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Shouldn"t I pass Smog if Renix gets 20mpg?

my2monkeys

my2monkeys

NAXJA Member
Location
Mission Viejo, CA
My 89 4.0 is up for CA smog in Feb.

Passed well 2 years ago.

Have been getting a steady 19-20mpg mostly highway 70+mph.

Question is: Does Good fuel consumption indicate an efficiently running mill?

Also does anyone know how to check the HEO2 signal, not just the heater element curcuit?:wow:

thanks fellas
 
There are more things in a CA smog test than emissions. Given that your mileage is good, chances are your O2 sensor, as well as the other sensors, are working OK.

You can typically test the O2 sensor by backprobing the signal supply. Once the engine is fully warmed and in closed loop, you should see the voltage fluctuate above and below .45v.

Just bear in mind that the CA test includes a visual inspection of vac lines, egr function, and pressure testing the evap system (pre OBDII) and gas cap. Any of these can cause you to fail.
 
Thank You for your reply.

I keep it all stock under the hood and new gas cap too.

I know what you mean about that new evap. test, my moms 86 T-bird passed everything but that and it was $ 200.00 to find and replace bad vent hose.

The CA smog is crazy because my Pop's 86 El Camino w/305cu.4bbl carb. runs like dog doo and passes everytime-go figure.
 
Addressing the base question, good mpg and good emissions ought to go hand in hand but don't always. Remember that putting power to the piston at just the right time, etc., is not entirely the same as burning the gas in the cleanest possible way. Hence such things as catalytic converters and EGR. My furnace is very clean and efficient but it takes forever to drive it around the block.
 
Matthew Currie said:
Addressing the base question, good mpg and good emissions ought to go hand in hand but don't always. Remember that putting power to the piston at just the right time, etc., is not entirely the same as burning the gas in the cleanest possible way. Hence such things as catalytic converters and EGR.
My furnace is very clean and efficient but it takes forever to drive it around the block.
Click to expand...
Click to expand...

Now that's funny right there, I don't care who you are:gee::D
 
Now I want to take my furnace on a road trip! it has the same aerodynamics as my jeep:D
 
my2monkeys said:
My 89 4.0 is up for CA smog in Feb.

Passed well 2 years ago.

Have been getting a steady 19-20mpg mostly highway 70+mph.

Question is: Does Good fuel consumption indicate an efficiently running mill?

Also does anyone know how to check the HEO2 signal, not just the heater element curcuit?:wow:

thanks fellas
Click to expand...

See my post #12 in this thread:

http://www.naxja.net/forum/showthread.php?t=911289

A lean engine gets better mileage, but produces higher NOx emissions. What failed in the test? NOx?
 
StealthXJ said:
If you read the OP you'll see that nothing has failed, yet. He hasn't gone in for smog. He was just asking ;)



:)
Fred
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In that case, the best recommendation I have is to run some carb cleaner through the throttle body intake and injector cleaner in the gas and clean out some carbon deposits before the smog tests to knock down the carbon deposits that increase NOx emissions. The guy I use for inspections says he does that for NOx only failed emissions vehicles and it fixes the problem every time if it was just an NOx problem. As said before, if the Cat is toast it can still get 20 mpg and fail HC and NOx limits.
 
four_shot said:
Now I want to take my furnace on a road trip! it has the same aerodynamics as my jeep:D
Click to expand...

We use a coal stove to heat the house. I wonder how many MPT (miles per ton) it would get!

Maybe a can of BG44k would help also. I used it a few months ago, chasing what was either a weepy injector or bad fuel pump check valve. Starts like a champ now, and it even cured a barely-audible mis-fire that was noticable only at idle. Like a tune-up in a can!
 
5-90 lectures that the carbon build up leads red hot carbon spots during combustion that leads to pre-ignition and hot spots that increase combustion temps and raise the NOx formation. The various formulas that go through the injectors and directly into the vacuum lines or throttle body help dissolve and burn the hard carbon deposits. I have actually seen, had the carbon burn through a head gasket between cylinders!!!
 
180740d1295196494-89-4-0-ca-smog-evap-test-fail-100_2945.jpg
:gee:UPDATE; Did the CA smog yesterday and Passed the Tailpipe emission tests but Failed Evaporater Test

So I dropped the tank and sealed up the 2 rollover valves and grommets that were not sealing good.

Also clamped hose from canister to metal hard line under MAP sensor that was suspect.

Hopefully I can do a Pretest for Evap. because CA Smog rules make you take the complete Smog test over even if you passed Emissions already!

Ohwell, just another $80.

All let you know what happens tomorrow.:gee:
 
PASS - Tailpipe Emission Test

PASS - LPFVT (low pressure fuel vapor test)

After fixing vacuum hose leaks and varifying no leaks (by blowing in the fuel tank vent hose at canister and listening for air and pressure being let back out of hose I blew into:eyes:).

Really not that big of a deal cause there is only one vent tube from tank to charcoal can to go bad.

Also got to check fuel tank filler pipe and filler vent pipe for tight hose clamps.



Now I'm ready to add that STP w/ZDDP to see what happens to my top end clatter.(was afraid sulpher might throw off Smog Test)
 
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