Title says it all.
I took my truck for its annual test and only for I know the guy working their, there was not a chance in hell that it would have passed the emmisions. There are no codes on it, pulls like a mule, the last tank of gas done 9 mpg (pulling the trailer) and 6 on its own WTF, runs sweet as a swiss watch. It has a new o2 sensor, no cat (X pipe) straight thru ss exhaust from the headers, 180 t stat, performance PCM. I have been reading different threads and came across it that this truck needs the 195 t stat to keep the pcm happy.
Is it possible that the temp sensor for the pcm is not working right but ok enough not to set a code.
Any ideas.
Thanks

 

Is "pulls like mule" a good thing

 

Ya it is. Maybe I should have said it pulls like a freight train.

 

What brand o2 sensor?

If it doesn't like the 180 stat then it will just keep dumping gas into it to try and get it up to operating temp. Not sure if the performance PCM corrects for a 180 stat or anything like that. But stock computers generally don't like 180s, although some people swear it doesn't affect their engine negatively

Does it seem to be running rich

 

I think its Ac Delco, I forget now but it was not a cheap one.
Ya no mistaking its running rich espically when its cold because if you're standing at the at the tail pipe and someone rev's it you can see a bit of black smoke and you know by the smell of the fumes.

 

See if it's Bosch. They don't like Bosch sensors, often cause things to run funky. You just need the first O2 to be good.

I don't think your 180 is helping matters either

 

I just looked up the o2 sensor, its Ac Delco. I will change it back to the 195 stat and see if that helps. On the odd trip it has done 16 + mpg on the 180 but very rarely. More normally it does about 12 -13 on all highway driving and on my normal driving 8-9.

 

Before buying parts that you may not need, plug in to the PCM, and see what IT thinks engine temp is. A failed temp sensor won't always set a code.

 

I plugged in the truck and the pcm is getting a proper temp read out. It started at 46 and rose up to 179 when I went for a drive. The o2 sensor at idle (hot) ranges from .08 to .90 V, It jumps up and down like crazy, is this normal? The scanner read out for the o2 is from rich to lean, seems to be mostly rich.

 

I'm thinking the O2 sensor is being a pain.

Get an NGK or Denso, replace it and see what happens.