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Unread 12-31-2014, 07:43 PM   #1
Jsadamson1
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CJ sputters and lack of power

My jeep has been sputtering when in second/third and especially 4th. Engine runs great at idle, revs great in neutral. Accelerates great in 1st gear, however when you go to anyother gear and hit the gas it sputters bad. I can smell fuel when it happens. If I slowly advance the gas in second, then there is usually very limited if any sputtering, third kinda works that way, 4th gear works when going down a hill.

Here are the details about the jeep
1984 cj7 151 4cyl. Cleaned out tank, new tank filter, new rubber fuel lines, new fuel filter, rebuilt carb (from someone who knows what to do cause I don't), all vacuum lines as far as I can tell are hooked up and no leaks. NEw spark plugs, cap and rotor. ICM is 4 years old and so is coil. The only thing I know that is missing is the carbon fuel vent canister. The PCM hose is plugged, Carb vent is plugged, Vacuum line is plugged and fuel return line (green) has a small air filer thing on it in attempt to keep water out of it.

Before new carb, I checked plugs, ran it hard as described in another post and then pulled the plugs. They were black. Lots of fuel and exhaust smell. Black suit out the tail pipe. After new carb engine runs very well at idle, feel smoother overall but still sputters. way less fuel smell, way less exhaust smell. I know I am getting closer.

This is my daily driver so I need to make it more reliable. It used to be great running. I dont know what happened.

Thanks in advance
Jason

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Unread 12-31-2014, 09:11 PM   #2
macscal
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Have you checked your timing?

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Unread 01-01-2015, 06:21 AM   #3
Mike Romain
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If the gas tank isn't venting proper, you will get your symptoms. The vent is the charcoal canister that you say is gone. So the line to the gas tank has to be left open to vent the raw gas fumes all over or the gas tank gets a vacuum on it starving it for fuel at speed.
The canister stores the raw gas fumes then purges them into the PCV system when you are at speed. This also helps gas mileage a little by leaning the mix out at speed.
When my canister died, the raw gas fumes were really bad so I got it replaced.

The vent test is to just drive it with the gas cap cracked open to see if it runs right then.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 01-01-2015, 12:45 PM   #4
Jsadamson1
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Drove the jeep with the gas cap off, no difference at all. My next step is to time the jeep. Is there a good write up on timing the 151 4cyl engine? It has all the original components installed.

Thanks again
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Unread 01-01-2015, 07:31 PM   #5
Jsadamson1
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After attempting to time the jeep, the timing mark was set at the very top of the pulley during idle (12 o'clock position) this seems very odd at the indicator is in the 2 o'clock position. I would guess if it was that far out it would not even run.

Also, I was able to get the jeep running better after I found I pinched a fuel line during the carb install. Runs 80% better but still hesitates if I ouch 2nd too fast and in 3rd or 4th I have to limit throttle usage. I know it's either timing, or fuel/air mixture but I don't know what to look at next

Any help is appreciated
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Unread 01-01-2015, 11:34 PM   #6
macscal
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I'm a 258 guy, but your timing (checked with a timing light) should be somewhere in the the area if 8 degrees before top dead center.

This should be checked with the vacuum advance disconnected and plugged....4 cyl guys correct me if I'm wrong.

Also, if your fuel line was pinched/restricted, that may have a lot to do with the condition you were describing.

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Unread 01-02-2015, 12:02 AM   #7
tmshannon
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How about your choke butterfly sucking closed?

Maybe try wiring it open solid and then driving it to see if it cures your problem? Had a buddy in high school with a Bronco that did exactly what you describe.

Travis
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Unread 01-02-2015, 04:25 AM   #8
olddieselcj7
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Have you measured resistance on your plug wires, or replaced your plug wires? After reading your post I did not see where you had mentioned whether you had... Under hard acceleration they could not be carrying enough to fire the plugs correctly, and acting like a plug that is breaking down under load.
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Unread 01-02-2015, 06:48 AM   #9
Mike Romain
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Quote:
Originally Posted by Jsadamson1 View Post
After attempting to time the jeep, the timing mark was set at the very top of the pulley during idle (12 o'clock position) this seems very odd at the indicator is in the 2 o'clock position. I would guess if it was that far out it would not even run.

Also, I was able to get the jeep running better after I found I pinched a fuel line during the carb install. Runs 80% better but still hesitates if I ouch 2nd too fast and in 3rd or 4th I have to limit throttle usage. I know it's either timing, or fuel/air mixture but I don't know what to look at next

Any help is appreciated
What folks forget is unless something internal in the distributor physically breaks, the timing Never changes. You have electronic ignition, no parts to wear down, like old points.
So if it a new issue, it sure isn't the timing being "off".
When you messed with the timing, I hope you put it back like it was. It sounds like you had the vacuum line still attached to the distributor. It needs to be removed and blocked for the test and you need to first find the proper mark on the scale to set it at. I believe it is 12° BTDC. (Before top dead center)
Before you go chasing more things, you really need to verify the timing now.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 01-02-2015, 08:56 AM   #10
Jsadamson1
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Sounds like I needed to disconnect the vac advance. It ran fine and then over time became worse. The timing is probably fine, however who knows what someone previously fixed with timing etc. I will also check the resistance on the wires. They are newer but it's always good to check. What resistance should I be looking for on the plug wires?? I will do that at the same time.

Thanks for all the help so far !!!
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Unread 01-02-2015, 09:42 AM   #11
Mike Romain
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Did we go over spark plug types in the other thread? Having it get worse over time implies something failing. Bosch Platinum plugs act like that. They don't clear fouls well like a copper core does and you foul them every time you start it with the choke on.
Speaking of which, does your choke fully open and stay full open so pushing on it gently with your finger doesn't move it?
Air filter is clean right?
One check for plug wires is to have it tunning in a dark place and spray mist them with water. If you get a light show, they are shot.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 01-02-2015, 10:06 AM   #12
olddieselcj7
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Quote:
Originally Posted by Jsadamson1 View Post
Sounds like I needed to disconnect the vac advance. It ran fine and then over time became worse. The timing is probably fine, however who knows what someone previously fixed with timing etc. I will also check the resistance on the wires. They are newer but it's always good to check. What resistance should I be looking for on the plug wires?? I will do that at the same time.

Thanks for all the help so far !!!
Resistance readings are by the foot, I believe a minimum of 3k ohms to a max. of 15k per foot.
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Unread 01-05-2015, 12:58 PM   #13
Jsadamson1
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Ok, so I ordered new wires (good ones) and decided to go to the original copper plugs just in case. I had just put brand new plugs in and when taking them out found something very interesting that could probably help find the issue. The spark plugs are only used for maybe 50 miles or so. They are in order from cylinder 1-4. First two are black and second look clean. Valve seating issue maybe giving the lack of power?

Ignore any greasy that may have got on the electrodes etc from removing. There is no sign of build up on the plugs other than carbon.

What do you guys think?

image-1760848565.jpg
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Unread 01-05-2015, 01:22 PM   #14
olddieselcj7
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Looks like a couple of cold cylinders.
Have you done a compression test?, or leak down test?, or checked with a vacuum gauge?
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Unread 01-05-2015, 01:25 PM   #15
Matt1981CJ7
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If the same thing happens with new wires, I'd do a compression or leakage test on that engine.

I'm betting cylinders 1 and 2 have bad rings.

Matt
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