Runs rough at higher speed

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Model T Ford Forum: Forum 2013: Runs rough at higher speed
Top of pagePrevious messageNext messageBottom of page Link to this message  By Gordon Drisko on Sunday, May 05, 2013 - 06:44 pm:

Why does my 23 Coupe run well at lower speeds (maybe 25mph),but acts like it's going back to 3 cylinders when I try to speed? I have a new timer and rebuilt carburetor. Any ideas?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hap Tucker in Sumter SC on Sunday, May 05, 2013 - 07:01 pm:

From the 1921 instruction manual located at: http://www.mtfca.com/books/bookmenu.htm

ENGINE LACKS POWER-RUNS IRREGULARLY
At Low Speeds.
1. Poor compression-account leaky valves.
2. Gas mixture too rich or too lean.
3. Spark plugs dirty.
4. Coil vibrator improperly adjusted.
5. Air leak in intake manifold.
6. Weak exhaust valve spring.
7. Too great clearance between valve stem and push rod.
8. Too close gap between spark plug points.
At High Speeds.
1. Commutator contact imperfect.
2. Weak valve spring.
3. Too much gap in spark plug.
4. Imperfect gas mixture.
5. Vibrator points dirty or burned.

I would also share that I have seen trash/rust in the fuel line or carburetor inlet that would can allow enough gasoline so the car would idle ok but not enough to run well at higher engine RPMs. Also sometimes coils that are not properly adjusted and or that need rebuilding could be adding to the problem. Are you running on battery or magneto? Is the front plate for the timer centered on the camshaft or is it off some? Does it run badly immediately when you go say 30 mph or does it take it a little while before the problem starts? If it takes a little while be sure the vent in the gas cap is not clogged up. Those are a few initial items I would suggest looking at.

Good luck and let us know what you find.

Respectfully submitted,

Hap l9l5 cut off


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Sunday, May 05, 2013 - 07:52 pm:

What carb type do you have and do you have the original hot air pipe properly attached?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Sunday, May 05, 2013 - 08:03 pm:

Sometimes, when I forget to turn the key to "mag", the car begins to run rough at about 30 mph.

That is a reminder to me to change from "batt" to "mag". When switched, the engine immediately smooths out because the coils prefer the power produced by the magneto rather than the 6 v batt.

Could it be that your car does not have magneto power, or the magneto is not functioning properly?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Sunday, May 05, 2013 - 08:03 pm:

Are you running coils and have they ever been rebuilt? What Timer are you using?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Marshall V. Daut on Sunday, May 05, 2013 - 08:35 pm:

If you have an in-line filter between the gas tank and carburetor, remove it and go for a high speed spin. Some filters can't flow enough fuel in a gravity feed system to keep up with higher speeds. Definitely run on the magneto to achieve smoother high speed operation.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Sunday, May 05, 2013 - 08:37 pm:

Strainer/filter, high speed circuit in the carb, coils, timer. In that order.

If we assume your timer and carb are OK, make sure strainer isn't clogged. If not, probably coils.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Sunday, May 05, 2013 - 08:50 pm:

Mine did that when the timer was off-center. Or add gasoline?.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Hylen- Central Minnesota on Monday, May 06, 2013 - 08:25 am:

Before you spend a bunch of money, try pulling the left lever down further. A high speed stumble can be as simple as too little spark advance. This is especially true when running on battery rather than magneto.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, May 06, 2013 - 09:54 am:

If that list is "as published" it's all over the place. I mean there's no progression from easy/likely to hard. I'd start with mixture or timer or plugs not compression. Same with #2. Valve spring would be last.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gordon Drisko on Saturday, May 25, 2013 - 09:25 am:

Thanks for all of the help from you guys. I had a new ANCO timer from Langs, a new gas tank and a completely rebuilt carb I was running the plastic coils that came in the car. I changed to some used wooden ones and saw an improvement. However when running on mag I got some skipping. Isolated that to one coil,changed it out and got more improvement. Then bought the timer rod bending tools and setup gauge and really adjusted the timing. Runs steady and strong now!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Saturday, May 25, 2013 - 10:08 am:

Gordon,

The coils need to be properly adjusted for best performance. There is someone in your area with a hand cranked coil tester that can be used to properly adjust them for you. Or you can send them to one of the coil specialists listed on the Vendor section of this web site.

The plastic coils can be adjusted properly too. Often they were made with improper capacitors. You can check those and replace them yourself easily. The capacitors are quite inexpensive. Good ones can be found at http://www.funprojects.com


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Saturday, May 25, 2013 - 10:33 am:

Gordon

Advice is worth what you pay for it, here's mine:

Start with fuel flow, fuel valve, strainer, filter (I hope you don't have a separate filter), and finally carb air passages and float setting.

Next is electrical: timer clean and centered, coils adjusted properly, timing properly advanced. Try another set of plugs. Modern ones are a cheap way to test.

I would NOT start with valves/compression. Seldom does a car idle and run ok at low speeds and run badly at high speeds with engine problems. Not impossible but rare in my experience. As a last resort check compression.

Hang in there, I'll bet its a small thing!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Wells on Monday, May 27, 2013 - 05:36 pm:

I had that problem too so, I installed new points on my coils and set them up so the cushion spring follows properly. This is without using a coil tester BTW. I also installed new capacitors in the coils. Runs perfect now. A friend of mine also had the high speed miss. We tried my coils in his car. It ran perfectly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Monday, May 27, 2013 - 07:13 pm:

Probably is the coils but I have had the same problem and the cause was a worn timer with the roller jumping at high speeds. Check the timer and be sure it is centered properly. In my case the shaft the roller rides on had worn through the side supports so the roller could flop around.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Monday, May 27, 2013 - 08:02 pm:

There's an article in the repro book, "Secrets of Speed" titled, "Ford "Steady by Jerks" Ignition."


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Wells on Monday, May 27, 2013 - 10:22 pm:

Actually Val, now that you mention it, I also had the same timer problems you did when I first got my car so yes, it could be that too.


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