ok so i have a 97 ram 2500 4x4 new to me and was running pretty rough when i got it. so i looked up some things on here and got info from friends and started to fix everything first off was new exhaust the cat and muffler were trash and same for the o2s. next was the plenum gasket intake manifold gasket valve cover gaskets(just cause i was there and everything was accesible), exhaust manifold gaskets, cap and rotor, plugs and wires, and iac. once those were done it ran soo much better missfire seemed to be gone smell of unburned fuel was practically gone seemed like i was well on my way to puttin life back into this beast. then i had my exhaust header crack they are aftermarket headers put on by the previous owner and i would like to keep them on. so we tried welding them and what a difference it made better sound and maybe im crazy but seemed to even drive better. our welds lasted for about a week and then they cracked on the weld again. i drove with it like that for about a week probably puttin about 1oo-150 miles on it. it suddnely seemed to get worse louder and the truck seemed so unresposive. is this all from the cracked headers? if it is do i need to replace the headers or is there a proper way to repair them? the truck seems to have no back pressure and almost seems like its delaying when trying to shift into second. all the info you guys can give me would be great thank you in advance

 

They must be cheapo's, I'd replace them and eliminate the headache. As far as the way it run's, no leak is good, but one before the o2 sensor will mess with it, and the pcm won't receive the correct signals, therefore the pcm won't send the correct info to the various other components, like injectors for instance.

 

the heders are mopar performance and from what the exhaust shop and other people have told me they are or were nice. iv considered the thought of maybe i lost an injector or two the last codes i pulled were for random missfire cyl# 14 and i think it was 7 or 8. the leak messin up the o2s makes sense but im not sure it would actually kill power the way it has i dunno i could be wrong. and if there is no way to fix the headers what would be a good place to look for some new ones?

 

Not a lot of choices for headers for our trucks. At least, not for what I consider a 'reasonable' cost..... Do you have shorties? Or long-tubes? Which would you prefer? Still have the stock Y pipe? I see you are in california...... so, your choices become even more limited....

 

they are shorties and they are carb approved and from what i can tell they are still on the stock y pipe and im originally from colorado and most likely will be back there in june so changing them to somethin not ca approved is really no big deal. honestly im not sure what the difference between shorts and longs would be guess i should research. i dunno i think cheap right now is the way to go just cause im in school and have limited funds. also i found that the triangle donut gasket on the collector i guess you would call it blew out again on my truck and i lost a bolt with it. now iv been told today that the cardboard lookin gasket i got from the exhaust shop was crap and i cant use them on my truck? is this right? they said use copper is this right?

 

If you don't have to register your truck in CA, and consequently don't have to go thru their inspections, there are a host of shortie headers available, all of which will bolt to the stock Y pipe. Check Summit Racing, or Jegs, find a set you like, and order 'em up. They should come with all the gaskets and such. Do you have a place to work on it there? Or is this something that is gonna have to wait until you are back home?

Properly installed gaskets are ok..... coppers are better, but, more expensive.

 

i am actually in school at wyotech so pullin some shop time with good tools is definitely possible. and this is definitely somethin i would like to fix sooner than later. i seem to have a missfire that wnt go away and everytime i think i find a possible solution i discover a new problem and try to fix it. the exhaust is kinda tops of the list with the missfire cause i actually have to do emissions out here now. im not sure if the exhaust leaks would have too much to do with the missfire. i dont think the leaks would alter the o2 readings enough to make it dump fuel like it is and create missfires i could be wrong tho.

 

You might very well be wrong, actually, and it's a good thing if you are.

A big leak upstream of the oxygen sensor will in fact cause the problems you're seeing. First exhaust pressure pushes combustion gases out, then the scavenging of the system downstream of the crack pulls atmospheric air in, so you end up with a diluted exhaust stream at the oxygen sensor which will cause misfire detection and a rich mixture.

Misfire detection is an interesting mechanism. The PCM knows when to expect exhaust gas pulses to reach the upstream oxygen sensor, so it knows which cylinder is responsible for each pulse. If it sees too much oxygen during a pulse (or no pulse at all where it expects to see one), it assumes the fuel/air mixture wasn't properly ignited during that cycle and records it as a misfire. So when you have a leak that dilutes the exhaust stream you catch misfire DTC's even if the combustion process in that cycle was absotively posilutely perfect.

And of course diluting the exhaust stream will cause rich mixtures because the PCM averages the readings, sees that extra oxygen, and says to itself, "Hmmm... runnin' lean now, crank up those injector pulse widths to get back to normal".

You might have other problems, but what you're seeing is perfectly consistent with a fat exhaust leak upstream of the oxygen sensor.

 

ok that actually makes alot of sense now so one other question. would the cracked headers cause the collector gaskets to blow? cause iv replaced them twice and each time they have gone out. also i know the after cat 02 is the catalyst efficiency monitor and if that were to be bad would that cause the system to try and compensate any?

 

I guess that depends on why the header cracked in the first place. If it's because they're carrying weight or are being torqued this way or that by a screwy exhaust hanging job rather than just hanging there unencumbered, then yeah, I'd expect that to lead to gasket failure. Headers last longest when they're supported at both ends so they're not even carrying their own weight.

Nope. All that one (effectively) does is indicate to the PCM whether or not it should set a DTC and turn on the CEL. It has no effect at all on engine operation.