Integra Emissions Failure

My 1990 acura integra did not pass Virginia emissions due to high CO2 at 25
MPH. I think limit was 80 PPM and it tested at 140 PPM. It has news plugs,
clean filters, and 173,000 miles.

Is this a simple mixture adjustment? Thanks,

Dan

 

Dan,

Please post the full test results..

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Barry:

Thanks for the reply. Here are the full results:

15 mph
25mph
LIMIT READING RESULT LIMIT READING RESULT
HC ppm 137 37 pass 130 99 pass

CO% 0.76 0.05 pass 0.80 1.45 FAIL
NO ppm 1052 699 pass 0957 689 pass
RPM 3490 bypass RPM 1878 bypass
DILUTION 14.35 valid DILUTION 15.05 valid


Visual Smoke and all Emissions Control Inspections: pass


Dan

 

recent oil change? drive at highway speeds for about a half hour to get
the engine nice and hot? O2 sensor (s?) ever been changed?

according to what i posted before, it *looks* like your O2 sensor/s
is/are marginal.


was it CO? or CO2?

id probably take it to a mechanic, see what they say, and then do that.
isnt there anything on the web that generally will tell what a
particular high reading is indicative of?

sure...

********************************************************************************

What causes high HC (hydrocarbon)? High HC is caused by incomplete
combustion; in other words, the air and fuel that went in to the
combustion chamber was not completely burned, now the unburned fuel has
ended up in the tailpipe. Problems that can cause incomplete combustion
include:

* An ignition misfire. If a spark plug does not spark, the air/fuel
mixture in the combustion chamber does not burn and then goes out the
tailpipe.
* Incorrect air fuel mixture. If there is not enough fuel in the
combustion chamber to ignite, the fuel that is there goes out the tailpipe.
* Low compression. If the compression is too low the air/fuel
mixture will not ignite and the unburned fuel will go out the tailpipe.
* A bad catalytic converter. The converter lives in the exhaust
pipe and burns unburned gas as it passes through.

What causes high CO (carbon monoxide)? High CO is caused by a rich
air/fuel mixture. The air fuel ratio should be 14.7 parts air to to 1
part fuel. Problems that can cause a rich mixture include:

* Problems with the feedback system (the system that regulates the
fuel being added to the engine based on the amount of oxygen in the
exhaust).
* Problems with a computer sensor such as the coolant temperature
sensor, air flow meter, MAP sensor, etc..
* Problems with the fuel pressure. Fuel pressure that is too high
can cause a rich mixture.

What causes high CO2 (carbon dioxide)? High CO2 is the product of a good
running engine. The better your engine runs, the more CO2 it produces.
The only way to reduce CO2 emissions is to buy a fuel efficient car. The
bigger your gas guzzler, the more CO2 it makes. This is what's so sad
about the recent SUV trend. In addition to depleting the worlds oil
reserves, and putting our country in a position where "we will go to war
to protect our oil supply", the trend of building increasingly
inefficient behemoths is making the planet a less hospitable place for
our species (and others) by contributing to global warming.

***************************************************************************

What causes high O2 (oxygen)? High O2 can be caused by a lean air/fuel
mixture, but most of the time, noticeably high O2 is caused by either a
leak in the exhaust pipe allowing air to enter, or air injection pumping
air into the exhaust (this is done on some cars to aid in the burning of
HC). High O2 is not a problem unless the smog machine decides the
exhaust sample is too diluted to use; in which case, the car may fail
the smog test for dilution.

What causes high NOx (nitric oxide)? NOx is not measured in our area
currently, but if your car is registered in an enhanced area (an area
that requires testing of NOx), you may run into this problem. High NOx
is caused by high combustion temperatures and pressures. Problems that
can cause high NOx include:

* An inoperative EGR system. The EGR system was designed
specifically to reduce NOx; that's it's only function. The EGR, which
stands for Exhaust Gas Recirculation, allows exhaust gas to enter the
combustion chamber through the intake. The exhaust gas has a cooling
effect on the combustion chamber.
* Over advanced ignition timing. The more advanced the ignition
timing, the higher the combustion chamber temperatures.
* Overheating. If the engine temperature is too high the NOx
emissions will go up.
* Lean air/fuel mixture. If the air/fuel mixture is too lean the
combustion temperature will go up.
* Compression over specification. Normally when we think of engines
aging we think of the compression going down. However, there are a
couple of ways the compression can increase as the engine is used. One
is carbon buildup on the tops of the pistons. When carbon forms on the
tops of the pistons, the combustion chamber area decreases and the
compression ratio increases. The carbon can be manually scraped off the
tops of the piston to correct this problem, but that would require
disassembling the engine. Click here for cheap alternatives.
* Mysterious reasons. Sometimes NOx is too high and there's no
obvious cause: the EGR works, the timing and advance work normally, the
engine temperature is within range, the air fuel mixture is good, and
the compression is within spec.. When this happens you can try a little
tweaking. If there are two thermostats listed for the car, use the
cooler one. If there are two spark plugs listed for the car, use the
cooler one. Retard the timing 2 degrees (the maximum allowed). Clear out
the EGR passage even if the passage seems fine. Cross your fingers.

 

Oil Change? How does that play?

A couple of weeks ago, on a dark and stormy night, I chose to drive over a
rock instead of swerve around it. My Honda Civic isn't as high off the
ground as I thought. I cracked my aluminum oil pan.
As I pulled over to check for damage, my Engine light came on, which the
manual says is associated with emissions controls. The oil pressure light
never came on, and there isn't any oil level sensor.

$814 later, the car seems to be fine. $262 for the oil pan, seven hours
labor.

 

++++++++++++++++++++++++

A PCV stuck open or shut will screw up lots of stuff. Have you ever
changed the PCV? It's probably a DIY job.

'Curly'

 

most engines will burn *some* oil, however miniscule, either through
blowby, or the PCV system. its best to make sure the oil that is burned
is new, containing as little diluted gas and crap as possible.

theres a bit of "voodoo" factor in there as well.

 

Based on the #s provided, I suspect there is some sort of fuel control
problem.. HCs are elevated at 25, but fine at 15. CO is fine at 15
MPH, but off the chart at 25 MPH.. So somewhere along the test, I
think the car broke into open loop mode. (non-fuel-control) This is
something you may want to send to a mechanic.

I once had an 87 Dodge Colt? pop in and out of fuel control, dash temp
gauge suggested it was at operating temp. The connector to the
separate ECT (coolant) sensor was making an intermittent connection
and bouncing the car in and out of fuel control.. Fixed the
connection and the car passed with flying colors.

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i second that. had an identical problem with a civic - fixed the leaky
radiator and the sensor stopped getting airlocked & sending the wrong
signal to the ecu. it was fine after that. beware the expension bottle
- it can look normal but the rad can be empty.

 

A faulty ECT would go into open loop mode on all rpm range. It
appears the OP pass the low speed test that indicates the ECT is
good. At higher cruising speeds the ECU will rely mostly on the
O2 sensors' response. If the close loop responses are bad it will
show up on the 25-mph readings.

 

This should be covered under your collision insurance if you want to
file a claim.

 

Initially, I thought the cost was going to be a little lower ;-) and I
wasn't planning on filing an insurance claim.
I did file an insurance claim, and received the payment within a couple of
days.

 

However, an intermittent ECT circuit can go in and out of closed loop
at all speed ranges. I've personally seen it.. I respectfully
disagree with your analysis. The car must be at operating temperature
before the test begins. Based on the 15 MPH readings, the fuel
control system is operating correctly. But at 25 MPH, it is not.
This suggests to me that at the beginning of the test, the ECT was
functioning correctly.

If the closed loop data were bad, you would see it at both 15 and 25
MPH tests. That was not the case here.

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I was taught a while back that if the ECT voltage goes cold on a
Honda operating in closed loop the fuel will be unaffected, but the
idle will increase.