1979 AMC 304 Rough idle.

[Hedgehog]

I capped my PCV valve port for the Charcoal Canister. More and more I think you have a carb problem, what it is I have no idea. I have heard that some 2100's develop internal cracks that are difficult to find.

 

[jafo]

I capped my PCV valve port for the Charcoal Canister. More and more I think you have a carb problem, what it is I have no idea. I have heard that some 2100's develop internal cracks that are difficult to find.

That wouldn't surprise at this point. What gets me is it's intermittent. One time it take off great down the road out of the driveway snd then next time it will barely make.it down the street. I drive all over town the other day and it did great until I took off going up a hill. It didn't do any of this before I did the suspension. Not blaming the suspension work, just a time table. Maybe the bigger tires enhanced the problem being it's put the engine under more load most the time.

I just still have this feeling the EGR valve sticking has some of the blame. It felt froze when I checked it and then it stuck open after it moved then kind of freed up but still sticks. It never operated smoothly. Also I checked it with a vacuum pump and the diaphragm is bad, it won't move. I know EGRs can cause vacuum leak symptoms too and that what it seems like it has. I would swap it with a new one, but no one in town has a friggin EGR for this thing. It will be at least 3 days they have to order one. I haven't tried Autozone though.

You capped your PCV? How does your engine vent? I get the charcoal cannister and I may try that.

 

[jafo]

Well, I repaired or hope that I repaired the exhaust back pressure sensor for the EGR valve. I also did a smear job with some good sealant on the EGR diaphragm and freed up the pintle so it doesn't stick anymore. Keep in mind this is for amusement. I ordered a new EGR and won't get it until Wednesday. No one in the kansas city area or within 2 hrs drive had one. Nearest was Springfield Missouri. Wow. But anyway, I fully expect this NOT to work, but hey, gotta try it. So here goes nothin.

Oh and I have a new possibility to explore also. The gas tank. I thought maybe a restriction in the line or dirty strainer. This jeep has sat for awhile and hadn't really been drove meaning old gas and carbuncles in the tank. New fresh gas may have loosened something up and it would be an intermittent thing too. I have ran into this on amy dads boat that sat for a long period with no stabilizer in the fuel.

 

[007]

Sadly you've done great work here and not gotten results. So don't forget your efforts on this are quite respectable.

You could strap a can on your front bumper or somewhere in the passenger area and run a pickup line to it to rule a tank issue in or out?


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[jafo]

I found something. I kept hearing this exhaust leak towards the back ofbthe engine. Assume it was the y-pipe flange passenger side leaking. It does leak a little. But I have traced the sound to a round hole top of the backside of the block just below where the intake and block center section meet. What the heck is this and what is supposed to be in the hole? Expansion plug or thread type plug? I can stick my finger in the hole and plug it, there is not much back pressure to it. ??????? Crankcase vent? I have to plug it. It's like right below the EGR valve.

 

[Hedgehog]

No, I didn't cap the PCV, Was afraid there would be confusion. I capped the vacuum vent that is part of the PCV that purges the Charcoal Canister. Definitely change out your EGR valve. There are several different types, some are universal. The one I purchased is a universal unit, it comes with different size ports, a set of disks with different size holes in it. Unfortunately non of the ones in the kit were listed for my 360. Pay the price for the correct one for your application. They aren't inexpensive. But they are also relatively easy to work on.

Some guys like to cap the ERG valve right off. The function is counter intuitive, by adding exhaust gas to the intake the engine runs cooler. Doesn't make sense to me, but the pointy heads say it works. So, I'm not convinced it is a good idea to cap the system off. You could try it temporarily to see if it makes a difference.

This started with a suspension upgrade? I am not a believer in coincidences. You say that you went with bigger tires. Sorry but I don't remember, what size are your new tires? ....... Forgive me, but what oil/grease are you running in your Transmission ? Cold thick oil/grease is hard to push around in a Transmission .

Edit: you ere typing while I was typing. A hole? Is it a drilled hole or some sort of broken piece?

 

[jafo]

Sadly you've done great work here and not gotten results. So don't forget your efforts on this are quite respectable.

You could strap a can on your front bumper or somewhere in the passenger area and run a pickup line to it to rule a tank issue in or out?


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Ah. That is an exellent idea! When I get to that point, I will try that.

And thanks.

 

[Hedgehog]

At this point you know what I'd try to do if I were you? Take a break from the repairs. Let your mine rest for a while. Walk away for a week. I have been amazed at how much easier it can be to find a problem with a fresh rested mind.

 

[jafo]

No, I didn't cap the PCV, Was afraid there would be confusion. I capped the vacuum vent that is part of the PCV that purges the Charcoal Canister. Definitely change out your EGR valve. There are several different types, some are universal. The one I purchased is a universal unit, it comes with different size ports, a set of disks with different size holes in it. Unfortunately non of the ones in the kit were listed for my 360. Pay the price for the correct one for your application. They aren't inexpensive. But they are also relatively easy to work on.

Some guys like to cap the ERG valve right off. The function is counter intuitive, by adding exhaust gas to the intake the engine runs cooler. Doesn't make sense to me, but the pointy heads say it works. So, I'm not convinced it is a good idea to cap the system off. You could try it temporarily to see if it makes a difference.

This started with a suspension upgrade? I am not a believer in coincidences. You say that you went with bigger tires. Sorry but I don't remember, what size are your new tires? ....... Forgive me, but what oil/grease are you running in your Transmission ? Cold thick oil/grease is hard to push around in a Transmission .

Pointy heads.....I like it. LOL.

I went with the 4" lift and 33x12.5x15 tires. Much larger diameter. I don't think the lift itself did it, itcs a timetable thing. It was after the bigger tires went on the problem really showed up.

I got this hole on the top baskside of the block kicking out exhaust. Cold, it pushes exhaust out. Now that it has warmed up, you can just lay your finger over the hole and you can feel a slight sucking in. Not alot, but itcs there. The exhaust noise goes away after warm up also. So that tells me it's sucking air in after warmed up. If itcs part of the EGR circuit, this might be my vacuum leak.

 

[jafo]

At this point you know what I'd try to do if I were you? Take a break from the repairs. Let your mine rest for a while. Walk away for a week. I have been amazed at how much easier it can be to find a problem with a fresh rested mind.

Yes. Sound advice. Just not in my nature. I like to push through problems. I may say things like "I give up". In reality what I'm saying is "I'm walking away for five minutes and I'll be back". My wife hates this about me. Believe it or not. When I do something, I'm all in. I won't stop until I get the desired results.

The day I did the intake and sounded whipped? I was for about a half hour. I went back out and put it all back together except the anitfreeze. It's my curse I guess.

When I have a bunch of great people like you guysn it spurrs me on even more. I like this stuff. "Embrace the suck"! What I refer to when things go bad.

 

[jafo]

It is the back of the intake just below the EGR. I just need to figure out what goes in there.

Ok updating, it's a threaded plug. A big one. I don't think I have an allen that big let alone a plug that big. It has a hole in it.

Temporarily plugged for now. That thing will need special attention to get it out. Probably heat and I can't do that with it on the engine. Wish I would have noriced it when I had the intake off.

 

[jafo]

Ok I let the plug set up and no longer leaking. It seems to run fine. No coughing or misfiring. The carb still feels wrong. Could these carbs be undersized for the engine or is it just a jetting thing? Can you get a different size power valve for these motorcraft carbs?

 

[jafo]

I tried opening the carb on up and results in no more power, and hint on a cut out up top. Only in 3rd gear on a hill. So maybe it's a lean pop. I'll look into the fuel tank next weekend. Right now I'll take hedg's advice and take a week off and just enjoy driving it.

 

[Lumpy Grits]

Take the gas cap off of the tank, and take it for a drive.
LG

 

[jafo]

Take the gas cap off of the tank, and take it for a drive.
LG

I just filled it up today and noticed the gasket was trashed. But yeh good idea.

 

[Torxhead]

I believe earlier you did mention that you installed new spark plugs and had rebuilt the carb. This would be a good time to inspect the spark plugs to check for proper fuel burn. You could check them against a spark plug chart on the internet.

 

[007]

Agreed. I'm so glad you've found some progress. Good work!


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[jafo]

Take the gas cap off of the tank, and take it for a drive.
LG

Tried this tonight. Didn't net anything. I did find out I lost the rubber gasket somewhere though. I think it fell off, it was dry rotted anyways. I just made a new one.

To me it's down to the EGR, and fuel system. Might try what was suggested earlier. I have a couple plastic small gas cans that I can use to try running gas out of it instead of the fuel tank and go from there.

 

[jafo]

I believe earlier you did mention that you installed new spark plugs and had rebuilt the carb. This would be a good time to inspect the spark plugs to check for proper fuel burn. You could check them against a spark plug chart on the internet.

I'm going to try and drive it do work this week and get some more miles on them. I can do a quick check. The old plugs I pulled out looked good. They had the nice light brown color no deposits or build up. I'm curious about the new plugs to see what they look like. Just want to get a few more miles on them.

 

[jafo]

Agreed. I'm so glad you've found some progress. Good work!


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Thanks. I never thought I'd have this much trouble diagnosing something. We're not there yet but close. Just got to eliminate a few more things. It's an old jeep that hasn't had much attention paid to it and it's showing with all the work. I've seriously doubted myself a lot. I appreciate all the help and ideas everyone here has offered and donated their time to help a jeep newby out.

This thing is a blast to drive. I've always wanted a CJ Jeep. I didn't care which one. I like them all. There's just something cool about going old school. I like the new jeeps, but one's almost like another. At least with the old school jeeps, there's not a bunch around and they're all business. No creature comforts, just all business.