Cat drive cycle

[troyboy162]

I have the scantool.net one. Its really old but still newer then my truck lol.

[Seanz0rz]

Let me know if you want to borrow mine.

[troyboy162]

800 miles and the cat monitor is still not good but I passhed by getting my evap to be ready. 96-99 is any one monitor. 2000 and up is only evap allowed.

[Seanz0rz]

Yay! Glad it passed and good to know about the monitors.

[troyboy162]

yeah that's crazy that they make any distinction between the years like that, but somehow my old, boiling gas flooded, charcoal canister is working enough to give the ECU whatever it needed to see.

I'm still clueless on the cat monitor. The guy mentioned there are three things going on in there and maybe the cat wasn't working well enough on one of them. If that were the case I'd imagine not passing smog or at least throwing a emissions related code. Of course I still really don't know jack about whats going on, or most importantly what the computer needs to see for that monitor. I will check again in a few months and see if its set.

[Seanz0rz]

Post up your numbers from the report. Those give good indications on what may be wrong.

[troyboy162]

They are out in the truck right now but do cats go bad, not throw codes, and still pass smog?

[Seanz0rz]

Mine was on the edge of death for years. I barely passed smog the two or 3 times before I replaced it. After the new cat I passed with flying colors.

[YotaFun]

I have seen where o2 sensors slowly going out will make things act funny, they aren't out enough to throw an emissions code, but are out enough to cause some monitors not to set.
Usually however you will notice a dramatic change in fuel mileage or vehicle performance, in my truck, my gas mileage sunk, where are that point I might as well have said I was driving a hummer, and besides the injectors going out the truck just was all around super sluggish...

The year difference is weird, I will have to double check, I can't remember it it was 99 or 00 where the front o2 sensor changed to an A/f sensor and the tolerances for emissions tightened up a little bit.

[troyboy162]

hmm interesting info Avi. My truck has been a dog ever since I bought it so I haven't noticed any decline. My O2 sensors are certainly in overtime though. A precat 02 sensor would make a nice birthday present for her.

Driving the truck hard the last few days to work did show me I had a issue. The rare stumble I attributed to maybe a coil became easy to reproduce by using lots of throttle in a high gear up a hill. I checked the plugs and they were very warn. After I replaced them ithe stumble is gone. The rare surging I thought was my toque converter appears to be gone as well. I wonder if that was the problem with my readyness monitor since I bet fuel probably wasn't burning that great.

The plugs looked good when I rolled the truck a few years ago, but they were certainly past due now.