Hi all….I just got my truck smogged and it passed just fine. All the numbers look good (CO and Nox) but the HC numbers are about 2/3 of the allowable max. Well within range but I would like to see what I can do to lower this particulate.
I’m familiar with the basic ways to reduce the numbers such as replacing cats, egrs, PCV valve, tune-up, etc. but I would like your input on specifically reducing HC. Your thoughts?

Here is the vehicle and what I have done:
94 Toyota Pickup
22re 4 cylinder & 5 speed
440K miles (engine all original/ head never off)
No oil burning at all
New cat
New egr valve
New 02 sensors
New distributor
New spark plug wires
New TPS
Fresh tune up
Seafoamed regularly

One important thing I wanted to mention is the timing chain. Mine is original (440K) and yes, I’m overdue to replace it. Can I have enough chain slack to the point where it A) affects the valve timing and B) is possibly affecting the HC numbers?
Thanks, Kit

Hey dude,

I don't know how to lower your hydrocarbons.

If you want to lower your carbohydrates, there's zillions of articles about that online.



Have you checked with any of the GGF "brain trust"? Marty W, Brian G, John S aka fierobear . . . but even before that, how about posting this in the Pennock's Other Cars section?
https://www.fiero.nl/cgi-bi...number=10&LastLogin=

I can point you to a couple of auto service and repairs in Mountain View that I have patronized for many years. PM me if you'd like that.

[This message has been edited by rinselberg (edited 01-13-2022).]

E-85 is one way to beat the sniffer

quote Originally posted by Kitskaboodle: Hi all….I just got my truck smogged and it passed just fine. All the numbers look good (CO and Nox) but the HC numbers are about 2/3 of the allowable max. Well within range but I would like to see what I can do to lower this particulate. I’m familiar with the basic ways to reduce the numbers such as replacing cats, egrs, PCV valve, tune-up, etc. but I would like your input on specifically reducing HC. Your thoughts? Here is the vehicle and what I have done: 94 Toyota Pickup 22re 4 cylinder & 5 speed 440K miles (engine all original/ head never off) No oil burning at all New cat New egr valve New 02 sensors New distributor New spark plug wires New TPS Fresh tune up Seafoamed regularly One important thing I wanted to mention is the timing chain. Mine is original (440K) and yes, I’m overdue to replace it. Can I have enough chain slack to the point where it A) affects the valve timing and B) is possibly affecting the HC numbers? Thanks, Kit

It's been a REALLY long time since we've had emissions and safety testing in Florida... we abolished both in 1999 if I remember correctly.

What I do remember though is that hydrocarbons were more prevalent when the car ran cool.

If your car runs cool... and the engine is cool, it's likely not burning them off as much. You can run your car hotter (replace the thermostat with a 195). Chances are, you did what any good car guy did and replace your 195 with a 180. If that's the case, make sure you put the 195 back. Also... retarding the timing can also fix that (if it's within your control... don't know if you have a distributor). A "slightly" retarded timing will delay ignition and allow your car to run longer in compression before firing.

Hope that helps...

82 TA, I believe you are on to something.
My truck does indeed run very cool. Years ago, I was having thermostat sticking issues and as you mentioned, many people go to a lower temp thermostat. That was my reasoning also. I also reasoned that small, 4 cylinder aluminum head engines (being more susceptible to overheating and head warpage) could benefit from a lower temp thermostat. Lastly, I thought that as long as you got the cat hot before the smog test, you were going to get good numbers.
All that being said, I just might try what you said and switch to the factory thermostat just before my smog test.
Thanks for all the replies!
Kit