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Posts: 2
Joined: Tue Mar 31, 2015 12:21 am
Year and Trim: 1984 Pontiac Bonneville Brougham
128k
5.0 V8 305

Re: 17 year old with a 1984 Bonneville Brougham!

Post by md5underground »

https://www.youtube.com/watch?v=CmTjL42K0kE

Unlisted video showing the weird ignition setup and how high it idles. Also how bad it smokes. Any ideas?
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