Engine running rough, backfiring, misfiring.

The temperature level makes a difference, the whole point is that the switch allows vacuum, or switches vacuum source, or stops vacuum at certain temps. If you buy the wrong switch then your vacuum will be applied at the wrong time and will possibly make your engine run rough...kind of like now.

Two more useful links...

The '72 TSM
http://trailforge.com/cms/index.php?option=com_content&task=view&id=24&Itemid=30

And the '74 TSM
http://oljeep.com/edge_74_tsm.html

 

Just a plug, but as far as i know my jeep was original.

 

Thanks to all for your help. I broke down and took it to a shop here in Austin, Texas that specializes in Jeeps. We have determined the CTO switch is bad as well as the coil. The switch has been ordered and I'm picking up a NAPA coil tomorrow. Jenny B (the Jeep) should be healthy again very soon. Thanks again.

 

Ok, the mystery continues. A NAPA coil was added today and I ran a vacuum line from the manifold to the distributor vacuum advance while I'm waiting on the CTO switch to arrive. The thing runs like crap. Misses and backfires under a load. What gives?

 

plugs whitish? sounds lean id guess carb.....the advance goes to ported vacuum only gets vac when throttle open. manifold vac is giving the opposite...

 

Try replacing the Ignition Control Module.

 

I don't think I have an ignition control module. It has points/condenser, not electronic ignition. Please tell me if I am wrong.

Question though, does a backfire through the carb do any damage to the carb?

 

Interesting, I am not sure of the answer to that questions, however if you are still using points you may consider upgrading to a more modern distributor system. This may solve your problem.

 

First year for electronic ignition in Jeeps was 1975. All the '73 models had point and condenser. SO no ignition module.

Only the 2-barrel V8 carbs can be damaged by backfire, AFAIK. You should be ok.

 

How many miles does this engine have? Enough so that the timing chain is waorn out, and it jumped time? Can you check the timing?

Generally when you get a problem with the way the engine runs, with no new clanking or banging, and the compression is good, it has to be something to do with fuel delivery or spark.

So, initially I'd check the timing and run a compression test, just to see where we were. Both of these tests are easy and the equipment is cheap.

 

This being said, I had the same problem. Went to an h.e.i. dist. and solved my problem. But, mine was a 75 with a prestolite ignition. very trouble prone.

 

Thanks for all the responses. The Jeep only has 15,500 miles and ran like a top until recently. I had the carb rebuilt last spring and the mixture may have been set a little lean. I found a new cto switch and am installing it tomorrow. After it is installed, I'll check the timing and have someone check the carb mixture. I have thought about adding the electronic distributor but would prefer to keep it stock. This experience is changing my mind. Is there a way to convert the factory distributor to an electronic device?

 

From your posts it seems like it Idles ok. Try disconnecting the vac advance. Any improvement? If not I suspect your problem lies with the carb, when was last time it was rebuilt?

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pertronix ignition fits under a stock cap