I have a 94 Lt1 with 66k on it, I took it down to smog it the today and it wouldn't pass. The car is Bone stock except for the hypertech programmer.

I did the water pump a little while ago and I couldn't get the low coolant light to go out after checking the coolant everyday for about a week, so I unplugged the light so I could smog it.

If there is air still in my cooling system would that make the car run too rich?
I just was curious after reading this from www.shbox.com

"The PCM gets it's temp readings from a sensor that is in the water pump. If the reading the PCM receives is inaccurate, the fans may not come on at the correct time. The PCM also uses this temperature for lookup in fuel calculation tables. If there is a problem that causes the reading to be always low (cold), the PCM will add extra fuel. This can cause hard starting when warm and an overly rich condition when running."

I used a hypertech programmer to adjust the timing, and have the fans come on earlier, it says it is legal but maybe I should return it stock?

They also told me I need a new gas cap, but I don't think that would make a big difference.

My hydrocarbons at an idle were 3333 and at 2500rpm were 536. The legal limit at idle is 100 and at 2500rpm is 130.
So needless to say they were way too high.

Thanks for any advice.

 

How did the CO and NOx look? If the problem is mainly unburned HC's, its likely that you are leaking raw fuel into the system (leaky injector, leaking fuel pressure regulator), or that one or more cylinders is misfiring and dumping raw fuel. If CO is also high, it would point to a rich A/F mixture.

 

The CO at idle is 4.70 with a max of 1.00, CO at 2500rpm is 2.86 with a max of 1.00

So the CO is very high too, which makes me think its running very rich...

Any thoughts on what would cause that?

 

Rich A/F ratio is typically caused by a "false" lean condition. That can result form misfires and exhaust leaks before the O2 sensors. A faulty coolant temp sensor (the one in the water pump housing could also cause it to run rich, if its indicating a significantly lower than actual coolant temp.

You indicate you used a Hypertech programmer to "adjust the timing". Since you can't adjust the ignition timing with a Hypertech, I'm assuming you ment you adjusted the fan on/off temperatures to have them operate at a lower temperature. If the engine is too cold, the combustion will not be complete. But it wouldn't be likely to produce the massive amount of unburned HC that your emissions test showed.