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1995 Cadillac Fleetwood Brougham
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Discussion Starter · #1 ·
Hello folks. I'm having a problem with my daily driver, which is a 1984 Buick Lesabre with an Olds 307 motor (carb'd). I had owned the car for a couple weeks and it hadn't given me a single problem. Then, I was on my way to a concert and it was the first time I had taken the car on the interstate since I had bought it. As soon as I got up to cruising speed (about 65 mph) the car started jerking violently. The best way I could describe it would be like if you were to slam the gas pedal to the floor, then let off, then slam it to the floor, then let off, over and over again. The car also makes noises when this is happening, it sounds like it is misfiring or starved for fuel (like the way a car sounds right before it runs out of gas). And as this continues to happen, my speed keeps dropping and dropping until the car won't go more than 25-30 mph and I had to drive on the shoulder with my hazards on. A few times, I was able to get the problem to cease by stopping entirely, putting the car in park, then accelerating again and putting the cruise control on. This only worked a couple times, though... the rest of my attempts, the cruise control made no difference.

On the way home from the concert (after the car sat for 6+ hours) the problem was even worse. The car died 4 times on the way home (acting as if it was starved for fuel). After I got sick of this happening, I decided to exit the interstate and take regular roads all the way home, and it ran and drove fine the whole way home.

Ever since this episode, the car has had problems with cold starting. When I let it sit overnight, the first time I try to crank it in the morning, the car fires right up and then dies. Then I try to start it again, and I have to keep pumping the gas to get it to start, but it always starts on the second try. Then, it runs really rough for the first 30-60 seconds of driving (hesitating and just running rough in general). Then after that, it runs totally fine around town and it starts perfectly for the rest of the day. It's only when I let it sit for a day or two that it has this problem starting.

I haven't seen a single dummy light come on during any of this, so I'm totally lost. People have suggested many different things to me, from the cats to the fuel pump... and I have no idea what the problem is. I haven't taken it on the highway since that first time and it's been getting me around town with no problems.

Any input is appreciated! It would be nice if I could figure out what the problem is and fix it before the car leaves me stranded (which of course always happens at the worst possible time). Thanks everyone!
 

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It could be the floats, or a general carb rebuild. It also could be your choke. I have not messed with carbs for a long time. Check your fuel filter, and fuel pump too. If it has a distrubutor with pionts, they are a weak point. Another thing you can check is the ignition wires, etc.
 

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Discussion Starter · #3 ·
It could be the floats, or a general carb rebuild. It also could be your choke. I have not messed with carbs for a long time. Check your fuel filter, and fuel pump too. If it has a distrubutor with pionts, they are a weak point. Another thing you can check is the ignition wires, etc.
What are "floats"? I should also mention that the car supposedly just had a tune-up and I know it has brand new fuel lines (so I would assume they changed the fuel filter too, but I'll double-check).
 

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First car was an '87 Cutlass Supreme with the 307ci carb'd boat anchor.

Had the same issue over the winter, turned out to be a clogged cat.
 

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Discussion Starter · #5 ·
First car was an '87 Cutlass Supreme with the 307ci carb'd boat anchor.

Had the same issue over the winter, turned out to be a clogged cat.
Thanks. If that is the issue, I'm assuming you can't "un-clog" the cat, right? You just need to replace it? Or I could just delete it, since I don't need to pass emissions.
 

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Does a clogged cat explain the poor starting? Delete the cats if you want, it should be cheap to weld in some pipe to delete them. But I'm thinking your fuel pump, carb, wires, plugs, or distributor are at fault. Sounds like electrical to me, something that your higher rpm driving made worse, like arcing in the distributor or a dieing fuel pump. It's easy to pull a few plugs to see how they look, do a visual of the wires, etc.
 

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What are "floats"? I should also mention that the car supposedly just had a tune-up and I know it has brand new fuel lines (so I would assume they changed the fuel filter too, but I'll double-check).
Carbs have reserviors in them to allow the fuel to cover the jets. The venturi effect "pulls" fuel from the reserviors. To keep the reserviors at the correct level, they use a check valve and a float to monitor fuel level in the chamber. Replacing them is sometimes part of the carb rebuild. Upon reflection, if it runs around town, but not on the highway, it is either fuel starvation, malfunctioning automatic choke, or ignition. The starting scenerio leads me to the choke.
 

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Discussion Starter · #9 ·
Carbs have reserviors in them to allow the fuel to cover the jets. The venturi effect "pulls" fuel from the reserviors. To keep the reserviors at the correct level, they use a check valve and a float to monitor fuel level in the chamber. Replacing them is sometimes part of the carb rebuild. Upon reflection, if it runs around town, but not on the highway, it is either fuel starvation, malfunctioning automatic choke, or ignition. The starting scenerio leads me to the choke.
FWIW, I'm told the car has a manual choke. Not sure if that changes anything.

Your not gonna see too many dummy lights on somthing that old.... What if you take it up to high RPMS in park/neutral?
I will try this in a little bit and see what happens, but I think it will probably be no problem. I have revved it up pretty good in park when I was starting it and it didn't do anything weird. Although I didn't get it up near redline or anything.
 

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Discussion Starter · #10 ·
I will try this in a little bit and see what happens, but I think it will probably be no problem. I have revved it up pretty good in park when I was starting it and it didn't do anything weird. Although I didn't get it up near redline or anything.
When revving the car up near redline in park, everything appears normal. It seems to be a speed issue rather than an RPM issue by itself.
 

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Not nessarily a speed issue, but more likely a load issue. Reving a motor is easy, putting a load on it and reving (ie: moving the car down the freeway) is where your problems show up. Sounds like its starving for fuel, and only getting fuel to a couple of cyclinders during load at speed. Burnt down my mustang motor by repetedly driving it with this exact same issue. I got a batch of bad gass that clogged up my carb, and it wasnt spraying fuel correctly, and kinda just dopping it straight down into the middle two cyclinders in each bank.

Pull the carb and have it rebuilt, it wont hurt to have it done anyway.
 

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Discussion Starter · #13 ·
Put your foot on the brake hard and put it in to drive. Then give it some throttle and if it starts bucking then its not getting the right fuel to air ratio.
Not sure what this accomplishes. It doesn't matter how much gas I give it, the problem still only occurs above say 60-70 mph. I could drive around town at WOT doing burnouts all over the place and it would give me no problems.
 

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Been a long time since I worked on a carb. It should have a fuel filter in the fuel line inlet to the carb; little tiny filter about the diameter of a dime and about two inches long. On the blazer I used to have, whenever that filter got dirty, the motor ran like crap. I would replace that and run some carb cleaner down the primaries (or if it's a 2BBL, I guess that would be "primary") and see if its any better. If not, then it may be time for a rebuild.
 

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Discussion Starter · #16 · (Edited)
Alright... just to update this...

The problem gradually got worse (started happening at lower and lower speeds, until the car became undriveable). Now, the car will start but dies immediately.

Any thoughts? Thanks.
 

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Alright... just to update this...

The problem gradually got worse (started happening at lower and lower speeds, until the car became undriveable). Now, the car will start but dies immediately.

Any thoughts? Thanks.
+1 on carb tune-up or rebuild.
 

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Discussion Starter · #18 ·
+1 on carb tune-up or rebuild.
That's the way I'm leaning as well. I figure it has to be either the carb or the fuel pump. Here is another question...

I have a brand new Holley 600 that I bought for my 2nd gen Camaro (which has a Chevy 350). I'm wondering if I can use this carb on an Olds 307? I know they are both 4-barrels. That would be ideal, since it would be both free and an upgrade, and money is tight.
 

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I should also mention that the car supposedly just had a tune-up and I know it has brand new fuel lines (so I would assume they changed the fuel filter too, but I'll double-check).
So...what did the mechanic say he did?
If he sent a bunch of crap up your fuel line that carb needs to be opened up
 

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That's the way I'm leaning as well. I figure it has to be either the carb or the fuel pump. Here is another question...

I have a brand new Holley 600 that I bought for my 2nd gen Camaro (which has a Chevy 350). I'm wondering if I can use this carb on an Olds 307? I know they are both 4-barrels. That would be ideal, since it would be both free and an upgrade, and money is tight.
If it bolts up, put it on. You will know almost immediately if the carb is the problem. It sounds like the carb.
 
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