Hello all!
A few weeks ago I bought a mixed bag 1993 volvo 240 wagon. A few months back the PO had the catalytic converter cut out and stolen so I have a big section of piping totally missing with a couple hanging wires. I'm right on the brink of going over budget on startup costs on this thing and I am seeking advice on what the cheapest way I can patch this up while maintaining full driveability.The issue with installing a new cat is the price of parts along with having to have new flanges put on the cut pipes is going to overshoot what I budgeted to get this thing driveable as I cannot weld. I'm in an area without emissions testing and I have a good muffler shop nearby that could weld in some pipe for about 90 bucks but I'm concerned about the missing O2 sensor causing running issues. Is there a way to keep the fuel mix right without a cat? Can I just straight pipe it and tap some threads for a new 02 sensor?

 

Just have a pipe with a o2 bung on it welded in. Put a plug in the o2 hole and drive the car. The o2 sensor does very little and can't change the mixture very much. Its function is to make the mixture perfect for the cat to be most efficient, not make the car run good. And you won't have a cat. Most older cars can easily run fine without them. If you find you don't like the way it runs and insist on putting an o2 in - you've got a spot for one.

 

Sounds like a solid plan. Thanks for the advice!

 

if you live in California where they smog test cars 1975 and newer, you will NOT pass the tailpipe sniffer tests w/o a functioning cat and o2 sensor.

any muffler shop should be able to weld in a aftermarket quality cat like a Magnaflow or equivalent, with a bung for the o2 sensor. Our 240 got around 350-400K miles with its original cat before we had to replace it to pass smog

 

I based my response on the OP's parameters. I do not in any way advocate or approve of modifying or deleting emission control devices, but I do understand lack of cash being a very important parameter.

 

I appreciate all the input! I do plan to get a quote on what an aftermarket cat would cost but If it's too much I'll be alright with straight piping it. My only other question is if I am to go without the oxygen sensor, what should I do with the old cut wires? Cap them off and tie them up or connect them to eachother?

 

Aftermarket CATs aren't horribly expensive and I believe come with a 6 year warrantee per regulations. I put one on our 240 and it cost somewhere around $125 - $150 and I did the work myself. Even if you put a straight pipe in it would be best to weld in a bung for installing the O2 sensor just as Honk recommended. You will need a new O2 sensor which will come with new wires. Without the O2 sensor your engine will run in open loop mode meaning it uses a fixed map for fuel. It will run rich and your mileage will be poor and you check engine light will come on.

 

What you're proposing is known as "installing a defeat device", is illegal everywhere in the United States, and has been responsible for some of the largest civil fines in the history of litigation. Granted, you're not going to earn an $83-million fine for installing a defeat device on one vehicle, but the enforcement environment shouldn't be ignored.

This one would be glaringly obvious; the vehicle won't even pass a simple visual inspection.

I'm not very good at predicting the future -- my crystal ball is overdue for its 5-year, 5000-prediction overhaul -- but I think it's safe to say that emissions enforcement isn't ever going to become more lenient. It may become impossible to register, license, title or sell a non-compliant vehicle.

Without an O₂ sensor, with an engine running in open-loop mode, an engine will foul the cylinders, lubricating oil and spark plugs with unburned gasoline and excess carbon. The 7500 or 10,000-mile recommendation for oil-change interval will no longer be applicable; oil changes will be needed every 3000-5000 miles and it'll need valve & ring jobs every 100,000, same as if the engine had a carbonator instead of closed-loop fuel injection. Cleaning or replacing the plugs regularly will also be required, to prevent misfires. Excess NOₓ formation (due to lack of precise air:fuel mixture control) may lead to excess nitric/nitrous acids in the exhaust, (NOₓ plus H₂O) causing excess corrosion in the exhaust system.

https://www.epa.gov/enforcement/mack...ine-settlement (1998)
https://en.wikipedia.org/wiki/Volksw...ssions_scandal

 

"10,000 mile oil recommendation"? If you follow that you will need a 100,000 mile valve and ring job anyway! A lot of theory, little practical value...

 

The owner's manual for my naturally-aspirated 940 (B230F) recommends a 10,000-mile/one year oil-change interval. Nothing personal, but I'm going to pay a lot more attention to the manufacturer's engineers than to random Internet trolls.
I've been changing oil once a year since 2005.
With almost 300,000 miles, the compression's strong & even, and the engine runs well and idles smoothly.

 

available with the pipe..
https://www.ebay.com/itm/Catalytic-C...YAAOSwVjheLy9Z

 

I bet he needs the downpipe (and the O2 sensor) also ---

 

We can argue about oil change intervals forever, the oil change industry wants to sell oil, the car makers want to sell new cars so each is speaking with their own interests in mind. The B230 is robust, probably as forgiving an engine as you can find, so you can get away with dirty oil but once you get a more modern car, a turbo, a multi valve head, etc, a 10K oil change is excessive. I like to push the envelope with maintenance but with oil I think 5k is a good distance even with the B230. Oil that has gone 10k just doesn't feel, look, or smell right to me, the viscosity is gone!

 

I'm sure you could, but try not to lose focus and start yammering on & on about irrelevant stuff. The question is whether to re-install a catalytic converter and O₂ sensor on a 1993 engine, or not. That is the question. Nobody's talking about a more-modern car or a turbo, and whether it has two valves per cylinder, or more, has no influence on anything.

Disabling closed-loop operation and abandoning precise air:fuel mixture control is unlawful, will lead to increased contamination, and invalidates the manufacturer's oil-change-interval recommendation. Whether that's a good tradeoff is an individual judgment call. That is all that's relevant here.
Well, as long as your opinion is supported by testing the oil's look, feel & smell, (not to be confused with laboratory testing of the actual viscosity, base number, metal content, fuel contamination, water/emulsion content, et al.) I yield to your expertise and disregard what the Volvo engineers wrote into the owner's manual, which has served me well for the last fifteen years of a 27-year-old engine.

 

maybe so, when i replaced my original downpipe there were many many pinholes in it that were not very easy to see...

 

Usually when converters are stolen a sawzall is used to quickly remove it - the easiest place to cut on a 240 is the downpipe and after the converter. - So you have no flange to bolt the new converter to -

 

yeah those devils use battery operated devices and not much care where they cut for their prize...
bless their little hearts...