1990 Dodge Spirit 3.0 V-6 Emission Test Failure

I am having difficulty passing my state mandated emission test on a 1990
Dodge Spirit with a 3.0 V-6 engine. I recently acquired this vehicle which
has only 32K original miles on it. It was brought in from out of state
where it had not been required to be tested for emissions.

The vehicle has obviously not been driven much but I have driven it for over
500 miles so the gasoline in it was fresh. The station that performed the
emission testing suggested a tune up which I am in the process of doing
before I bring it back for a re-test. About all that can be replaced during
a tune up is plugs, dist. cap, rotor and plug wires. I am also running
gum-out fuel injector cleaner through it and then a product from CRC which
guarantees that you will pass the emission test or they'll refund double
what you paid for it.

I can't help but wonder if there isn't something else that I should to
correct this problem once and for all since it will have to re-tested
annually and with such low mileage I might have this vehicle for several
years.

Any suggestions would be appreciated.

 

What didn't pass? HC? NOx?

In addition to what you mention above, I'd change the air filter and
check the EGR valve. Could be the catalytic convertor is dead also.
Knowing what failed will help isolate the problem. Different pollution
control devices serve different functions. For example, EGR helps to
knock off the high temperature spikes during combustion which reduces
formation of oxides of nitrogen. High HC could be fuel injector
problems, clogged air filter, faulty mass air flow sensor, water temp
sensor, etc.

There's lots of other things to check, but the more information as to
what the failure mode was, the less random parts replacement you will
have to do.

Have you checked for fault codes? I'm not sure about the 3.0 engine,
but my Acclaim with the 2.5L could be checked by cycling the ignition
key as follows: on-off-on-off-on within something like a 5 second window
and then counting the flashes on the check engine light. A long pause
is a separator between digits and a short pause is a separator between
pulses in a digit count. If memory serves, you should start with 12 and
end with 55 and any real fault codes will be in between.


Matt

 

Matt --

Thanks for your input and help. I've enclosed some additional information
below.

Tom

It failed on both. The CO% was 9.44 and the limit is 1.20 -- the HC ppm
was 638 and the limit is 220. Both or these readings were at an idle.

It also failed both at 2,500 rpm test with readings of 8.59% and 281 ppm
respectively. These are somewhat better but still not very close.

The air filter was brand new. I'll have to check the EGR -- that's a good
idea. I guess it could be catalytic converter. I am trying to run cleaner
through the injectors -- it runs so smooth and well it's tough to imagine
them being clogged.

One thing I have noticed about the vehicle is that the water temperature
gauge never goes up very far -- it barely evers goes into the low end of the
operating range -- this is much lower than a previous Spirit I owned and the
Jeep that I have now. Maybe the thermostat is too low or not closing
tightly to allow the temperature to rise. You wouldn't happen to know what
temperature this should be would you ? Probably either 180 or 195 would be
my guess.

I used to own an 1989 Spirit with a 2.5L turbo. I remember the trick with
the codes. I'll have to give that a try -- I had forgot about this "trick"

 

OK, CO isn't the same as NOx. I forgot to mention CO in my first post.
NOx shouldn't fail at idle anyway.

I'll add the oxygen sensor to the list of items above. Basically, it
sounds like you are running too rich given the high HC level. Any
sensor that provides mixture control input to the ECM is suspect.

Could be a thermostat problem. Cool running could cause the problem you
are seeing. I had the water temperature sensor fail on my Chevy truck a
couple of years ago. The engine still warmed up fine, but the computer
thought it was still cold. It ran it very rich which did wonders for
power output, but gas mileage dropped by 40% and the exhaust pipe was
black as could be. How does your tail pipe look?


Matt

 

Matt --

Thanks again for your help.

The codes I got from rotating the key three times were 12 - 51 - 55. Code
51 is related to the oxygen sensor. I don't believe the other codes pertain
to a problem.

See additional information below.

Tom

NOx was not on the print out they gave me -- just CO and HC

Since I got the error code 51 I think the oxgen sensor is one of the the
first things that I'll replace.

The thermostat is a cheap precaution and it's easy to get to so I plan on
changing it for sure. I have no unusual black deposits on the exhaust pipe.

 

Replacing sensors and other parts willy-nilly isn't the way to fix the
problem. Proper diagnosis (starting with a readout of the fault codes) is.

Except in cases of *extremely* rich running, tailpipe appearance is not a
reliable indicator of combustion conditions in any car burning unleaded
gasoline, with or without a catalytic converter.

DS

 

I agree and said much the same thing earlier in the thread if you'd
bothered to read it.

Well, when my water temp sensor failed on my pickup, it was running
extremely rich. I went from 17 MPG to 12 MPG.

Matt

 

Usually, a stuck open thermostat will cause a "17" to be set.

-Kirk Matheson