Hello, im new here but not to trucks in general. You might have seen me around on GMfullsize.com

Anyways, I have a 2001 silverado with a 5.3 I have done extensive work on. After my last suspension overhaul I needed to make some exhaust modifications. Here is the deal.

-Installed ASM headers
-due to room issues I had to Y the exhaust right after the headers and then run 1 cat. The front 02 sensors are plugged into the ASM bungs and im running sims in the rear.

Now it was runnign bad, I assumed rich and was giving me a IAT error. I found out the MAFS plug was bad and I fixed it, and am now getting a correct IAT reading, it was -38 before. Thing is its still running bad. Its not throwing a DTC. Its backfiring like before and now misfiring (SES light blinks every few minutes). Could this be from running rich and screwing up my plugs? I have autotap but dont know what half of the stuff means, so I can log it and post #s if needed. ANY help woudl be greatly apreciated because I dont know where to start.

BTW I also have a nelson tune if that makes a difference.

Last question, should teh fuel trim be teh same on both banks?

 

What kind of cat are you running? I would think that would be very restrictive but that doesn't usually make you run rich.

Not sure about the other codes but curious about the cat.

 

If it was running bad rich, change your plugs, if it was bad for very long you might have to change your wires as well.

THe fuel trims, long terms should be all that you're concerned with, should be close to the same, not something like -2 on one side and 25 on the other though. If so, that might be an exhaust leak that needs to be fixed.

 

That could mean bad o2's as well. The front ones are all you need to worry with.

Yea, about those cats, errrr, cat, you should have just left it off all together.

 

one stock cat into a dynomax bullet. I didnt want to loose so much backpressure that I lost low end, its an offroad truck and lowend is all I care about pretty much.

Ill pull the plugs and see if they are dirty.

What should my 02 readings look like to see if they are good/bad?

 

They should bounce back and forth between a low reading (.200 or soo) and a high reading (.800 or better). The faster the engine speed, the faster the switching.

Full throttle has a whole different set of rules though, they should be high and stay high, like around .890.

 

ok just monitered with autotap and im getting ALOT of misfires, especially on cylinder 1, 7 and 8. Excuse my ignorance but how are the cylinders numbers on an engine is it

1 5
2 6
3 7
4 8

 

I would change the plugs out. Get some NGK tr55's.

 

Well in conclusion, I replaced the lugs and wires, ran some injector cleaner through and WOW. Its definatly got its power back. I just did my suspension swap (solid front axle conversion) with 5.13s and 42" tires, and I can roast them at will now!

 

Glad to here the plugs and wires worked for ya.

What injector cleaner did you use? The best I've used yet, is SeaFoam, it comes in a white metal bottle. O'Rielly's and Advanced have it that I know of.