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Unread 12-18-2011, 12:17 PM   #61
oldtime_ironman
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Every auto that I've ever seen will drop about 200 RPM. More than that would be a worry. I think yer real close now, most likely you'll have to dance back and forth between timing and fine-tuning the carb now. Probably I would advance the timing just a hair - maybe one degree. Then tweak the idle speed back down with the carb since the timing will affect the speed. Let's wat and see what Old4x says.
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Unread 12-18-2011, 02:41 PM   #62
Old4X
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From one of your earlier posts, I would look real close at your snap-on coil wiring connection. Those will loosen up over time and cause intermittent problems. Try to tighten the connectors in the snap on piece, or wrap some rinfoil around each of the the coil studs and see if the problem goes away.

Also, did you ever get a vacuum gauge? This is where you can really start using it. It can help spot bad valve seating, as well as help with final carb tuning.

Try upping the advance to 10 degrees and see what that does.

Sounds like you are closing in on it.
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Unread 12-18-2011, 02:43 PM   #63
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One other thing, what spark plugs are you running, and what are they set to?
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Unread 12-18-2011, 03:54 PM   #64
JeepJon15
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No gauge yet, but now that i'm somewhere where i can start tuning it in ill pick one up tomorrow. Timing is set at about 10* now, it did reduce the stalling issue but it does still happen. My coil is a replacement from autozone, i think its the only kind they had in stock for a 4.2 yj. The connection looks pretty good, but maybe ill try the foil and see if i can tell a difference. My plugs are also from autozone, i cant remember what brand but they looked them up on their computer. I did not set the gap on them, is that important for this engine?
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Unread 12-18-2011, 04:17 PM   #65
oldtime_ironman
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Quote:
Originally Posted by JeepJon15 View Post
No gauge yet, but now that i'm somewhere where i can start tuning it in ill pick one up tomorrow. Timing is set at about 10* now, it did reduce the stalling issue but it does still happen. My coil is a replacement from autozone, i think its the only kind they had in stock for a 4.2 yj. The connection looks pretty good, but maybe ill try the foil and see if i can tell a difference. My plugs are also from autozone, i cant remember what brand but they looked them up on their computer. I did not set the gap on them, is that important for this engine?
Um, yes setting the plug gap is important. You would be amazed how many of them come out of the box being way off. They aren't meant to be even close when they are manufactured - you are supposed to set them for whatever kinda vehicle you have. So I would urge you to get a fresh set of plugs and gap them properly, same time you get the vacuum gauge.
.

Last edited by oldtime_ironman; 12-18-2011 at 04:18 PM.. Reason: sp
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Unread 12-18-2011, 05:55 PM   #66
JeepJon15
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Any specific spark plug work well for the 4.2 l6? I'd like to just pick some up at autozone.
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Unread 12-18-2011, 06:07 PM   #67
oldtime_ironman
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Quote:
Originally Posted by JeepJon15 View Post
Any specific spark plug work well for the 4.2 l6? I'd like to just pick some up at autozone.
Haynes calls for Champion RC9YC... I usually just get whatevers on sale, the equivalent. My autozone usually has Autolite platinums for $2 each. According to Haynes, the gap should be 033 to 038, so pick an average figure of 035 and you should be good to go.
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Unread 12-18-2011, 07:16 PM   #68
Old4X
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Many here have had problems with the exotic plugs. Plain Autolite truck plugs (copper something or other, don't recall the name) are what works best far and away. For some reason I always use Champions in my GM engines, no problems there either.

As O_I mentioned, gapping the plugs is very important. Your spark voltage changes as your plug gap changes, so you could get to the point of uneven firing from just the plugs.

Also, getting bad plugs out of the box isn't uncommon. I got a bad one and knew that was causing ignition breakdown. Changed one plug at a time till I found it. It was partially firing, but arcing internally as rpms increased. Caused a definate skip under acceleration, but idle was OK.

A bad plug wire can do the same thing.

You may be down on compression on a cylinder. That will cause uneven idle, but seems to go away once RPMs get up. A compression check may be in order if carb tuning and ignition work doesn't get the skip to go away.
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Unread 12-18-2011, 08:08 PM   #69
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Well... i planned on driving the jeep to work tomorrow morning so i just let her warm up in the driveway for 10 minutes so i could go get some gas. Fired up good and strong, ran a little strange at first, but pretty strong. Chalked the roughness of the idle up to sitting in the same spot for pretty much 3 weeks, need to get some fresh gas in.

I noticed when i pushed the gas pedal, the headlights were getting brighter. Also, seemed to lose power right after i let off the gas then would immediately recover. Almost like it didnt happen, but i'm pretty sure it did. Anyway, i pull out of the driveway, onto a country road (55mph) and she dies... I go to start back up and its not happening. I only try it 3 times and the battery clearly doesnt have enough juice left to try anymore. (may also be emitting a little more exhaust than normal)

I dont have a trickle charger here at the moment, and the battery has died a time or two while working on it. I was low on gas, so maybe that could cause the rough running when i started it. I put a gallon in and was going to jump it again, but i kinda said screw it because its late. I may go out and try... but what do you all think this problem is? Lights still bright, heater will still run.

I'm not sure if im at the point where this is getting funny, or its not funny anymore. I drove all summer and all i had to replace was a couple ujoints. Now that the weather isnt as forgiving, queue the breakdowns.

*I let the engine run 3 or 4 times today for 10 minutes at a time just to make sure it was good to go. Each time before just now it ran well. I also took it for a couple mile test drive with no problems.
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Unread 12-18-2011, 08:59 PM   #70
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The losing power when letting off the gas still sounds like carb related to me. Ignition problems are normally worse under power and when accelerating.

Dimming lights is a sign of a battery that needs charging, but if all battery and alternator connections are good, it shouldn't cause stalling.
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Unread 12-18-2011, 09:25 PM   #71
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I'm guessing the actual stall was from whatever is causing the hickup in the engine. Would a lean or rich mixture cause the "carb related" problem you mentioned? If so, which mixture specifically? I think i have it running on the rich side right now.

My positive connection on my battery could use some cleaning, i just went out and checked. Is it a bad idea on these jeeps to take off the positive battery terminal while its running to test the alternator? I've read it can be dangerous for you and your car, but have also read if youre not careless its okay to do. The battery is getting a little old, but rent is due soon and i'd rather not buy one just yet if i dont need to.

I'll clean the positive terminal and see if i get any change. I'm sure a trickle charger would help too, so ill see if i can borrow a friend's.
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Unread 12-18-2011, 10:01 PM   #72
Old4X
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Not good to pull the battery cable off when running. For 10 bucks you can get a multi meter and test to see if the alternator is charging. (every Jeep owner should have a multi-meter). Also not good to pull a spark wire to check for bad wire or plug while running. Use a grounding wire to do that (so the high voltage has somewhere to go rather than arc and burn ignition components.).

If it is rich enough to stall out, you should see visible smoke out the tailpipe. A rich running engine has a deep tone to the exhaust. Lean has a splashy sound. Hesitating when "gassinon it" is usually a sighn it is lean (especially if it pops back through the carb).

Pulling the plugs usually helps confirm rich/lean question. Rich will have blackened plugs, lean no sign of blackening (or very little in center 2 plugs).

edit to add: I hear you on not wanting to buy a battery. I am running a lawn mower battery in my farm truck right now. Chevy 350 4 barrel and it hits before one complete rev of the engine when starting. Good thing, cause that is all the umph those lawn mower batteries have!
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Unread 12-19-2011, 06:39 AM   #73
oldtime_ironman
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I would clean up the batt terminals all shiny and throw on a fresh pair of termainal clamps. Then test again, the lights shouldn't change.
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Unread 12-19-2011, 11:55 AM   #74
JeepJon15
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Just got home from work. Thanks for the replies guys.

I'm going to autozone soon to get
1) vacuum gauge
2) battery tested (and free charge)
3) A sparkplug gap setting tool, and some plugs
4) some fresh battery terminal clamps.

Like i said, there seemed to be more exhaust than normal, but i dont know if there was smoke. I have the mixture screws between 2 1/4 and 2 1/2 turns out right now. From your feedback, the symptoms say lean, but with the screws backed up so much wouldnt that say rich? I guess i'll know better once i get the vacuum gauge.

I'll report back once i know more. Thanks again.
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Unread 12-19-2011, 01:27 PM   #75
JeepJon15
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Went to autozone for the goods. First thing i did was get my battery tested, the guy said it was a bad battery. Damn it. I was under the impression you were to drop the battery off and pick it up a while later after they charge and test it. He just hooked the machine right up to it and tested it. Is this because it wasnt completely dead?

Shopping around for batteries now. Probably going to get a cheapo for now and buy a better one when i'm not spending so much money on other parts/other things. Hoping it was just the battery's time, and it didn't die from another faulty part.
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