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acceleration hesitation jerking and stalling

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Nov 14, 2015, 5:03 AM

Post #1 of 5 (703 views)
acceleration hesitation jerking and stalling Sign In

i have a manual 3 speed 1965 mercury monterey 390 2v 300+miles. ok so since i bought the car in january of this you ive been putting regular unleaded gas with a lead additive. a few days ago i was told to put non oxygenated, or non alcohal gas??? in it, and shortly after that is when it started hesitating and jerkin while driving. even at higher speed i can feel it. ive done my own troubleshooting online. from plugs n wires being the problem, ignition system stuff, fuel filter injector, air filter, but i have a strong feeling that changing the gas is why it started doing it. i am no professional certified mechanic by any means obviously, nor do i have a lot of money to pay for all these things that might be the problem. i bought this car for the general style of it, and to learn how to work on and fix my own vehiles. i trust the shop guys, but i know some like to jerk you around if they know you dont know a lot about cars. if anybody could help me out here and give me some good insight itd be greatly appreciated. thanks

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 14, 2015, 6:31 AM

Post #2 of 5 (696 views)
Re: acceleration hesitation jerking and stalling Sign In

Everyone says that old school vehicles are simple, non complicated and easy to work on. Some of that is true when it comes to actual repairs but when it comes to diagnostics, you have no computer or stored codes to point you in the right direction. For this you have to rely on good ole diagnostic experience. Someone knowledgeable needs to look at this issue and first determine if you are dealing with an ignition type of problem like a misfire or a fuel distribution issue. That can only be done by observing and recognizing the symptoms


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 14, 2015, 6:51 AM

Post #3 of 5 (692 views)
Re: acceleration hesitation jerking and stalling Sign In

Maybe you do have bad fuel or it contains water. You could always drain the tank and refill it with what you were using in the beginning to see if it runs better. Take the fuel filter off and see if there is water in it.

Probably wouldn't hurt later on to pull the heads and have the seats changed, so you don't need to add the lead.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Nov 14, 2015, 6:52 AM)

Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 14, 2015, 7:26 AM

Post #4 of 5 (685 views)
Re: acceleration hesitation jerking and stalling Sign In

Notes: Has a crumby trans from new in '65 IMO when they weren't old but not really the issue.
Fuel sure is. Forget the additives. Not sure if the "ethanol" stuff sold really works and cancelling its ill effects on gaskets and rubber products that can't take it.
Remember if car was a 2V on a 390 it stated "Regular" gas which was 93 octane! Premium started at 98!

They do OK on 93 current premium just detune timing some.

Carb issues include: Very early issues with chokes on all of these when not even cold. Should have an OE design to pick up actual exhaust thru tube into choke spring that was a constant issue. Any vacuum diaphragms, accelerator pump, and carb in general really should be redone with real new parts not an old kit and probably been done a few times at the age already.
It must have had a long life of leaded fuel which was also a problem as well as carbon build up and making a mess sometimes on valves. Sometimes just copious carb cleaning would really do or a safe beating meaning from a stop floor it to limits of trans to change up to next gear and watch the cloud of junk out the tailpipe worked done a few times.
What is the current ignition system OE or altered in any way? Even if not that oil and points look for transfer of metal from one to the other if any change condenser. If none leave old one in forever as it matches.
Do you have a dwell/tach? It's by far the best way to get distributor right and can tell you how worn distributor shaft bushings are as well another problem with age lots younger than this,



Nov 18, 2015, 5:21 AM

Post #5 of 5 (657 views)
Re: acceleration hesitation jerking and stalling Sign In

One problem I had with an older car with simular symptoms is rotted fuel line where it goes up and over the rear axle. It won't leak fuel because it's at the top but the fuel pump will just suck more and more air. FYI

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