Rough acceleration and coughing back through the carb

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Reno Speedster
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Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sun Jun 26, 2022 8:49 pm

I have done some work on my 22 and have been driving it a bit. At first, it ran very smoothly but after driving it around for an hour the other day, it started to sputter and pop when I try to accelerate. It has a pretty smooth idle.

I have checked the electrical and it’s getting spark on all cylinders. Shorting each plug showed a noticeable change. I the fuel is new, no sediment in the bowl, and the carb is clean as a whistle inside. The carb appears to be a newly rebuilt NH. I adjusted the mixture and did get a bit smoother at idle, but no real improvement when accelerating. I pulled the plugs and they were a bit sooty, but the spark areas were clean. With the hood off, I can see some puffing back out through the carb when I am trying to start it.

This is a rebuilt motor with not that much time on it and it had been sitting for 7 years.

I am thinking that I might have a sticking valve, which I am going to check. Any other ideas?


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Re: Rough acceleration and coughing back through the carb

Post by KBurket » Sun Jun 26, 2022 8:57 pm

I had similar symptoms. Changed carbs, put in new plugs, new plug wires, charged my battery but it continued sputtering at higher acceleration. Read on the forum about keeping the spark plug wires separated so I cut the zip ties I used to gather the wires together and separating them resolved my sputtering


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sun Jun 26, 2022 9:17 pm

Thanks for the tip. They appear to be separated, but I will double check. One of the plug wires (the front one) shows signs of being heated (black stuff bleeding through). It runs over the exhaust manifold. But, as I said the spark still comes through. I will add a new set of wires on my next part order.

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Re: Rough acceleration and coughing back through the carb

Post by Craig Leach » Sun Jun 26, 2022 9:33 pm

Never to old for new tricks my son-in-law showed me if you take a spray bottle and mist water on the plug wires with the lights out and they ark it will ark under lots of driving conditions.
Craig.


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Re: Rough acceleration and coughing back through the carb

Post by TXGOAT2 » Sun Jun 26, 2022 9:58 pm

You may have a tight valve adjustment or a rusty valve. I'd check everthing else before messing with the valves. Any plug wire that looks bad probably is bad. Many plug wires that look good aren't. A plug wire can emit a spark when held close to the cylinder head and yet still not fire the plug reliably when the engine is running.
Last edited by TXGOAT2 on Sun Jun 26, 2022 10:05 pm, edited 1 time in total.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sun Jun 26, 2022 10:05 pm

I plan to pull the valve covers and make sure that they are all
Moving. A little oil couldn’t hurt.

I forgot to mention that it does it on both battery and mag.


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Re: Rough acceleration and coughing back through the carb

Post by TXGOAT2 » Sun Jun 26, 2022 10:10 pm

If it puffs back through the carburetor when cranking the engine with the ignition OFF, it suggests a valve problem, perhaps sticking or carbon fouling. If it puffs back through the carburetor when cranking with the ignition ON, it suggests an ignition problem, such as bad coil box insulation or bad plug wire insulation, or perhaps a commutator wire shorting to ground and firing the cylinder out of time.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sun Jun 26, 2022 10:36 pm

Thanks for the tip. The commutator wires are new so it shouldn’t be that. They were replaced because one of the wires was frayed and possibly shorting. Frankly, I just replaced all of the wiring because it was a little tatty. But, the problem occurred before and after the wiring was replaced. The only wires not replaced were the plug wires. So, that’s probably a thing to try.


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Re: Rough acceleration and coughing back through the carb

Post by jiminbartow » Sun Jun 26, 2022 10:45 pm

What is the float set at? Jim Patrick

32CA8DC2-7DFA-4E43-B724-6D15C76C2555.jpeg
Last edited by jiminbartow on Fri Jul 01, 2022 10:38 am, edited 1 time in total.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Mon Jun 27, 2022 12:33 am

Good question. I will check it and make sure it’s in spec. When I first put gas in the car, it poured out of the carb. A couple of taps with a hammer handle sorted that. I did get some dripping out of it later, but only a little. I took the carb off to see if there was crud in it that could be blocking things, but it was all clean and looked new.


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Re: Rough acceleration and coughing back through the carb

Post by Norman Kling » Mon Jun 27, 2022 1:03 am

Some of the "rebuilt" carburetors have a gros jet instead of an inlet needle valve on the float. These are notorious for not letting in enough fuel and could clog up with just a very little sediment in the fuel.
You might check and if it has one replace with a needle valve and set the proper float level.
Norm


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Mon Jun 27, 2022 1:24 am

I was not sure what a gross jet looked like or where it went, but a search of the archives found a good post with pictures. Mine dose not have a gross jet. It’s a point style that has what appears to be a nitrile or similar tip. All very clean.


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Re: Rough acceleration and coughing back through the carb

Post by TXGOAT2 » Mon Jun 27, 2022 7:36 am

**"With the hood off, I can see some puffing back out through the carb when I am trying to start it."**
If it does this with the ignition OFF, you most likely have an intake valve problem.


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Re: Rough acceleration and coughing back through the carb

Post by Norman Kling » Mon Jun 27, 2022 10:44 am

Assuming, you just started a "rebuilt" engine, did you torque the head bolts? If a steel head this should be done while hot after running the engine. The manifolds should also be tightened while hot. If you have an aluminum head, torque after you warm it up and then cools down again. A leak at either the manifold gaskets or the head gasket could cause the engine to run lean or even allow water to get into the cylinders.
A sticking valve is unlikely to appear after driving. It usually happens when the engine has been setting a long time and some rust might be formed holding one or more valves open.
Another thing which could happen is that if you have adjustable valve lifters, one of them might have changed to a lower clearance, so check the valve clearances.
Norm


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Mon Jun 27, 2022 3:52 pm

Thanks, I will check the torque on the head. I don’t see any evidence of a water leak (external, into the oil, or into the cylinders) but it’s good to check.


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Re: Rough acceleration and coughing back through the carb

Post by Altair » Mon Jun 27, 2022 4:13 pm

All the suggestions are good usually spitting back through the carb indicates a lean condition, a lean condition can be traced to a loose carb, loose intake manifold and non tight fitting spark plugs, they are pipe threads and don't seal that well. Additionally a contaminated carb can cause some issues, but with spitting back through the carb and rough running indicates a lean condition. A quick check of the spark plugs is to pour about a teaspoon full of water around the plug and look for excessive bubbles, there may be some bubbles but excessive is problematic.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Mon Jun 27, 2022 10:22 pm

Thanks for the tip. The carb and manifold are tight with good gaskets. But, I will check that as well.


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Re: Rough acceleration and coughing back through the carb

Post by Jerry VanOoteghem » Tue Jun 28, 2022 6:44 pm

Did you double check your timing? What condition is your timer in? Have a look inside of it.


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Re: Rough acceleration and coughing back through the carb

Post by noelchico » Tue Jun 28, 2022 9:41 pm

Make sure that when you replaced the timer wires that they didn't get crossed. I've seen experienced T mechanics make that mistake. The firing order is 1-2-4-3. Slowly turn the engine over with the battery on and check what plugs fire.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Tue Jun 28, 2022 10:59 pm

I will check the timer, but it’s basically as new. When I changed the wires, I took one off at a time so there should not be a mix up. But, it’s always good to be sure.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Thu Jun 30, 2022 10:46 pm

I got some time to tinker today. I took the valve covers off and the valves and lifters looked good and oily. They all moved up and down smoothly with the hand crank. While fiddling with other things later, the car actually started on compression, which is a good sign. I didn’t have the correct gage (or a worn dime) to check the valve clearance. I will do that later.

I replaced the plug wires and made sure that the new wires did not touch. It appears to have solved the spitting back through the carb issue, but didn’t fix the rough acceleration.

I cleaned the timer, which is a new roller timer and made sure that the wires were not shorting.

I took the carb off and checked the float for leaks (none) and adjusted the float, which was app 1/8 inch low. I am going to throw the carb in the sonic cleaner with some hot soap and water in case there is some crud in the high speed passage. Everything else looks good. I am going to put new gaskets on the carb when it comes out. I also found there were two gaskets between the carb and manifold. Not sure if that was an issue, but a new one can’t hurt.

It feels like a fuel starvation issue since it will idle on but stumbles on acceleration. I just can’t figure out where the problem lies. The sediment bowl is clear, the tank looks clean, no inline fuel filter, and there was nothing in the carb bowl. The issue starts from cold so I don’t think its caused by vapor lock (the fuel line does pass over the exhaust).
Last edited by Reno Speedster on Fri Jul 01, 2022 12:45 am, edited 1 time in total.


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Re: Rough acceleration and coughing back through the carb

Post by TXGOAT2 » Thu Jun 30, 2022 11:33 pm

Low float level and/or adjustment not open far enough could cause your issues. I agree that it's not vapor lock. If the problem gets better with the engine fully warmed up, it suggests a lean condition, which is usually most evident when the engine is cold. Correcting your float level may do away with the problem. Late timing can also cause jerking and spitting back at the carb, especially before the engine warms up.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Fri Jul 01, 2022 3:10 am

Ok, although the carb looked clean, the second time it came out of the car I decided to take the needle and seat out to see how things were and discovered a bunch of brown stuff inside the carb. It looks like dried fuel varnish and some light rust. I am soaking the carb body in Hoppies No. 9, which does a good job on rust and dried varnish. I have cleaned the parts that can be removed and scrubbed what I can reach in the carb with bronze brushes. I will try to blow out the idle and high speed passages with compressed air, but I might need to drill out the brass plugs to get them clean. Hopefully, this is the problem.


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Re: Rough acceleration and coughing back through the carb

Post by Jerry VanOoteghem » Fri Jul 01, 2022 8:45 am

I think you're on the right track.

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Re: Rough acceleration and coughing back through the carb

Post by Craig Leach » Fri Jul 01, 2022 10:01 pm

Hi Morgan,
Hoppies#9 for cleaning model T carbs, I'm proud of you @ $130 a gallon that never crossed My mind. It is really good stuff just never thought of it for that purpose. I'm still trying to get over Stoddard solvent @ $17.50 a gallon if you can get it. I'm cruising Walmart for carb & brake clean. I know some people going to gasoline to clean parts and it's close to $6.00 a gallon here. And its damn dangerous to use.
Craig.


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Re: Rough acceleration and coughing back through the carb

Post by DickC » Sat Jul 02, 2022 1:09 am

I'm still learning about Model T's after having owned, driven and worked on them for over 50 years. So bare with me. I don't know the year of your T but if it is one that you drive with a mag vs battery you may want to check the mag output. I have had the same kind of issues with an early T running on mag.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sat Jul 02, 2022 8:01 pm

I am a gunsmith and have used Hoppies to clean up lots of old guns and machine parts. You don’t need a gallon to do it, you just need to keep the part wet. My method is to put the part in a thick gallon plastic bag, spray it with some Hoppies, and seal the bag with as little air as I can get inside. Then you just move the bag to slosh the little bit of Hoppies around to keep the part wet. The bag keeps it from evaporating or running away. Works like a champ and does not take much.

In any case, after cleaning with Hoppies and carb cleaner and half an hour in the sonic cleaner, I reassembled the carb with new gaskets and reinstalled it. Sadly, it did not fix the issue.

I am going to drain the tank and make sure that it and the fuel line are clean. If that does not fix it, I will try drilling out the brass plugs in the carb to make sure the low speed circuit is not plugged. Everything else is clean in the carb.
Last edited by Reno Speedster on Sat Jul 02, 2022 8:06 pm, edited 1 time in total.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sat Jul 02, 2022 8:05 pm

DickC wrote:
Sat Jul 02, 2022 1:09 am
I'm still learning about Model T's after having owned, driven and worked on them for over 50 years. So bare with me. I don't know the year of your T but if it is one that you drive with a mag vs battery you may want to check the mag output. I have had the same kind of issues with an early T running on mag.
This one is a 1922 Runabout pickup. It has a starter and the issue happens on both battery and mag. The issue feels like fuel and the compression is good (it starts on compression). The spark appears to be ok, but if I can’t find anything in the fuel system, I will have to go through the electrical system again.
Last edited by Reno Speedster on Sat Jul 02, 2022 9:59 pm, edited 1 time in total.


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Re: Rough acceleration and coughing back through the carb

Post by Reno Speedster » Sat Jul 02, 2022 9:36 pm

And then….. a miracle occurred. After taking my son to the movies, I came out and started the car to confirm that it still was happening on both battery and mag and when I switched to mag, it ran like a dream. I drove it around for about an hour and it did great. When I switch to battery it runs rougher but not terribly. Not sure what that’s about, but it is nice to have it running well. I will drive it again tomorrow and if things go well, I have an invite to drive in the 4th of July parade with the Antique Auto Mushers.


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Re: Rough acceleration and coughing back through the carb

Post by TXGOAT2 » Sat Jul 02, 2022 10:38 pm

I've seen rust block small passages in cast iron carburetors. Most solvents will not affect it.

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