I have a stock 1989 YJ with the 4.2L 6cyl. The other day I had to pull over because the jeep was missing badly. <img src="/forums/images/graemlins/confused.gif" alt="" /> After I stopped I noticed the muffler was red hot inside (saw thru a crack at the weld joint). Smoke was coming from the muffler. I called a muffler shop and they told me the catalytic converter had gone bad. I then took it to a local muffler shop this past Sat. They replaced the catalytic converter with a ôcoolerö one (one used on a truck). I also had them put on a Flowmaster muffler. Seemed like everything was working OK until the jeep stopped running while at a stoplight. After looking under the hood, I noticed that the air-fuel mixture solenoid on the Carter BBD was broken. Bought a new one and just finished replacing the solenoid tonight. Once again, the jeep seemed to run OK until the engine came to an idle (full open choke). The engine just dies and canÆt start again until the choke closes (partial or all the way).
Could my problem be in the cooler catalytic converter?? Or the Flowmaster?? I thought this since the engine is warm / hot and maybe the new cat is blocking the exhaust flow (back pressure).

Any help would be very useful

4x4david
<img src="/forums/images/graemlins/confused.gif" alt="" />

No it is not the cat! If I han my hands on it I would start with a good tune up. Those carbs can be real meanies. Being in Cal you do not have much choice on what to do..
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

Just had a tuneup couple months back. Just got off the phone with a buddy and he mentioned could be in the idle circuit somewhere. I do a lot of 4x4ing and have three fuel filters (one before the electric fuel pump I just installed, two more just before the carb). The carb is a rebuilt I installed 1 year ago. Leaving in Ca sucks...I tend to tear down the carb tonight and blow/clean all the jets. I have some info from www.off-raod.com/jeep/tech/258bbd.htm. They have some other areas to look at, like the evaporation canister. The metering pins are working. I did a major vacuum hose replacement last year. I keep the jeep in tip-top shape. So when it does not run right I want to make it right.

Thaks for the comments
4x4david

With all that in mind the first I would do is to take the fuel line off of the carb and put a low pressure gauge in at the carb location and check just what the pressure is. Why did you take the factory pump off of there? low or high pressure can cause idle problems..
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

I've heard a lot about those CA emission problems with the Carter. A friend of mine has an 81 CJ7 that when she moved East to SC, she started yanking the CA stuff off. At first it was a nightmare, but with a lot of work and replacing or rerouting the vacuum lines, she has it running quite well. For you to have the red-hot muffler, odds aren't that it is a bad cat converter. They will cause restricted flow and not let the heat even make it to the muffler... so that's out for now. I have seen folks have a bad spark plug or wire that causes this heated condition and bad idle or stalling. See, you might have fuel not burning in a cylinder or two and it is being passed out the exhaust and burns in the exhaust system rather than in the cylinder making things a little hot down the pipe.... The tune up part clicks with this.... Pull your plugs, make sure they look okay and are all gapped properly. When doing this, you can tell if the wires are working at all or not because you will have a plug that don't look like the rest of them. Check to make sure the lead (threaded wire looking thing inside the jacket of the plug wires) makes good contact with the seat (the metal thing that "clicks" on the spark plug on one end and goes down and makes contact inside the cap) inside the boot on both the plug end and the dist cap end....

Okay, thats for the red muffler thing....

Make sure all the vacuum lines are hooked up where they are intended to. A combination of the web and a Chilton book will help this test....
web page with great stuff on it....
click around that site and you will find diagrams and some good write ups....
Okay, that aside, try a test that will help figure out part of a vacuum problem.... pull the gas cap off and try to run her. One of the vacuum lines runs off the evap. canister to the fuel tank. Oddly enough, this may help in the troubleshooting. Next would be doing a test on the canister to see if it is clogged, if it is functioning properly, if it is purging or whatever.

Just some thoughts.... Good luck and keep us posted as to what you find and what cures this.

Happy Jeeping!

Thanks for all the good info...Your thought are the same as mine...At least after talking to some guys at work...I pulled all the plugs tonight and the tips look light brown with a lot of crud around the tip. Replaced all. I made sure that the plug wires made the 'click" sound. All plugs looked the same so I know they are all firing. Thanks for the web site link. I am looking at it now. I will keep you up to date.
What does the light brown with a lot of brown carbon build up mean....too lean....too rich..


4x4david

Another thought....Would a bad O2 sensor cause this problem. I mean, not send the correct data to the stepper motor via the computer?

Just brainstorming....I was reading about the Decel Valve on the web. It talkes about that if this valve is stuck open, the result would be a massive air leak into the manifold, driving the MCU crazy. Would this cause the engine to warm up fine then after idling for a while make the engine die?

I don't have a Haynes book in front of me, but in the front or back of them they have little colored pictures that explain that stuff. I'm sure that sounds like an improper mix setting, but which way, I don't really know off the top of my head. Problem that I normally run into is white on the electrode insulator and black crud everywhere else, not the brown....

Little more history what led to theis adventure. Last month I was in the Death Valley area 4x4ing, when all the problems started. I had noticed that the jeep was running rough while running down the black top. While driving at hwy speed I could smell something burning. I pulled over to see if there was an unusual oil leak-none. While on the trail the jeep would backfire, sput / spit while underload (going uphill in 4x4 low, 1st gear). Very consistant. Had trouble starting after taking a 15 min break for lunch. I first thought it was a vabor lock (I believe I had vabor lock while hard wheeling in last summer, temp peaked out). This is why I installed an electric fuel pump inline with the mechanical pump. Mech pump is sill working OK. Electric fuel pump..backup. Anyway hope this helps with the dianostic.