Rough idle in Gear

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Money Pit

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I drove the car for about 10 min. After I got home, when the car is in gear, the idle is rough, smoothes out and idles rough, like it's not getting gas. The engine idles perfectly in park. When I drive it, it runs fine. It's a 1970 225 with a Holley 1920. In the last week, I relocated the fuel line (replace the metal line with fuel injection hose) and installed a metal fuel filter. The plugs, cap, rotor, wires are new. I have a pertonix conversion. I also checked the fuel pick up. the tank and fuel pump have just been replaced. The timing is fine. I was having stalling problems previous to this problem. The stalling problem has been resolved. I'm new to slant sixes, but not to MOPARs. I never had issues like this with my V8's. I have a lot to learn. Thanks in advance.
 
I'll have to pull the plugs tomorrow. I didn't think about pulling the plugs since it idles so well in park. Thanks
 
im going to guess that a piece of dirt or garbage has gotten hung up in the idle circuit causing it to run a bit lean.in park there is no struggle to idle but in drive it would struggle and idle kind of choppy
 
Money Pit said:
Yes. It's one problem after another.
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It may be one problem after another but they should all and I mean all be easily fixed and cheaply. If anyone tells you something on that cars expensive I mean anything over $100 they lost their mind.
 
the wall said:
im going to guess that a piece of dirt or garbage has gotten hung up in the idle circuit causing it to run a bit lean.in park there is no struggle to idle but in drive it would struggle and idle kind of choppy
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I've definitely had this problem before where a piece of trash gets caught in the float needle. Funny enough it was a piece of the Junkie cheap fuel filter! LOL
Honestly though I'm not sure this is carburetor related.
I don't have a whole lot of experience with slant sixes, but any time I've ever did a simple valve lash adjustment it's always been a night and day difference. No matter what your current problem is.
 
Oh yeah and when that piece of trash got caught in there I mean it was choking smoke like nobody's business. Or I was getting at with that whole vacuum advance thing and it was just spitballing mind you I was thinking about maybe the timing getting a little out of whack through the vacuum advance at idle? Again just spitballing with that idea. Or just a plain old vacuum leak and it's sucking air somewhere and not getting enough fuel while it's idling, but when it goes into gear and idles down a bit it's getting too much air? Again spitballing. But I like cheap easy fixes...
As in something just popped off and you got to put it back on and everything is going to go back to normal!
 
j par said:
I've definitely had this problem before where a piece of trash gets caught in the float needle. Funny enough it was a piece of the Junkie cheap fuel filter! LOL
Honestly though I'm not sure this is carburetor related.
I don't have a whole lot of experience with slant sixes, but any time I've ever did a simple valve lash adjustment it's always been a night and day difference. No matter what your current problem is.
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this very well could be it but i dont think it would all of a sudden happen with valve lash. that would be gradual in my opinion but you might have it. im working from the just happened new angle

so that being typed look for a air leak of some kind like a pcv hose or leaking power brake booster or hose
 
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the wall said:
this very well could be it but i dont think it would all of a sudden happen with valve lash. that would be gradual in my opinion but you might have it. im working from the just happened new angle

so that being typed look for a air leak of some kind like a pvc hose or leaking power brake booster or hose
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I totally agree with you and your exact angle. I just think of things backwards. It could be something like my dyslexia.
But I do really really really want to drive home how much every time I've done a valve lash adjustment on one of those in any situation it's helped. But agreed unlikely the direct cause butt I have had a 273 with those stupid adjusters which actually now that I think about it don't the slant six have those binding adjusters on the rocker arms? I've had one of those come loose and get a bad idle.
 
Money Pit said:
I drove the car for about 10 min. After I got home, when the car is in gear, the idle is rough, smoothes out and idles rough, like it's not getting gas. The engine idles perfectly in park. When I drive it, it runs fine. It's a 1970 225 with a Holley 1920. In the last week, I relocated the fuel line (replace the metal line with fuel injection hose) and installed a metal fuel filter. The plugs, cap, rotor, wires are new. I have a pertonix conversion. I also checked the fuel pick up. the tank and fuel pump have just been replaced. The timing is fine. I was having stalling problems previous to this problem. The stalling problem has been resolved. I'm new to slant sixes, but not to MOPARs. I never had issues like this with my V8's. I have a lot to learn. Thanks in advance.
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The ONLY possible way that /6 could be a money pit is if you're not doing the simple stuff yourself. Witch is everything. The technology is 50 years old and simple. The problem is one thing can't be fixed every year for 50 years and expected to be like new. Pretty much if you get a 50 year old car that somebody's just worn down to a nub you have to change everything to make it drive like new again. the important idea here is to change the important things first and continue to change things more quickly than slowly. Or you have that same thing where things are wearing out before the other things are even getting fixed. And then it seems like a money pit need constantly chasing and fixing things. You need to fix it and get ahead of things and start doing preventive maintenance. As in after you get this fixed do some other stuff like the free valve adjustment or just buying some new hoses or things like that keep ahead of it don't just drive the crap out of it till something happens and then say it's a piece of junk. Just saying, grain of salt intended...
 
j par said:
The ONLY possible way that /6 could be a money pit is if you're not doing the simple stuff yourself. Witch is everything. The technology is 50 years old and simple. The problem is one thing can't be fixed every year for 50 years and expected to be like new. Pretty much if you get a 50 year old car that somebody's just worn down to a nub you have to change everything to make it drive like new again. the important idea here is to change the important things first and continue to change things more quickly than slowly. Or you have that same thing where things are wearing out before the other things are even getting fixed. And then it seems like a money pit need constantly chasing and fixing things. You need to fix it and get ahead of things and start doing preventive maintenance. As in after you get this fixed do some other stuff like the free valve adjustment or just buying some new hoses or things like that keep ahead of it don't just drive the crap out of it till something happens and then say it's a piece of junk. Just saying, grain of salt intended...
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I did the valve adjustment about 2 weeks ago, when I was having problems stalling. I checked for vacuum leaks,
the wall said:
this very well could be it but i dont think it would all of a sudden happen with valve lash. that would be gradual in my opinion but you might have it. im working from the just happened new angle

so that being typed look for a air leak of some kind like a pcv hose or leaking power brake booster or hose
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No leaks. I'll look and see if any junk got into the carb. Thanks
 
I had a good friend with a Volare Station Wagon /6, and the same thing (pretty much) was happening to him, and he asked me to take a look at it. I took the air cleaner off, thinking I might need to adjust the carb. When I touched the carb, it kind of wiggled a bit. somehow, some screws that went up from the bottom had worked loose, and they held the carb together. I had only ever worked on 4 BBL carbs that were taken apart with screws from the top. So I took the carb off, tightened a few screws and it ran great. It is worth checking.
 
Money Pit said:
I checked the timing, it's set 5 BTDC with the vacuum line off and plugged. Now that's useful information.
It doesn't wander when I rev the engine. But what means this
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I mean, my wife wanders in the mall. A dear wanders in the forest. And the Israelites wandered in the desert for 40 years.
But what does this mean; "It doesn't wander when I rev the engine"?
I mean you took the time to type it, so it must be important.


Since the engine only idles rough in gear, I'll guess the problem is LOAD related. So the first thing to do is get a vacuum gauge on it and a tachometer. So we can see the actual load. You will need to report the approximate average rpm both in gear, and in N/P.And the vacuum readings that go with those rpms. That will tell us a lot.
Anything else I could say is pure speculation.
 
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AJ/FormS said:
I mean, my wife wanders in the mall. A dear wanders in the forest. And the Israelites wandered in the desert for 40 years.
But what does this mean; "It doesn't wander when I rev the engine"?
I mean you took the time to type it, so it must be important.


Since the engine only idles rough in gear, I'll guess the problem is LOAD related. So the first thing to do is get a vacuum gauge on it and a tachometer. So we can see the actual load. You will need to report the approximate average rpm both in gear, and in N/P.And the vacuum readings that go with those rpms. That will tell us a lot.
Anything else I could say is pure speculation.
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Sorry, the timing marks don't jump all over the place at idle or when I rev the engine. Is there a "best" place to connect the vaccuum guage?
 
harrisonm said:
I had a good friend with a Volare Station Wagon /6, and the same thing (pretty much) was happening to him, and he asked me to take a look at it. I took the air cleaner off, thinking I might need to adjust the carb. When I touched the carb, it kind of wiggled a bit. somehow, some screws that went up from the bottom had worked loose, and they held the carb together. I had only ever worked on 4 BBL carbs that were taken apart with screws from the top. So I took the carb off, tightened a few screws and it ran great. It is worth checking.
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When the car was stalling I had a similar problem. The nuts that secure the carb to the manifold were working loose. After a little lock-tite that problem was solved. The body of the Holley doesn't come apart. Everything is accessed through the float bowl. Thanks
 
AJ/FormS said:
I mean, my wife wanders in the mall. A dear wanders in the forest. And the Israelites wandered in the desert for 40 years.
But what does this mean; "It doesn't wander when I rev the engine"?
I mean you took the time to type it, so it must be important.


Since the engine only idles rough in gear, I'll guess the problem is LOAD related. So the first thing to do is get a vacuum gauge on it and a tachometer. So we can see the actual load. You will need to report the approximate average rpm both in gear, and in N/P.And the vacuum readings that go with those rpms. That will tell us a lot.
Anything else I could say is pure speculation.
Click to expand...
If there is an air leak, would it run rough, smooth out and run rough again. Thanks
 
Money Pit said:
If there is an air leak, WOULD it run rough, smooth out and run rough again? I don't see how, so IMO, NO Thanks
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I'm not looking for an air leak, cuz you said the only time it runs rough is stopped, and idling in gear, I suppose like at a stoplite; and at this time the idle-timing is fixed at 5*Btdc and not wandering.(got-it lol).
So, in my opinion, this has nothing to do with timing, nor with a vacuum leak.
I'm suspecting the TC
or the powervalve,
or a combination.
with a possible problem in the low-speed circuit.
The vacuum to rpm readings will help me formulate an opinion as to what test to do next.
For instance; a 50 rpm drop between N/P and in gear tells me the TC is fine. And if the vacuum reading varies only a little, then I'll stop thinking about the TC.
But if the vacuum is low to start with, and then drops even lower, perhaps low enough to open the power valve, then the rough running is due to the leaking PV, but that PV is not the root cause, which would be the low vacuum reading or a bad TC.
So then we have to do a compression test...... because you said you already reset the valve-lash. Had you not said that,then the valve lash would have been the first thing on my mind.
And if the compression test is good, then I have to assume you did a good job on the lashing. But if not, then we have to do a LeakDown test to see if any valves are leaking......which leads to a valve re-lash. And that will lead to other tests.

The best place to plumb the vacuum line to, is anywhere on the intake manifold. Close to the firewall there is usually a vacuum-tree. If not, you can disconnect the choke pull-off and tap in there. Just don't use the spark-port that runs to the vacuum-advance cam.
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BTW, talking about the Vcan, with the engine idling in N/P, suck on that line; the rpm should go up, maybe as much as 100 rpm after multiple sucks. That proves both the can and the line are good. But if the rpm does not go up, then put the timing lite on and verify the 5*. Then switch the vacuum line over to the choke pull-off port. This should add about 9 to 19* of advance. If zero, then either the line or the can is bad, so check the line next. If the line is good then the can is bad. If the line is bad, replace it and retest. This has nothing to do with your problem.... unless the Vcan is currently connected to full manifold vacuum.......lol.I just thought this would be a good time to mention this.
 
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