I just bought a 1980 cj7 when I got home from Iraq a few weeks ago.

I got a "good deal" on it, figuring it would be easy to fix the one problem that i could find with it. So far I have had no luck.

The Jeep starts fine, and will drive and shift fine for a while, but sooner or later, usually sooner, it will start to "buck" really hard. It starts out bucking once or twice, but will get worse as I keep driving.

In the past, if I killed the engine and then started it right back up I could drive for a while with no problems before it started bucking again

the other day this stopped helping. I was way across town (it was snowing hard and the camaro ss would have been bad news to drive) and I barely made it home. It was so bad it bucked the gear shifter right off where it seats in the shifter housing and I had to crawl home stuck in fourth gear by switching to 4L (I fixed this today)

When it bucks, the RPMs buck up and down with it
I still think it has to be either fuel or spark, but I'm leaning toward spark

So far I have...
1. replaced the carter with a new weber 32/36 carb (I was planning to do this anyway)
2. replaced all plugs and wires
3. replaced distributor cap and rotor
4. replaced coil
5. replaced fuel filter
6. checked for vacuum leaks as well as I can and havent found any (I'm not saying they arent there, but I havent found any)

Right now, I'm thinking about the distributor itself, the fuel pump(I might install an electric anyway since I've heard theyre better at really high altitude here in *** and maybe the timing

any ideas?  

sounds like its starving for fuel,
the pick up could be cloged, vent plugged, fuel pump, check the fuel presure or volume test it, (pull the line off and start it up till the carb runs out of fuel to see how much is being captured in a container. if you don' have access to a presure gadge.) fuel pumps are a common problem as they don't last fo ever, If it was sitting around for years condensation in the fuel tank causes rust and can clog up a new filter and the pick easily.  

I replaced the ignition module just now.
It didnt work.

I'm going to check all the wiring again, and then its down to the tank/fuel pump.

I dont have a pressure gauge, but I might see if I can borrow one.  

Did you ever figure out what was causing this bucking problem?  My 79 cj started doing the same thing today....I thought I would change the fuel filter first, then noticed your thread and wondered if you have any advice to offer at this point.  Thanks in advance.  

the fuel filter is a good start, for sure...if theres particles in it, that'll cause a buck under acceleration.  

when i was working at the chevy dealer we had a couple pups come in with similar problems and found that the distibutor shaft was cracked or broken and we replace whole dist. w/new one and that fixxed prob....just another ave to check....  

Thanks guys.  I got a fuel filter and plan to replace this weekend.  Is it as easy as it looks?  Pull the hoses off the old, push on the new and be done?  That's all the Chilton's manual says.  I thought I read something somewhere about de-pressurizing the fuel system.  Do I need to do this?  

its really easy...take a couple minutes,when you put new filter on it be wise to put screw type clamp  

damn it i didnt finish...put a screw type clamp on because the squeeze type clamps suck, on the same note if you want ultra filtering put two inline w/each other cause you never know whats in the gas these days,i put two inline w/each other on my 74 c10 chevy 350 and no worries  

Cool.  Thanks for info.  

Dang, that was easy.  Took 5 minutes to change the filter.  I test drove about 5 miles and didn't experience any of the symptoms.  Considering how bad the symptoms were prior to the filter change, I'm feeling like the filter solved it.  

sweet! It's amazing what a little restriction can cause..  

hows the patient been over the weekend? any problems? if not, glad its fixxed.  

Been great.  So glad it was cheap and easy.  I have done minor auto stuff over the years, the most challenging thing I've done was change the master cylinder and all of the brake lines on this CJ7.  One of the coolest things about this era of the CJ (mine is a 79) is how easy it is to work on - a great way to learn basics of auto maintenance.  This filter issue cost less than $5 and took less than 10 minutes to fix.

Thanks for tips.  

I wish I had seen this sooner because I had the same problem.  I have the same set up 258 with a weber carb.  All you have to do is clean the carberator.  I bought the rebuild kit and it was simple to do.  If you want a quicker fix, just look at the carb where the fuel line enters the carb you will see a brass nut below where the fuel line goes in.  That nut is a catch for debris in the fuel.  Mine was packed with dirt, so when I would hit a bump that dirt would go into the carb and make it buck.  It was the craziest thing.  Even if you dumped carb cleaner into the bowl it wouldnt fix it.