A little while ago I had trouble passing smog. (High HC). I replaced a bunch of parts (distributor rebuild, fuel filter, plugs, O2, PCV). The tech said the emission readings smoothed out after he let the car running for a while. The car passed but the HC is still a little high at idle. Also the car doesn't sound
perfectly smooth. I was worried the car wouldn't pass because during the test there were periodic moments when the car started sounding a little rough. Not very rough and fairly brief.
How smooth is the idle supposed to be in a perfectly running engine? Mine moves about +/- 100 rpm. Enough where there is an audible change.

There are no codes and for the last two months the car has been getting a consistent 20 MPG (70% highway 30% street).

Overall the car runs pretty good but I took offense when the Smog tech said hes seem better running 3rd gen Firebirds.

This is my only car and I can't afford for my car to all of the sudden die. Which is also why I am interested in identifying a part that could be on its way out.
My car has 132k miles.

To summarize, how can I get the car to run in tip top shape and which parts tend to wear out/fail at 130k+ ?

Thanks.

 

i've never had to pass an emissions test of any kind (the one thing indiana has going for it lmao), but since you've already replaced your O2 sensor, you should probably try a new cat. if your core is physically busted (like if the car has ever backfired, or ran fairly rich) it will give the car a harsher sound so that's what i'd try. also make sure your car is nice and warmed up before the test.

p.s. tap out your air filter if it's dirty. won't help very much, but if it's filthy it could help just a little tiny bit.!?

p.p.s. ok sorry, if your CO isn't that bad, it's probably not your cat. this might sound silly, but try some Sea Foam. it could do the trick for you...and definately make sure that the car is RLY nice and warmed up, like take the longest route possible to the test station. a properly warmed up car makes quite a (positive) difference in an emissions test from what i hear.

p.p.p.s. i'm an idiot, just saw that you passed the test, lol!

 

this is copied straight from rxp.com:

"When an engine is new it is usually very efficient. This means that when gasoline is injected into the piston chamber more of it is consumed during combustion than in an older engine. However, internal combustion engines are not very efficient, which means the fuel that is not consumed is transformed into carbon monoxide (CO) and hydrocarbons (HC) emissions. In the new engine the key word is "carbon," because the carbon also begins to build up inside the combustion chamber (cylinder walls, the top of the piston, head, and exposed parts of the valves). This process is called "agglomeration," which means forming a mass from particles that retains its individuality. The more carbon that builds up over time the less efficient the engine becomes. As the engine becomes less and less efficient it produces more and more unburned fuel or CO and HC, which speeds up the agglomeration.

The catalytic converter is responsible for burning CO and HC before they leave the exhaust and enter the atmosphere. In addition, in many new model vehicles part of the exhaust is recirculated to give the engine a second chance at burning these harmful deposits. Unfortunately, over time the catalytic converter and other systems in many vehicles loose efficiency and the engine exhausts more and more pollution. "

you also have to understand that your engine is almost 20 yrs old, it's not like newer obd2 cars designed for 0 emissions. there's just not as much emission reducing technology in a 3.1 as there is in a 2008 chevy w/e.

 

I just wonder if there are gains to me made by replacing parts without rebuilding the engine.

There are parts that have never been replaced and I don't know if those parts are "all or nothing" or slow degraded performance.

Take the fuel injectors, timing belt, MAP and TPS Sensors as an example. Does progressive wear lead to degraded performance or do they work 100% until they ultimately fail.

The fuel injectors, fuel pump, fuel pressure regulator, timing belt, IAC Valve, MAP and TPS Sensors and a few other things have never been replaced.

Considering that my car is running o.k., would I be wasting my money by replacing those parts?

 

i've always tried to follow the "if it ain't broke..." rule, but that's just me lol. i could see belts and sensors as preventive maintenance tho...