You don't need any special tools to check for stored codes. It's pretty simple. Here is a link to a video that shows how to do it. If you get any codes other than 1 - 1 - 1, post them here and someone can tell you what they mean.

http://www.youtube.com/watch?v=odE9LoTQqwg&feature=g-upl


Chances are, if you are not experiencing any drivability problems, your converter is not bad.
However, I would urge you to replace the converter if it is bad. Yes, the car will run fine without one, but they are there for a reason. If you do end up replacing it, make sure that the car is not running rich before it is installed. It would be a shame to ruin the new cat.
--
1966 122s, 1968 142s, 1969 144s, 1979 245dl, 1989 244gl

You are more likely to have a leaky exhaust system than a plugged cat (which would mean less pressure at the tailpipe). If you have no running problems, your catalytic converter is probably flowing fine.

You have a 1991 240.

All internal combustion engines using hydrocarbons for power produce some manner of soot through the exhaust piping. Soot naturally collects on the tailpipe interior. No matter how efficient the engine may be.

Verify Bosch LH-Jet (socket 2 or 6) and Bosch EZK Codes (socket 6 or 2, I forget) using the OBD (on-board diagnostic) 1 diagnostic tool located on the USA driver side inner fender between the driver side hood hinge and the brake vacuum chamber. You have an OEM Volvo green service manual, a Bentley 240 service manual, or a Haynes 240 service manual, yeah?

If the OBD test result in codes other than 1-1-1 through both sockets, post the codes you record here.

Does your 1991 Volvo 240 include EGR (exhaust gas recirculation)? Some did if they were sold in some states like CA. A failing EGR system can futz with emissions. I'll guess you don't have EGR, as my 1991 240 has unfortunately.

Run the codes at least twice and write down the blink number. The 700-900 FAQ may provide some anecdotal information for you as well as the meaning of said value.

Verify the interface between the head-pipe output and the catalytic converter input is solid, does not rattle or seem loose, and is not leaking as shown by soot and black nasty crap collected around the flange and on the heat shield above the catalytic converter. This metal "spin-gasket" (as some call it) flange is a horrible design and some worthless exhaust mechanic may have replaced the prior head pipe or the prior catalytic converter without using new hardware to proper secure the two pieces together.

Also, on MANY Volvo 240s, you may be missing the support at the end of the head pipe as the head pipe on all 240 years, when manufactured, comes connected to any variety of support or brackets that connect to the 3:30-5:30 position bell housing bolts (when viewing the car from the rear forward.

This bracket secures the headpipe and the exhaust system weight from the headpipe where it secures to the exhaust manifold to the first set of rubber hangers supporting the front of the first muffler (or resonator if your prefer).

This bracket also provides a better ground for use by the 02 sensor. In reality, the entire exhaust system should be connected to the body by ground straps terminating in a ground strap between the rear-muffler to tailpipe hardware to the chassis (unibody). Grounding the exhaust system improves 02 sensor performance and reduces (slows) corrosion advancement.

As others state in this thread, eliminate all intake vacuum leaks between the air filter box and where the air intake port meats the cylinder head. Air intake leaks can occur as injector seals and also throughout the entire PCV system (whether or not the PCV flame trap sieve is clogged or not).

I'd start with inspection of the accordion-like plastic intake hose between the AMM (air mass meter), MAF (mass air flow sensor) if your prefer, output. You'll see Volvo lets vacuum and electrical line chafe against this rather frail air intake component. This hose may have chafed on the inner fender.

You can carefully remove this accordion hose, hold it up to bright light and look through it, turning it to see light leaks. An exterior inspection may show holes.

If you find holes in the accordion-like plastic intake hose, you may degrease the exterior of it (or all of it). To seal any holes, I use Goop Automotive, RV, or Marine adhesive type. Apply in several (at least) thin layers over the identified holes. Allow the adhesive to cure (outgas). You may want to tie off the the lines and wires that chafe against this hose. You may want to use a poron or neoprene section with adhesive on one side to protect the accordion-hose from inner fender chafing and chafing against wire and vacuum line and such.

Look at the ends of the vacuum lines connected to the air intake at the throttle body and on the air intake port. Are the hose ends split or brittle? If you have slack, nip the ends off and re-secure. Small hose clamps or plastic zip tie straps can work. Tighten to snug. You may want to inspect the charcoal canister located in front of the USA driver side front wheel under the fender to verify it is secured and that all vacuum lines are secured to it.

When reassembling the large intake piping from the air filter box output to the throttle body, ensure the hose connections are fully seated and that the large hose clamps are properly aligned as you tighten them.

As for your catalytic converter. Verify what the KS-state counties auto emissions requirements are. If you don't have to have your awesome 1991 Volvo 240 tested for emissions, you can probably get away with removing the catalytic converter and running a straight pipe.

If you go the route of destroying the catalytic converter internals (the ceramic honeycomb matter lined with the platinum-palladium-rhodium reagents), your catalytic converter may not last too long. The dual shell design (including thermal performance) is meant to contain the ceramic matter. Also, you won't be able to remove all of the ceramic substrate. You'll always have ceramic chunks blowing rearwards that may clog the first muffler (resonator) and possibly the rear muffler.

You still need an 02 sensor as well as all engine sensor operating. Catalytic converter removal changes the 02 sensor environment a little bit. Your 02 sensor more than likely mounts at the front of the catalytic converter on your 1991 240. So, replacing the catalytic converter mandates some sort of access for the 02 sensor.

I have read and heard from people that have removed the catalytic converter or destroyed it to reinstall a hollow shell have passed county and state mandated emissions. Though in these places the emissions limits were rather lax compared.

However, the Bosch LH fuel injection-emissions control system and the Bosch EZK ignition-emissions control system maintains good Volvo engine tune and economy and performance with all systems running optimally.

So, reference the response suggestions here to verify your 1991 Volvo 240 is running well running with all systems performing properly through your vigilant diagnostic and fault resolution efforts. Do your research. And get a service manual.

I think that covers it for you.

Questions and comments?

Thanks,

The Buttermilk "Fuzzy" Bombast.
--
Bombastic!

If he O2 sensor is not working, that will trigger an error code and the check engine light. Unplugging the O2 sensor will obviously do the same. The fuel injection computer uses the O2 sensor readings to measure the injector length, increasing/decreasing fuel.

One of the worst offenders of black soot is any vacuum leak around the intake manifold, which causes the engine to run rich. While these are hard to find, most of the hoses will degrade over time and should be replaced.

An exhaust restriction is hard to establish. An easier method is to make a fist and bang the converter with the side of your hand - cold exhaust of course! If it rattles inside, the converter is dead.

You could replace the converter with a straight pipe, so long as your car will remain in a non inspection area. The O2 sensor must remain in the system.
--
My name is Klaus and I am a V♂lv♂holic