Engine running rough, backfiring, misfiring.

My stock 73 CJ5 with 232 I6 starts easy enough but, on cold starts, backfires and begins to run rough after several blocks. Obviously, there is a serious loss of power when this occurs. Once warmed up though, it runs like a top. Plugs, timing, and wires are all good. It is a real mystery. Any thoughts/suggestions? The carb has been rebuilt and all new ignition components are about two years old but have only about 1500 miles on them.

 

Yes.

 

Always starts well, cold or hot.

I did notice a bit of rust on the contact tip of the distributor rotor, sanded it off, but the problem remained. Sometimes it will backfire thru the carb after it's been running for hours. I am perplexed.

 

Running ethanol blended gas?

 

Is the heat riser working properly ????

 

Does it have an EGR valve? Spark CTO?

What do the plugs look like? Tan? White? Black? Sooty or oily?

 

this is my guess aswell.....

 

I have not checked the CTO or EGR. Plugs are whitish in color, no soot. It's just crazy, on a cold start, it'll run like a top for a few blocks, backfire, and then run lousy. Then after about an hour of sitting, runs like a top. Please tell me what to do.

Thanks.

 

Sometimes an old coil will throw weak sparks as its temperature changes.

 

Who stocks a CTO switch for this vehicle?

 

Does a 73 with a 232 have a CTO switch? NAPA shows one for the 304 V8, but I can't find one for a 232 I6.

 

Yes, I expect it does. I would expect your engine to have both a spark CTO and an EGR CTO. They are located on the side of the block, on the driver's side.

I don't have a '73 TSM, so I can't say for certain. Your TSM will tell you for sure.

I'm surprised the 232/258 one is not listed, if one is listed for the V8. They are the same size and shape, and the V8 on will screw in and should work fine. There is a zoo of different part numbers for these (likely why the parts company does not attempt to offer the part) - you may affect the emissions during warm-up by swapping one for another, but I doubt you will notice any difference in performance or driveability.

 

My 73 doesn't have one. But they do have that top gear vacuum advance override thing though.

 

Well, '72 only uses them on the V8s, while '74 uses them on all models. So '73 could go either way. Does your block have the tapped holes for CTOs?

 

My 73 has a CTO but no EGR. Now I just have to find a replacement. The CTO has 3 tubes on it. Any idea where to get one?

 

Here's a link to someone that has a cross-reference chart. It's a start.

http://www.drbob.tqhosting.com/tech/cto.html

Most of the part numbers he's listing can be had at NAPA, AutoZone, or Advance Auto, depending on the brand. I don't think it's about what engine it goes on, it's about the functionality of the switch itself...when does it come on/off and for how long.

 

NAPA has the 220 degree model of the three port, but not the 155 degree model. How much difference does it make?

 

RockAuto has one SMP PVS10 remaining, manufacturer closeout. $13. Act fast ...

You can also check the other part numbers there. www.rockauto.com