I have a 180 degree fan switch in my car and I think a 160 degree thermostat (I didn't install it). My car would not get through emissions on HC. I know the car never gets above 170 degrees and I'm wondering if that would cause high HC readings and an emissions failure.

If so, would a 190 degree thermostat take care of that, even with the 180 degree fan switch?

 

thirdgens were designed to run HOT... this heat burns up extra emission crap, and stuff... try changing to a 195 stock thermostat and see if that helps, then switch back after the emissions test...

 

that certainly could cause a problem. i wouldn't worry about the thermostat since it probably won't be a problem in testing. the temperature will get hot enough as long as you use the stock fan settings.

 

yea they were designed to run hot.... when i had the 305 in here with stock thermostat it's operating temps were in between 195-220.

 

The low temp can cause an emmission failure for HC. HC is raw, unburned fuel. The cooler an engine runs, the higher the HC and CO readings will be. As engine and combustion temperatures increase, the lower the HC and CO count will be, but at the expense of NOx. The low temp T'stat also may be allowing the engine to go into closed loop operation...if this is the case, the ECM will ignore O2 sensor readings, making it harder to control emmissions. I would change the T'stat either back to stock or maybe try a 180* 'stat. How badly did it fail for HC's?


Darrell

 

I'm not really sure how badly it failed since the tech took it to the emissions station and I have not seen the test results. He said that it passed the test run, and then the HC levels spiked during the actual inspection. Maybe I'll run by the shop tomorrow before work and discuss it with the guy.

Another thing, I had the timing advanced 10 degrees to fight off a running rich condition. He may not have set the timing back to 0 degrees.

 

The advanced timing will not cause a high HC reading...advancing the timing will actually ignite the fuel earlier and cause a lower HC reading. If you have been having a rich condition, this is most likely the root of your problem, and advancing the timing just covered up the problem instead of fixing it. In order to correctly fix the prob (and get your engine back to top efficiency) you will need to find out why it was running rich, correct that prob, then set the timing back to spec.

Hope this helps,
Darrell

 

Thanks, Darrell. We ended up replacing the EGR solenoid and that took care of the running rich problem. It was tested again, but this time it was put on the machine immediately after an extended drive. It was warm enough to pass emissions with flying colors. She's running like a scalded dog and it sure is nice to have the old girl back!

 

Before going into the emissions station change the oil and all the filters..and have that bad boy nice and HOT.