I really hope that the muffler shop is your last stop on this journey. I love these trucks when they are running and hate them when they are not.

 

Install your new MAF and save your used/cleaned one as a spare.

 

Good news! Keep us informed of how you replace the cats without going factory ($$$$). I'll clean my MAF this weekend!

 

Me too and it is really frustrating.

But there is a bright side. At least I have some idea how to fix things. Since my closest dealership is 1.5 hours away it is sort of a necessity.

I'm about to go to the muffler shop and hopefully that will be the last step.

 

Last night I just dropped the exhaust and ran it a bit. Very loud but no misfires and no retarded throttle response. There is absolutely no danger that I will get factory cats. I'll let you know.

 

Absolutely. I am still astonished that a tiny little wire on a piece of plastic can make such a difference.

I did replace the security screws in the MAF with some plain old bolt head screws that don't require a special tool.

 

The muffler shop was closed. So I got a welder and some pipe instead. I am now confident that my catalytic converters were causing left bank misfires.

I am equally sure that a Disco II sounds like a glass bottle rolling down a hill without cats. Don't ask me how I know. Which brings me to my next question: has anyone put aftermarket cats on your Disco II 4.0 and has a recommendation for brand/model?

My sole remaining problem with the engine is that my front o2s are not being recognized. The data stream shows them at 0 volts and keeps the fuel system open. As that's not directly related to this thread, I'll work on it and post any questions elsewhere.

So, the summary here is that my misfires began with a blown head gasket. Fixing the HG, I was careless with my wiring harness, which unleashed a world of problems. The antifreeze and gasoline that ended up in my exhaust pipes clogged my catalytic converters. Mass air flow sensors are made of butterfly wings so cleaning them doesn't work (my cleaning success was very short lived; it has now been replaced thanks to my buddy).

This was a very expensive distraction from the enjoyment of my truck. BUT I learned a lot. I'm very appreciative for the help and encouragement I have received here. I'll look for opportunities to offer the same to other forum members.

Best,

Charlie V

 

As a postscript I ordered new front o2s and they work. They show voltage and the fuel system closed. I now have no codes, no misfires, and no idea how o2 sensors can go bad in two weeks (like the previous set).

Thanks again to everyone who helped, and to DiscoMike and Antichrist who also helped via PM. Yet again, this forum helped me solved problems that of not solved would have resulted in me abandoning the DII.

Best

Charlie V

 

Great news Charlie. Time to go fishing when it warms up

 

Charlie,

I think we need to put you up for the "Rudy" award. talk about not giving up...

For your cats: http://www.summitracing.com/parts/cto-6904/overview/

Or the magnaflow ones are good too: http://www.summitracing.com/parts/mpe-53006/overview/

For the welding part, make sure you clean the old exhaust really well for the weld joints, especially if using a 110V mig machine. Those are great "homeowner rigs", but if you don't want the heat/vibration sending your cats off into the ditch, prep those welds like you're gonna eat off 'em. Also, for those bends, I usually get a cheap piece or two of extender/universal exhaust pipe from the auto parts store and take the porta-band to it for the small pieces you'll inevitably need for angles in pipe.

Welding help: Welding Tips and Tricks - TIG, MIG, Stick and a pantload of other info

And yes, well done on all of it.

Best of luck!

- dc