How do I know if my car is running rich?

[5speedz34]

Well last week we tested our cars in Science, (thank god Michigan does have emmissions testing), and my car failed horribly I think if I remeber right is was high in the CO and hydrocarbons, and someone told me my car is running rich, how can I tell if it is?

[Juglenaut]

Look at your plugs>>>

[5speedz34]

Look at my plugs for what?

[Juglenaut]

look at yee plugs yight...Tell me what yall look like

[4spdz34]

they will be black and full of carbon tony. normal is a offwhite to a tan color

[Juglenaut]

whoa mine are tanish white on my GP right on.

Iriduim NGK's

[dykz34]

FUCKING SPARK PLUGS! What else?!

[pocket-rocket]

Look at the stock code in the chip, all cars run a little rich so they don't lean out. Carbon is easier to clean then replacing valves and pistons. A little more gas is easier to pay for then a new engine too.

Also, Tony, if you plugs have a bunch of carbon on them, think back to the last time the O2 sensor was changed, if you can't remember, replace it and that should help some.

[Cotton]

if the T-stat is stuck open the engine will not reach normal operating temp, the ecm will feed it fuel.......and it will fail the emissions test.

[Juglenaut]

The only thing the ECM uses engine temp for is to adjust fuel really to avoid vapor lock, and some other things.

So yes it will run a tad richer on a cold engine, but not much...

I noticed even with the T-stat forced (wide open) to stay open my engine never got hotter than 170 on a hot day with both fan going, on a normal stuck open T-stat I got to 195 or abouts with the same conditions.

I always put an adjustible stat in my engine in summer.

We talking a small amout of fuel at a cold 170 versus 195 or more. Climate dependant.

[Cotton]

sorry, eng coolant temps below 170 means "open loop" operation, that means no pass emissions, therefore, its rich enough to fail.

[Juglenaut]

sorry, eng coolant temps below 170 means "open loop"

I think you need to check that again.

[Cotton]

sorry, eng coolant temps below 170 means "open loop"

I think you need to check that again.

i'll do that while you research what "vapor lock" is (or was)

[Juglenaut]

Open/closed loop is the point at which the o2 sensor adjusts stoitch to control emmisions. Open loop switches on WOT/load, power enrichment.

If you are going to refer to open loop then temps on the o2 will be much greater, given that the point where it hits closed loop on a cold start varies some depending on the T-stat. Running a cold engine does increase wear..Running richer on a hot run will induce vaporization into the manifold, as if there is to much gas, the vapor will "lock" agaist incoming air as it will saturate the port thus the oxygen will be displaced. The important factor is the o2 which hits Closed loop at about 6000F, ECT open/closed loop can vary by climate and where the car is going to be driven the most, this is a preset parameter and can very from 140-180 degrees F.

All engines are set to run rich, but any ricer on a hot engine will enduce "lock" common sympoms>>backfires in the exhaust, manifold and/or plenum drawback in which fuel may expand/detonate in the intake/plenum

[Cotton]

"vapor lock" is a situation known only to carburated engines. The heat in the eng, carb, etc causes the fuel to vaporize in the fuel bowl, this slight pressure in the bowl is sometimes strong enough to keep the "needle" on the "seat", effectively sealing the carb inlet just as the float would do in a carb that is operational.
later models used evaporative/purge systems to relieve this vapor pressure, along with bowl vents connected to "charcoal canisters".
when a carburated engine is experiencing "vapor lock", the fuel pump (an average pressure of 6psi), is unable to overcome the vapor pressure in the bowl that is holding the float up. therefore you have "vapor" (the cause) "lock" (the effect).

since "port" fuel injected engine generally run at 35+- psi, the vapor point of the fuel is increased greatly, add in the work that the "fuel pressure regulator" does and you have a near constant circulation of fuel which any vapor created within the fuel sys would be purged in to the tank.
Todays "evap" systems are used for the sole purpose of removing the excess vapors from the fuel tank, and feeding the vapor to the engine to be burned with the rest of the fuel. This reduces capor emissions, and prevents the fuel tank from becoming pressurized. (ever notice a gas can swell up in the sun).

what you are describing may be "reversion", when the incoming fuel/air charge changes direction due to a specific set of circumstances, some of which engineers are still studying.

some programs on some models will allow closed loop operation without reaching the predetermined coolant temp, only after eng has operated for a set amount of time at specific speeds. Most Gm programs (up to about 92) would only allow closed loop after reaching a specific coolant temp. If we are speaking of "throttle body" injected engines, then we have many different situations to keep in mind. As far as i know, all V-6 "W" body cars are "port injected".