thank you. i’m going to research this. i’ve found and replaced alot of rotted rubber vacuum tubing. there’s how i got my heater and wiper pump working. what u said tho feels right as to whats going on. i’ll post later. oh and there’s no heavy black smoke.
Unfortunately that is the situation with owning older cars, rubber parts deteriorate. Vacuum hoses, coolant hoses, brake lines, and motor&transmission mounts. I would recommend proactively replacing the motor mounts, had one break on a Catalina, jammed the throttle in the wide ope position.
Another thought, replace your throttle return spring.
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It only takes one instance of a stuck open throttle to develop religion. Mine was a throttle return spring…
a motor mount did that!? thats interesting you say that because i was told i had a broken motor mount back by the tranny. i can’t tell. its nothing like other motor mounts ive broken where the engine lifts when you throttle. can you tell me a little more how that can happen? Ill check out the spring… thank you.
This is one of the issues im having, this pic isn’t my carb. but its what often comes up when i look it up. between the two idle mixture screws, the the very middle is a bigger screw that is supposed to do something to idle but cutting off air as you screw it in. but alot of the videos i find when i look up my particular carb is this pic you have. but sometimes, i find mine, but there way more info on the one you posted. if i do have that “carb idle speed adjusting screw” it is not just visible when you look at it. the only one i found like that, and in that area, is when you pull back the throttle linkage ALL THE WAY, then look under and theres the screw i circled in red in the first pic. i thought that that screw was to rise the Choke idle. someone told me that a long time ago, but i dont know anymore. you always have good info and i appreciate it Tester
Can you provide images of the carb?
Both sides and the front?
Tester
+1
The old GM recall only applied to Chevys of that era, but–quien sabe?–maybe Pontiacs were also prone to the same problem.
If the OP really wants to cheap-out on motor mount replacement, he could do what GM did, by using a bracket & cable to prevent a broken mount from causing a wide-open throttle condition. That cost GM ~$1 per car, instead of the $50 or so that it would have cost them to replace the defective mounts.
Tester i messed up and posted then deleted some pics below so i may have messed up the thread. but i believe this is my carb. i can provide pics of my actual one when i get off work. But even if its not exactly, the brass screw between the two smaller air/fuel screws are correct.
Is there anyone you know that knows their way around a carb, that you could ask to have a look at yours? It might take only a few minutes for a knowledgeable person to see what the problem is. Hard to do from here.
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I’d rather see the actual carb on the vehicle.
Tester
IIRC, that is a 2 barrel carb for the base Catalina. Bonneville’s base engine was a 389 with a 4 barrel. The only 2 barrels ona Bonneville were the three duces option.
A smoke machine is very handy for finding hidden leaks. Broke hoses, shaft bushings, failed gaskets.
You don’t need a smoke machine to find vacuum leaks.
Tester
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mine is a 4. i just posted that one to show the placement of the screws. i’ll put pics of the actual when i got off work. thanks
I don’t know where you are but in St. Paul, the back to the 50s huge car show is coming up on the 20th of June. You would likely find some helpful folks there.
As far as unintended acceleration again, I read with interest an article in the Minnesota legion paper that just came a couple days ago. Sorry, already gone to the dump. At any rate took place some months ago up by Fargo. Kid was driving a year 22 something, and the engine took off. Brakes not working, couldn’t shut off, shift to neutral etc.
The patrol finally caught up when the car was heading for gravel and a curve at about 113 mph. The patrol passed him at 135 so the kid could smash into the back of the patrol car to stop it. Computer detected the crash and slowed the car down. The state patrol blamed the computer for the situation.
The point of the article was to award the quick action of the patrolman but like you may remember, I never fully bought into th3 idea of a floor mat problem or female hysterics.
For those who have never had this happen to them, it is caused when the vehicle is accelerated quickly and the engine torques off the broken motor mount, pulling the throttle linkage, opening the carburetor wide open. The quick solution to this heart-stopping incident is to turn the engine OFF, just Off, not all the way to Lock, and it almost immediately kills the engine and the engine drops back down and you can turn the key back to On/Run. Pull off the road, clean out your shorts, and take your vehicle in and replace the motor and possibly the transmission mounts all the way around…
This is one of the reasons that manufacturers went to throttle cables replacing of the throttle linkage…
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So, im carrying on with this because i want to here your info, but i did want someone on here posted to do, and thats that i sprayed the whole thing down with PB blaster, and drove it around block and the problem seems to have went away. i had screwed in the middle screw which was supposed so lower idle, which its seems to have done, it had that pleasant glug glug glug. but after driving idle was higher when i came back and put in park. nothing like before and not very high, but it was higher. that’s normal isn’t it? i still can’t figure out what the screw is underneath the throttle linkage. its circled in red. when i got this car i found an easy blow by blow on how to tune one of these, but i spent like 3 hours looking for it online and never could again.
Yah, im on it. its good advice. i have a ramp i can pull up on and get under car to try and locate the mounts near tranny. i was told thats the one out. but its nothing like when i had one go out before. the whole engine would lift and crash down. that isn’t happening. in fact, if the mechanic hadn’t told me he thought it was broken, i dont think i would have ever known, unless it grows worse symptoms.
Okay.
Let’s see if the carburetor is operating correctly.
With the air cleaner off and the engine cold, press the gas pedal to the floor and let it up.
Now look if the choke plate is completely closed.
If it is, start the engine.
If the engine starts, look and see if the choke plate is slightly open.
If it is, rev the engine by hand and see if the choke plate opens with each rev and then goes back.
Now, let the engine run and see if the choke plate slowly fully opens.
Tester
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