Car jerks/hesitates/surges

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Model T Ford Forum: Forum 2016: Car jerks/hesitates/surges
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Thursday, June 16, 2016 - 12:30 am:

Car surges at low rpm, not the engine but the car itself. If I apply slight pressure to the brake it stops surging. If I accelerate, it stops. It did this with the old engine and is continuing to do it with this new engine. Iím suspecting something worn between the universal joint and the rear end.
Any ideas?

Rod


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Thursday, June 16, 2016 - 02:15 am:

I would expect vibration from a worn U-joint. Has the rear axle been rebuilt?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Burger in Spokane on Thursday, June 16, 2016 - 02:23 am:

Car jerks ? You mean those know-it-all blowhards at car shows ??? :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, June 16, 2016 - 07:36 am:

Maybe a bad pinion bearing or u- joint or driveshaft bushing or all of the above.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Thursday, June 16, 2016 - 10:52 am:

Thanks for the responses, I have found a thread
http://www.mtfca.com/discus/messages/506218/543262.html?1432328086
that kind of covers what's going on, so I will try and solve the issue.
Steve, Royce, your thoughts are what came to mind initially, so I'll ck it out.

Rod

pie


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dick Lodge - St Louis MO on Thursday, June 16, 2016 - 11:00 am:

Burger's mind works like mine does. I reacted to the thread title the same way.... :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Thursday, June 16, 2016 - 11:02 am:

If the Polly sign is 25Ĺ", it's one of mine. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, June 16, 2016 - 11:29 am:

How does the engine idle? Sometimes the fuel mixture tends to "load up" at low speeds. Caused by a rich mixture. This would change when you open the throttle or apply the brake.

Other things could be ignition problems. Try retarding the spark when you are running very slowly. This might smooth things out.

This is what I think is happening. You have some fuel mixture problems or spark too advanced which cause the engine to run rough at very slow speed. This in turn is amplified by some slack somewhere in the drive train. Could be in the U joint or the rear axle.

This problem is quite similar to a front wheel shimmy which appears when you hit a small bump and then the wobble begins because of loose parts in the steering system.

Hope this helps.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Thursday, June 16, 2016 - 12:15 pm:

Burger, Dick, sorry for the misleading title,

Steve, yup it is 25-1/2". Are you the maker. I bought them from "Vics" in Seattle. Very nice work.

Norman, I will try your suggestions changing timing and fuel mix. The engine is running a Texas T distributor and it had a
Texas T modern carb on it, but I replaced it with a rebuilt Holly NH. I'd be surprised if either the timing or fuel mix was the problem as it did the same thing with the original engine that was running a timer, buss coils ans a different Texas T Carb. But then strange things do happen.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Lloid on Thursday, June 16, 2016 - 01:18 pm:

Its sounds like fire or lack of or carb issues. Just what i would check but i haven't had Ts all my life. Tim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Thursday, June 16, 2016 - 03:28 pm:

I jacked up the rear of the car and I can move each tire about 4 inches back and forth. Then I checked the movement on two other T's and they moved also, but only about 2".
How do I determine what is causing the difference, or is this not the cause of my herky jerky movement?

Rod


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Thursday, June 16, 2016 - 03:33 pm:

Has the rear axle been rebuilt with bronze thrust bushings? Try pulling each rear wheel in and out with the rear end jacked up off the floor.

http://www.dauntlessgeezer.com/DG79.html


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Thursday, June 16, 2016 - 04:59 pm:

I like Burgers comment.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, June 16, 2016 - 06:05 pm:

Rod,
Do you mean movement 4 inches radially, or 4 inches in and out? In and out would be very dangerous. There should be no noticeable in and out movement.

The radial movement can come from any or all of many sources, such as gear lash, universal joint wear, or differential wear. There is usually some radial movement, but 4 inches at the rim, seems like too much.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Thursday, June 16, 2016 - 06:55 pm:

Mark,
There is virtually no in/out movement with the wheels jacked up.

Norman, it is radial movement, sorry for not being clearer.

I have been fooling with the mixture and timing and am making some progress. It's either getting better or I'm getting used to it ;)

This forum is awesome, thanks for all the helpful tips.
Rod


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Dunlap on Thursday, June 16, 2016 - 10:08 pm:

Rod:
I am far from an expert on such matters, but you might consider double checking your coils. My 24 coupe gets a little herky jerky when one of the coils vibrates slightly up and out of position. Once I slide it back down into a firm position in the box, it runs smoothly. Hope your problem is something that simple.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Thursday, June 16, 2016 - 10:33 pm:

Really couldn't see this as a drive train problem. Especially without accompanying noise but decided to wait & see till the guys came around. Fuel & ignition. Your float level could be so low you,re starving. Coils: what shape are they in? (Replaced caps, HCCT'd?). Lastly your driving habits.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Thursday, June 16, 2016 - 11:58 pm:

When I started making signs about 25 years ago I got the steel blanks from a local barrel factory. Those were 25.5", so that has been the size of the round signs ever since. I sold the business, but the signs are still being made.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Friday, June 17, 2016 - 12:32 am:

No coils, well it has one as well as a Texas T distributor. Also a rebuilt Holly NH that was rebuilt by Mark Chaffin, so I doubt there's a float issue.
I'm thinking I'm on the right track by following the previous advice tuning the carb mixture and timing. It seems to be improving.

As a side note, I had the same issue with my crate engine 66 Mustang. In that case a brand new intake manifold was improperly machined and caused a lean miss that took forever to find. Internal leak.

Rod

Rod


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, June 17, 2016 - 08:37 am:

It might just be driving technique. You may need to wind up higher in low gear before dropping into high.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rod Letcher - Eugene Oregon on Friday, June 17, 2016 - 09:50 am:

Royce, good point, but I have two other "T"s that don't suffer this problem. Of course I could be an inconsistent driver ;)

Rod


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