Emissions advice for a Volvo 1988 740 GLE Non-Turbo!!

I have a 1988 Volvo 740 GLE. I am up for emission soon.
The car mpg is very poor in city dirving something like 15-17MPG in
city driving or sometimes worse. But on the highway, it does 20-23MPG.

I replaced O2 Sensor, Fuel pressure regulator, Cleaned the throttle
body, changed Air filter, Flame Trap, Distributor rotor and cap. I
have changed the car's AMM [from the JunkYard], the engine temperature
sensor which sets on the engine block [again junkyard part], the
ignition coil, the ignition wires, and the Fuel filter but all of this
never did me any good. It seems to be just staying at this MPG. I
think I have listed here all the parts that I have changed.

I checked at fueleconomy.gov and found the EPA estimated MPG for my
car and it was 20 City and 25 or 26 Highway. Definitely, I am way
under the estimated city numbers.

Also, my service light gets on when I start the car and stay on for 60
seconds or so and then goes off. Since I owned the car, I was never
able to reset that light. Does anybody know for this particular car
year and model how to reset the service light. Also, does this
specific car have a check engine light or not?

I think I won't be able to do the test unless this light is off. They
won't test the car, right?
Does anyone have any idea or suggestion for me before going to
emissions?

I will probably change the spark plugs and definitely the oil. I will
also try to use some Fuel system cleaner in the gas tank. I was once
advised to use the Ultra i.e 93 Unleaded fuel not regular 87 when
going to emissions. Does that really matter.

I am in Maryland.


Thanks very much for reading the post and for giving me any
suggestions.

--Hameed.

 

I think you have the situation well in hand. The oil change is a good idea
(dirty oil is reputed to increase HC readings). The gasoline shouldn't
matter, but use gas with ethanol if you have a choice. You can also check
the flame trap and the oil/air separator (where the ventilation hose from
the flame trap connects to the crankcase) for restriction.

The emission testers shouldn't care about the "service" light. Others here
can tell you the low-down on resetting that. You don't have an ODBII system
(that started in 1996, although some cars had compatible systems as early as
1994) so there may not be a "check engine" light. My '85 doesn't have one.

The only times my '85 has failed emissions were because of failing to hold
pressure when they removed the gas cap and tested the tank. Both times it
was because hoses were cracked where they attached to the tank. Those were
accessible through a plate in the back of the station wagon (in the trunk if
you have a sedan).

Mike

 

My 1988 240 red block engine wouln't pass NOX despite doing all that
you've mentioned, I finally got it down by plugging the vacuum line as
described below......

If the vacuum hose to the vacuum transducer on the side of the
ignition
control unit is plugged the unit is forced to go to a conventional
advance curve. The NOx will be greatly reduced.

On a similar note--exhaust emissions are modified in two ways via
catalytic conversion. The first stage of conversion is the oxidation
stage where HC and CO are oxidized to form CO2 and water. The second
stage or reduction stage is designed to pull O off the NOx radicals to
form N2 and O2. Volvo has done this for years with a three way
catalyst
built on a single monolithic honeycomb substrate inside the converter
housing. By its design in 1978, the reduction of NOx is less than
efficient, however it more than met the standards of the time that
were
primarily concerned with CO and HC emission reduction. As time passed
the NOx component got more and more regulation attention and the
standards tightened pushing the design to its limits. By the end of
the
red motor run as much tinkering with the rare earth metals plated to
the
substrate had reached its absolute limit. Consequently the later you
get
in the production run the more likely you will encounter NOx emissions
failures during testing. The best strategy is to make sure the oil in
the motor is fresh and the converter is good and hot (run for 30
minutes
or more in mixed traffic conditions) before any emissions test is run.

Bob
--
The goal when driving is to miss the maximum number of objects.



Reply »


ed

Well then, just put something solid in the vacuum hose going to the
vacuum capsule to stop it up, reconnect it so that it looks correct
and
retest. We don't use the I/M 240 test here, but the two speed dyno
test
for preOBDII cars like yours generate %CO, HC ppm and NOx ppm.
Typically
on a 240 in good operating condition you would see CO% ~0.1%, HC
20-30
ppm and NOx arouund 1200ppm. After changing the advance curve by
plugging the vacuum tube thereby restricting ignition advance to
about
33*BTDC max, the NOx falls to 400-600ppm depending on the condition
of
the converter. The fail spec for NOx differs for each year here but
hovers right around the 1100-1400ppm range. I would assume that your
results should a similar percentage reduction in gms/mile.

The only way to reduce NOx formation is to cool the combustion
temperature. The two methods most commonly used are to reintroduce
exhaust gas (EGR) or to retard the ignition timing. With the Chrysler/
MPG
system, as the car starts to move, first retards the timing to 5*BTDC
and then rapidly advances the timing to a maximum of 52*BTDC and
retards
the timing across the board in 19* steps per engine revolution once
the
knock sensor "hears" a ping. Once the ping stops it advances the
timing
again in 2* increments per revolution until it reoccurs, then repeats
the process. Consequently the ignition advance and combustion
temperature remain artificially high, the motor wrings out marginal
extra HP from the gasoline and just pukes NOx. If you were to side by
side test a 1982 with Bosch ignition (standard advance curve) with
your
car the '82 with higher compression and much less efficient fuel
injection, would have slightly higher CO and HC numbers but even with
essentially the same converter as yours had originally would produce
passing NOx numbers.

Bob

If the plug leaks then it works like the delay valve that was
initially
put in the line. If the engine rattled then you had either poor fuel
delivery from the injectors or the engine was running at too high a
temperature while the knock sensor was not sending the proper signal
to
the fuel control unit. Plugging the advance signal hose does nothing
more than force the control unit to behave as it were a later EZK
system minus the fancy individual cylinder retard control.

 

Note that 740s don't have that ignition system, nor that problem.

A 1988 740 would not have a check engine light (they started on 1989 on
non turbos 4 cylinder, and 1990 on turbos)

The service light is just a reminder to do oil changes, and on the 1988
is reset by pulling a lever on the back of the speedo head, similar to
resetting the trip mileage.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

So, I have to take the speedo console all out i.e. unscrew it as if I
am change some of its lamps to reset that light.

Do you know if I get the car to a dealer to read its computer would
that help in determining if there is any emission's problems. Can
these problems be indicated by that service light?

 

You can do it by reaching up from below, but I'd recommend pulling the
cluster out the first time.

No, there's no built in diagnostics at all on your car.
--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Thanks Mike for the tip.

I got some hints about the Air Mass meter from allexperts.com:

http://www.allexperts.com/user.cgi?m=6&catID=802&qID=4617109

"If your AMM has 016 as the last three numbers in the Bosch numbers
then you have a system that uses the check engine light and stores
fault codes. Also most times if you turn on the key to light all the
dash lights it should show up."

I did changed the AMM but it seems I really inseted the wrong part. I
have a 016 AMM where I should have had another version. Might that be
the cause why I am having poor MPG in city driving? My last
measurement was around 24 MPG for pure highway driving.

One last question, what is the best Spark Plugs to use with this
Volvo?
Would NGK plugs be a recommended like Japanese cars?

 

Thanks Mike for the tip.

Another couple of questions:

I heard that there is an AirBox thermostat that controls the
temperature of the Air that gets to the AMM. But I don't find it in my
AirBox anywhere. At the JunkYard though, I did see it in some cars. Is
my car missing it and that is what is scrowing it up or the car
doesn't come with it?

I found people talking about cleaning the fuel injectors at a shop/
dealer would help. Do you think this might help?

Also, some other talked about something called Cold Start valve. Where
is that exactly and how can I know if it is faulty?

--Hameed.

 

Your air mass meter should have 007 as the last 3 digits. This looks
identical to the ...016 air mass except there's an adjustment screw for
the idle mixture beside the electrical connector. There are rebuilds
that replace the cover with the number on it, so what's on an air mass
meter may be something else entirely.

In the air box should be 2 air intakes, and a flap that covers one or
the other. The flap should cover the intake that connects to the hot
air tube that goes to the intake manifold at ambient temps above 15
Celsius.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Your air mass meter should have 007 as the last 3 digits. This looks

I have a 016 AMM. I got from the junkyard. Should I try to adjust the
the mixture using the adjustment screw.

What is the best Spark Plugs for this Car year and model?


Thanks again very much Mike.


--Hameed.

 

There's no adjustment screw on the 016, it's the wrong one for your
car.

I always used Bosch WR7DC (copper) on all those engines.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

There's no adjustment screw on the 016, it's the wrong one for your

Okay, then I am shopping for another one, I guess.
I hope this adjusts the car's MPG.


Thanks a million again Mike. I really really appreciate it.


--Hameed.