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Intermittent Rough Idle/ Loss of Power |
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cyates176FA 
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Joined: 12 Apr. 2022 Location: EAST TENNESSEE Status: Offline Points: 132 |
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 Topic: Intermittent Rough Idle/ Loss of PowerPosted: 24 July 2022 at 9:51pm |
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Apologies in advance for this long-winded post. Backed the Jeep out the other night to clean it up for the
weekend. Noticed some black smoke from the tailpipe. It was sooty black smoke
that smelled like carbon and a little bit of raw fuel (not sure what else it
would smell like, haha). Figured it was running rich, so I adjusted the idle
screw, and it improved a bit; but was still putting out puffs of black smoke. Took
it out for a test drive, and it occasionally would go into a very rough idle,
with very little power. Once I got it started back up, it ran well and had good
power and acceleration - but still a little bit of black smoke. A little background information 1. 1. Recently had a stumbling issue that was corrected with a tune up (new plugs, distributor cap, and coil). Ran fine after that – for a few weeks at least. Haven’t messed with the timing or anything between then and now. 2. 2. New
mechanical fuel pump, new fuel filter, and a pressure regulator set to ~3 psi. 3. 3. I
have a Solex carb on the Jeep. I pulled and cleaned the jets when I was having
the stumbling problem about a month ago. Ran fine after reinstalling the carb –
until just the other day. A few things that stand out now that I’ve thought about it 1. 1. When
I was troubleshooting the previous stumbling issue, I pulled the carb off, and
noticed that there was a lot of carbon in the intake manifold. Could that be
due to misadjusted valves? 2. 2. The
current stumbling issue is temporarily “cured” once it backfires through the
tailpipe. Can’t think of anything that would cause that to “cure” it. 3. 3. I
can tighten the idle screw basically all the way (until the spring is fully
compressed) and it doesn’t change the idle very much at all. This makes me
think there is air getting in – possibly a leak in the manifold gasket? 4. 4. When
I pulled the plugs, they had a lot of carbon buildup. It was chalky and dry, so
I’m pretty sure it isn’t oil. Is the carbon in the intake the cause or effect of the
carbon showing up on the plugs – and is it linked to the intermittent rough
idle/ poor power? When the engine idles good, it sounds great – responsive throttle
and even RPMs. When this stumbling and loss of power happens, I can barely get
it to move – and the idle is very sporadic with a lot of popping from the
tailpipe. I’ve had the Jeep since last fall, and I’ve not adjusted the
valves – is that where I should start? Could the carbon be occasionally not
allowing a valve to fully close? |
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Steelyard Blues
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Joined: 09 Oct. 2017 Location: Reno, NV Status: Offline Points: 1500 |
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Posted: 25 July 2022 at 10:49am |
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Chalky and dry is usually running rich and not burning oil. You should not see carbon in the intake.
Backfiring through the exhaust might be unburnt fuel getting ignited and possibly incorrect timing. I would reexamine your carb to make sure the choke is not sticking, the float is working properly and that the diaphragm for the "power valve" is not split. Check the timing, dwell and distributor connections. Several people on the forum report issues with new condensers. Micah
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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cyates176FA
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Joined: 12 Apr. 2022 Location: EAST TENNESSEE Status: Offline Points: 132 |
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Posted: 25 July 2022 at 11:02am |
Is it worth pulling and cleaning the manifolds, checking the valves, and going back with new gaskets? The PO didn't do much engine work at all, so I'm not sure how old those gaskets are. I've also seen posts about the PCV being clogged causing some symptoms like what I'm seeing now. Any experience with that?
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Oldpappy
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Joined: 09 Apr. 2018 Location: Tennessee Status: Offline Points: 4908 |
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Posted: 25 July 2022 at 11:22am |
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Cory,
Would help to know what engine you have. I assume it is a L134 ? Carbon in the intake could mean leakage around intake valves, but I would expect some backfire through the carb. I don't have much experience with the Solex but I don't think they have an actual "choke" but some sort of enrichment circuit instead. The "power valve" is also called an "accelerator pump", and if the diaphragm is leaking it would cause excess fuel delivery which could cause an over rich mixture bypassing the other circuits of the carburetor. As Micah said there have been a lot of problems with the condensers on the market today. Most suppliers sell imported tune up kits and the condensers are junk. Napa still has good quality tune up parts, but I have been using "Blue Streak" branded points and condensers from Classic Military Vehicles for a couple of years and they are reliable.
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If you can't get there in a Jeep you don't need to be there!
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Steelyard Blues
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Posted: 25 July 2022 at 11:33am |
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Oldpappy,
Thanks, I drew a blank on the name and was thinking of a Holey carb and the term "power valve." Cory, I would not mess with your intake and exhaust. Running rich points to something other than an air leak. Messing with the manifolds could lead you down the rabbit hole of broken studs. Some things are best not messed with unless you have to. I would not expect the PCV to be causing your issues. One other thing to check is your air filter. If clogged or too much oil, it could cause the engine to run rich. 23 & 24 are your accelerator pump assembly. Micah   Edited by Steelyard Blues - 25 July 2022 at 11:41am |
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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Bruce W
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Joined: 29 July 2005 Location: Northeast Colorado Status: Online Points: 9651 |
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Posted: 25 July 2022 at 12:09pm |
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Carbon in the intake manifold - heat control valve?
BW
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It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
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cyates176FA
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Posted: 25 July 2022 at 12:46pm |
I'll check that tonight to make sure the counterweight/ spring are moving correctly. Is it possible for the external components to move and not the internal portion?
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Steelyard Blues
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Posted: 25 July 2022 at 1:05pm |
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Bruce,
Unless I'm missing something, the intake and the exhaust are walled off. There would be no way for the two to mix. Cory, Is the intake deposits fluffy like you see on the spark plugs or is it just the excessive fuel that is darkening the inside of the intake manifold? Micah
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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cyates176FA
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Joined: 12 Apr. 2022 Location: EAST TENNESSEE Status: Offline Points: 132 |
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Posted: 25 July 2022 at 1:08pm |
The deposits in the intake are like dry chalky crumbs - somewhat similar to the carbon on the plugs. I can put my finger in the intake and the pieces that come out break down between my fingers into basically black soot.
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Bruce W
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Posted: 25 July 2022 at 1:38pm |
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When the heat control valve is closed (“cold” position) the exhaust flows around the central part of the intake manifold, inside the “box” that you see from the inside. The intake can easily become hot enough to cook any liquid fuel. This intake manifold is a very primitive and poor design and there is almost always liquid fuel in the bottom of it.
BW
Edited by Bruce W - 25 July 2022 at 1:42pm |
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It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
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cyates176FA
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Posted: 25 July 2022 at 1:56pm |
If the heat control valve were sticking, could that prolonged or intermittent exposure to the exhaust heat be causing some of these problems?
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Steelyard Blues
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Posted: 25 July 2022 at 6:55pm |
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Bruce,
I guess that may explain the deposits the OP is getting but it would have to get pretty hot. My Solex is difficult to hot start from the heat soak boiling out the fuel. Once running, there is no heat issue and certainly not something that would cause her to run rich. Usually when the heat riser is stuck closed, people seem to report that the engine temps are higher. I don't recall anyone mentioning a rich mixture. The deposits in the intake make no sense to me but not seeing it in person makes it difficult to assess. Unless one considers that the cam might be out of sequence. This would explain the backfiring and possibly flowing back into the intake. OP does not indicate any backfiring through the carb though. I'm still leaning towards the basics: ignition and carb. Since there is no effect when the idle mixture screw is all the way in. Fuel must be getting out somewhere. Some pictures may help us see how things are set up. Micah
Edited by Steelyard Blues - 25 July 2022 at 6:56pm |
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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cyates176FA
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Joined: 12 Apr. 2022 Location: EAST TENNESSEE Status: Offline Points: 132 |
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Posted: 25 July 2022 at 7:22pm |
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I don’t really get much backfiring through the carb - though it will occasionally sputter fuel out of the throat of the carb when the engine stalls during this rough idle. Generally if it backfires, it’s through the tailpipe.
Regarding operating temp, I don’t recall it being higher than normal - normally around the 190°-ish mark. I may take the Solex off to get some pictures of the deposits in the intake. I can also take the PCV line off to make sure it’s not blocked. I keep circling back to air getting in somewhere; but I feel like it would idle rough all the time, which it doesn’t. Sometimes it won’t idle and I have to hit the throttle to keep it going, other times it’ll rough idle on its own - and then other times it’ll just hum right along. I pulled and cleaned the plug yesterday before taking it out and when I checked then when I got home, they were nearly as carbon-fouled as before I left. And I drove maybe a total of 40 minutes. I admit that carburetors are a bit of a blind spot for me, so I’m a little slow on troubleshooting then. Could air leaking in pull more fuel through the carb, and make the idle screw less effective? I can stall the engine by completely blocking the carb with my hand.
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Steelyard Blues
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Posted: 25 July 2022 at 9:36pm |
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Air leaking around the carb means less air going through the carb which then causes the engine to run lean and not rich.
At idle, the throttle plate is barely open and the idle mixture literally just drips in a little bit of fuel. The venturi is generally not contributing much if anything. Did you check the choke?
If you are going to take the carb off, I would completely disassemble it and give it a thorough cleaning. There is not much to these carbs. If unsure, take lots of pictures as you disassemble. I like using brake clean to clean out the passages. Check the float and make sure it is not water logged. These carbs are metric. I have taken mine apart multiple times without replacing gaskets. These are really simple carbs. Do you have the correct base gasket? Micah |
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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cyates176FA
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Joined: 12 Apr. 2022 Location: EAST TENNESSEE Status: Offline Points: 132 |
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Posted: 25 July 2022 at 9:49pm |
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Haven’t checked the choke yet.
The base gasket is the thick gasket with the metal “V” that goes down into the intake - which I believe is the correct one. I will take the carb off tomorrow and clean it, and I will get some pictures of the carbon build up in the intake. Do you know the starting setting for the idle screw? While I’ve got it off, I’d like to set it up. I want to say that I read somewhere that you run it in all the way and then back it out 3/4 of a turn. May be misremembering though.
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cpt logger
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Posted: 26 July 2022 at 12:23am |
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IIRC, The fuel pressure for the Solex should be 1-1.5 PSI. Yours is at 3 PSI? Maybe the fuel pump is occasionally overpowering the float valve.
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cyates176FA
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Posted: 26 July 2022 at 3:55am |
I'll back the regulator down and see if that improves the situation. I'm assuming that, like most Jeep issues I've dealt with, it's a few small issues feeding into the problem. Maybe the higher pressure is forcing fuel and causing the rich mixture and the excess carbon. I've got a few things that I'm going to check today, just to rule them out before I get into stuff that involves new parts, etc.
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cyates176FA
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Posted: 26 July 2022 at 5:58pm |
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Today's update:
I took the carb off, pulled the jets and blew it out with carb cleaner and compressed air. There wasn't much that came out; but there were a few pieces of junk in the filter screen. I pulled the plugs and cleaned the carbon off of them. As far as the deposits in the intake - there was a decent amount of carbon buildup mixed with some raw fuel. I got some of it out with a paper towel, and also used the shop vac to clean out what loose deposits would come out. I did the same with the plug holes. One thing that stuck out while I was cleaning the carb was that the arm that rests on top of the float looks to have been upside down - at least that's what it looked like compared to the drawings I've seen online. I don't know how much that would play into the idle issues I'm having; but it seems like it could have either kept the float too low/ high or wouldn't interact with the valve at the top of the bowl. Pictures include the carbon fouling on the plugs, the deposits in the intake (not a great pic), and what came out on the rag that I stuck down into the intake. Judging by those deposits, do you think I need to pull and clean the intake? The deposits on the rag were darker than the picture shows, though there may be some rust mixed in with it. Edit: I also adjusted the pressure regulator down from 3 psi to 1.5 psi.    Edited by cyates176FA - 26 July 2022 at 6:06pm |
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Steelyard Blues wrote: