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

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

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.

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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

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.

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.

Thanks Mike for the tip.

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

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?

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.

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.

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.