496 Workhorse Vortec running rich

I hope this is the correct forum for a gas Class A, if not mods please move it.

I recently purchased a 2005 31' Tiffin Allegro with the 496 Workhorse Vortec motor with a Banks header exhaust system installed. It was running rich at the time, I replaced the plugs, wires and heat shields.

It still idles rich and is diesel like rich under load. I cannot see any O2 sensors in the system and hear rumors about a Mass Air Sensor that may be the issue. I don 't know where it is located, the part no., etc.

There are no codes being thrown and no check engine light.

Until I can locate a repair manual for this motor, can anybody pass along any ideas?

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C Nash

Senior Member
i guess my first thought is ,how do you know it's running rich? Is the computer system working? If so, it should be setting a rich code. MAF should also set a code if system is working. Welcome to the forum and keep us posted
It's obvious by the amount of black exhaust, as if it was a diesel pulling a mountain pass! I've been told the W22 Workhorse system is notorious for not throwing O2 codes, particularly the early models, this is an '05.

C Nash

Senior Member
Most I have had experience with have been notorious for having codes LOL I am thinking someone has disabled something when adding the Banks system. I would get it hooked to a reader and see if the computer system is working. If it is throwing that much black smoke there is no way the check engine light should not be coming on. be a simple check for any qualified tech to check to see if system is working. If the banks system was installed proper there will be o2 sensors installed in the exhaust. Sure duels have been installed. Will the check engine light come on with just ignition turned on and not running? You could be in for some expense to straighten this out if you cannot do or have a friend that is familiar with computer systems. Good luck and keep us posted
I installed new O2 sensors Friday morning before leaving town on the fishing weekend.

I was (pleasantly) amazed how nice it ran, none of the smoke at idle or soot spitting out of the exhaust. Running down the road was sweet, much more power, no lag or bucking and no billowing black smoke on hills.

A shame I made two changes/repairs at the same time without testing each effect so I don't know which made the biggest impact. I will say the MAF appeared to be clean from the start, but I sprayed the heck out of it anyway.

Thanks for all who passed help along the way, I appreciate all of you.

C Nash

Senior Member
thanks for the update Alaskaman. Amazing how some will never report back. Still just don't understand why no code was set. Hope the fishing was great. Are you in Alaska. have a daughter there.
Hi Chelse, yes I'm in Alaska, where is your daughter in Alaska? We lived in South Anchorage for almost 40 years, pulled out in 2010 to travel for a few years, couple years North of Austin Texas, couple in Tri Cities, Washington and two years in Nine Mile Falls, Washington with stops in between, then the magnetic force of grand kids sucked us back up here, we're in Meadow Lakes, just outside Wasilla. Came up in August of last year for our grand daughters wedding, bought a new log home that was under construction, completed in October so here we are.

Fishing was relaxing although the hike upstream through shoulder high grass and over growth in heavily populated bear territory was a little nerve wracking with his wife and two young boys, my son and I were both packing heat, didn't see any sign fortunately while out Friday and Saturday. Lots of Pinks and Humpys we cut loose and my son caught a nice Silver, about 24".

C Nash

Senior Member
Daughter is in Healy Alaska, Alaskaman. She will be coming here the 20th for my knee operation. We made the trip in our MH to Alaska in 04 and it was awesome. Wish we could come back. Would love to fish there. We were out exploring walking through some high ferns and I made the remark that "it's sure nice not to worry about snakes" Then it dawned on us "Yes there are bear here LOL"