Ah the rain! I love the rain.  Bringing a nasty drought to an end and helping to oxidize virgin steel into lumps of beautifully jagged metal so that I can get it for free. Welcome once again rustlovers to The Free Model T.

     Here in San Diego we have been absolutely battered by storms for the last few weeks leaving many a floorboard soggy due to old weatherstripping and even causing a leak in my garage. No good! This time I did not let the rain slow me down.

     My car hauling trailer has been neglected for many years and needed some serious love. The driver’s side fender is removable for easy exit after driving onto the trailer but on the last desert trip it actually broke off. 

     Inspecting the trailer I found many cracked welds and other things in need of attention and I’m ashamed to admit that I’ve never checked the brakes or packed the bearings. So I did. I also welded all the areas in need of attention, welded on a new tongue jack that has a pin lock so I can swing it out of the way, changed the brake shoes and the trailer break away kit and installed all new lights. The trailer is good to go and I did all of the welding outdoors in the rain.

     Now that the trailer is roadworthy I had to smog my ’95 Jeep ZJ “The Summer Project”. Since the distributor has just been changed and I have only 400 miles on a fresh engine, emission testing should be a breeze. Except it FAILED!

     I took the ZJ (I like to think that it stands for “Zombie Jeep” since I brought it back from the dead) down to my favorite smog shop and it failed on high NOx. I plugged my stats into an online lambda calculator and found my catalytic converter to only be functioning at 36%. This was shocking to me because I’ve already gone through this with THIS JEEP!

      Flashback to 2 years ago. Jeep fails on high NOx, well OBVIOUSLY! When I got it it had a bad oxygen sensor, a massively cracked exhaust manifold and was overheating AND misfiring. Of course the catalyst was bad!  I installed a premium   Magnaflow  catalytic converter and a new oxygen sensor. I was and still am a HUGE fan of their products and they are the only aftermarket cat manufacturer that I will install. 

     Flash forward to the present. What went wrong? Who killed the cat? In short; I don’t know. But I will. The two most common cat killing culprits are a misfire sending raw fuel ito the exhaust system (which would have shown up in the smog results as high hydrocarbons) or a rich fuel mixture (which would have caused high CO numbers). Both would have caused the catalytic converter to turn blue from excessive heat but it didn’t and my numbers all looked good. 

    A third but less likely cat killer would be a lean fuel mixture which would also cause high combustion temperatures. One way to test for this is to hook a volt meter to your oxygen sensor that you can read while driving. The output voltage will tell you your air fuel mixture. I’m not going to do this yet because I have another thoery. The engine was just rebuilt. Maybe a condition existed in the 18 months between installing the cat and rebuilding the engine that caused it’s death. Something that was subsequently fixed during the rebuild. 

     I’m working with Magniflow and my smog shop to figure it out and will keep you posted. 

Until next time rustlovers,

Don’t kill the cat.