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I took my car for a spin earlier today and after maybe 15 minutes of driving, it all of a sudden started jerking so I pulled over. I shut the car off, let it sit for a little, and then I pull back into traffic. A short time later it happens again and this time the car decides to shut off as well. My grandfather said it could be vaporlocking or there’s something up with the carburetor. (This isn’t the first time it’s happened either. It also happened the day after I bought it). I’m not a car person so I have no idea. I was hoping someone might have a solution. Thanks!
There are lots of kinds of jerking - side to side when the brakes are not right, acceleration when the carb is off, clunks when the suspension bushings aren’t working right. And on…
If it’s carb-related in your view, I’d suggestion you switch out the fuel filter(s) first. Then test it. There may be one or more filters. I have one between my tank & fuel pump & another between my pump and quadrajet carb. If that doesn’t fix your issue, consider replacing the fuel pump.
If that doesn’t work, one thing to try would be rebuilding the carb. Factory was the Pre-qjet 4 barrel, I think it was called the 4GC. I don’t know much about these, but refreshing the gaskets shoudl help. However if your carb throttle plate is leaky or not snug, it may need bushings to stop vacuum leaks or straightening in case it’s warped.
Anyway a few reasonably inexpensive things to chase before it gets really engine-expensive-ugly….
I agree with Chris (cfair). You need to be more descriptive if you want accurate help over the net. Think of it like walking into a parts store and saying to the counter person "I need a part".
Do you have even basic old-school car skills? Do you know someone with this skill set? Can you find someone with this skill set?
We recommend getting some manuals for it if you plan on keeping it. Body Chassis etc. For engine trans & chassis look for a Chilton or Motors manuals and there are specific manuals for 65s. Google. Some of the manuals can be found as PDFs
Vendors that cater to Ollds are Fusick, Year One, Parts Place, OPG, and Classic Industries. Start with the first 2.
How about some history on the car? All original? Restored? Been sitting for years? Origilal drive train et al.....
The wrong thing to do is to just start replacing parts without zeroing in on the root cause.
Always have the OEM parts rebuilt. Don't replace them with chinese parts and don't turn in your old cores for core credit.
Thanks for the info. Sorry, I don’t really know what else to say. The car starts jerking and I can only go about 30-35 mph. No, I don’t know anything about classic cars. This is my first classic car. I wanted to get a classic so I can work on it with my dad and grandfather and so I can eventually learn how to myself. Many of my family members know about cars. As for the history of the car, this is what the previous owner told me: rebuilt 330 V8, new air, fuel and oil filters, new fuel pump and tank, new q jet carb, trans service, diff service, booster brakes, all maintenances are complete.
Jerks as like it feels the engine is turning off and on repeatedly and the jerking is severe? Or is like a gentle surging where it feels like the rpm drifts up and down a little?
Last edited by oldcutlass; October 15th, 2023 at 10:05 AM.
Jerks as like it feels the engine is turning off and on repeatedly and the jerking is severe?
This kind of miss is usually ignition related. Rev the engine up and down while looking for spark jumping somewhere. You can also try it with the engine under a load by having friend sit in the car with the brakes on, revving the engine slightly while looking for spark jumping; if you do this, stand back!
Originally Posted by oldcutlass
Or is like a gentle surging where it feels like the rpm drifts op and down a little?
This kind of miss is usually, but not always, a fuel/carburetor issue.
If you think it might be an ignition misfire. Spray the spark plug boots one at a time with a squirt bottle of water and look for arcing. Its a shade tree power balance test.
The PO's info didn't mention anything about a recent tuneup, so sounds like a proper engine tuneup is in order. Spark plugs and wires, points, condenser, distributor cap and rotor, and check and set ignition timing. A failing condenser or cracked distributor cap can cause what you're describing.
Try to find new older stock tuneup parts. They're out there and will always give better results and performance than the modern offshore-made stuff in most parts stores, NAPA being a rare exception. Even their stuff ain't what it was.
You'll need a couple of specialized tools, namely a dwell meter/tachometer and a timing light. You can sometimes find good used ones on ebay, estate sales etc. Modern vehicles can't use them, so there's always some for sale. They're simple to use and anytime you're learning something is good.
Don't underestimate yourself- no one is born knowing how to do anything. And above all don't fall into the current "car guy" 🙄 trap that all old cars have to have an LS engine transplant to be usable now. That school of thought is complete bullshit and tells me the individual is too lazy or incompetent to know how to keep old machinery running.
You have a formidable Oldsmobile engine builder in Florida who often posts here, and the Oldsmobile Club of Florida is also there, based in Tampa area. OCF contact info: www.oldsclubofflorida.com, jspinella@msn.com. Someone in that group should be able to help you. If you were 12 hours closer I'd offer help and tools myself.
Hearing rumours another Olds group is trying to form in South Florida too if you're down that way.
Last edited by rocketraider; October 15th, 2023 at 11:48 AM.
Jerks as like it feels the engine is turning off and on repeatedly and the jerking is severe? Or is like a gentle surging where it feels like the rpm drifts up and down a little?
Do you notice that if you drive it easy it runs ok. But if you drive it harder you start getting the jerking concern?
Yes. It usually happens when I’m at a red light or just whenever I make a complete stop. I have to gently step on the gas, like to the point I feel I’m going only 10 mph, then I can slowly pick up speed. I feel like it takes forever to pick up speed though, and meanwhile there’s a line of cars behind me… I don’t stomp on the pedal cause I know that can cause the car to start jerking.
Can you post a picture of the carburetor with the aircleaner off? You mentioned a QuadraJet which is not stock for a 65. If it was originally a 4-barrel engine it should be a 4GC which is very different. If it was originally a 2-barrel engine and converted to 4-barrel we need to look into linkage adjustments.
If the 4GC is still in place, you need to know that this carburetor can be really sensitive to having the wrong gaskets in certain places, and can cause the off-idle stumble you're experiencing. A worn or badly adjusted accelerator pump can also cause it.
And hopefully NOT the case, the 1965 Jetaway transmission has a variable vane torque converter which is controlled by throttle position. If it's off adjustment it will make problems too, and if there is in fact a QuadraJet on there now, this could be the case.
You really need to get the 1965 Oldsmobile Chassis and Body Service Manuals. Original paper copies, not reprints and especially not CD-ROM or pdf copies. These are the same books the dealer mechanics used when the car was new.
Good luck. We'll help you get it straightened out.
Last edited by rocketraider; October 15th, 2023 at 06:49 PM.
Ok.
you most likely have a fuel flow issue. I know you are not a mechanic but there are some easy tests you can do to diagnose it. The first one is to disconnect the fuel line from the carb. Disable the distributor, connect a rubber fuel line to the line from the carb. Put the rubber line into a good sized container and crank the engine over for 15 seconds. You should have over 8 oz. Of fuel in the container after 15 seconds.
The second test is to get a vacuum gauge/ low pressure gauge and measure the fuel pressure. It should be around 5psi.
do these two test before you spend any money on parts.
Can you post a picture of the carburetor with the aircleaner off? You mentioned a QuadraJet which is not stock for a 65. If it was originally a 4-barrel engine it should be a 4GC which is very different. If it was originally a 2-barrel engine and converted to 4-barrel we need to look into linkage adjustments.
If the 4GC is still in place, you need to know that this carburetor can be really sensitive to having the wrong gaskets in certain places, and can cause the off-idle stumble you're experiencing. A worn or badly adjusted accelerator pump can also cause it.
And hopefully NOT the case, the 1965 Jetaway transmission has a variable vane torque converter which is controlled by throttle position. If it's off adjustment it will make problems too, and if there is in fact a QuadraJet on there now, this could be the case.
You really need to get the 1965 Oldsmobile Chassis and Body Service Manuals. Original paper copies, not reprints and especially not CD-ROM or pdf copies. These are the same books the dealer mechanics used when the car was new.
Good luck. We'll help you get it straightened out.
Definitely a Chevy-style QuadraJet. Looks like it's had an 80s factory aluminum EGR-equipped intake manifold installed too, my guess for clearance for the HEI distributor as well as the carb change.
You have a few modifications but we'll figure it out somehow. Neither the carb and intake nor distributor is a bad thing, just changes the way we have to diagnose things.
Can anyone see a vacuum advance can on that distributor?
Chris, take us a couple more pics. One of the "shelf" between the water pump and intake manifold, and the other of the front corner of the left hand cylinder head between the spark plug and the edge of the head. We can determine exactly what the engine is with the numbers and letters in those locations. The valve covers, oil fill cap and PCV look like 330 but I'm curious what's been done. I'm seeing some screwy **** with that carb and vacuum ports.
Last edited by rocketraider; October 16th, 2023 at 07:20 PM.
I normally say stick with a well-sorted QuadraJet but an Edelbrock carb and intake combination might work well for you, because I'm wondering how well the 307 intake ports match up to the 330 heads.
You'll have to tweak the throttle (and converter control switch if it still has it) linkage to get things functioning right.
Some Edelbrock intakes are set up to work with spreadbore carbs like a QuadraJet.
Keep asking, young friend. We'll get your 65 sorted to where when you mat the pedal it won't stutter and spit, but will let out a howl like the hounds of hell and be gone!
I normally say stick with a well-sorted QuadraJet but an Edelbrock carb and intake combination might work well for you, because I'm wondering how well the 307 intake ports match up to the 330 heads.
You'll have to tweak the throttle (and converter control switch if it still has it) linkage to get things functioning right.
Some Edelbrock intakes are set up to work with spreadbore carbs like a QuadraJet.
Keep asking, young friend. We'll get your 65 sorted to where when you mat the pedal it won't stutter and spit, but will let out a howl like the hounds of hell and be gone!
So those numbers mean it’s a 307 intake instead of a 330?
October 13th, 2023, 05:18 PM
