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240 Failed HC twice

Maximum Turtles

New member
Feb 18, 2014
Santa Rosa, CA
1992 240 B230F NA, automatic

It's smog time again, and this time things aren't going as smooth as usual. I took it in for the check and I failed for high HC @ 15mph, and passed but barely @ 25mph. NO and CO are both good, so I suspected ignition. I replaced cap, rotor, Volvo OE plugs and wires, checked manually for spark at each cylinder, check ignition coil resistances and decided I was probably good.

I drove the car real hard for about an hour, then brought it in for retest:

>Smog Results<

This time it failed EVAP and he noticed the preheat hose has been missing for 10 years. Got those replaced, but HC hasn't budged at all. What else can I look at? I'm on a really tight budget right now and I'm hoping the oxidation cat or oil leaking into the cylinder aren't the only solutions to this. Any ideas?
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Change your air filter and change your oil. Then have it retested somewhere where they won't put you on the system to check your car. With that many miles I would also suggest use a slightly thicker engine oil. Like 10-40W for example. Also make sure your pcv system is working well.
Should've also mentioned new (within a month) 15w-40 oil and air filter, and I cleaned the PCV at the time. Just rechecked PCV though, all looks in order. I don't know of any shops around here that will check without charging full price for a test and putting it in the system.
When you changed the plugs did you check the gap? They usually are correct from Volvo but I don't trust anybody now and always check them. Set them for .028". That's too bad about the shops. IIRC one of the members here is a inspection officer. I don't remember his user but hopefully someone will chime in.

If you can use a meter. You may want to check the resistance of the new plug wires. I've had brand new bougicord stuff be bad. What failed for me was an engine rpm sensor bad right out of the box. I've never been impressed with Volvos choice of oem wires. The have always seemed to me to be bought more for savings than highest quality. The stock spec for the wires is 500 ohms per ft.
I would find an inspection place that takes "Appreciation Gifts"

Up here in BC, Canada, we used to have Aircare inspections. We also have snow. Aircare had a policy that they would not run studded tires on the rollers of the dyno, as it damaged the rollers and the studs would pull out and fly around sometimes. If you had studded tires installed, they only tested for idle........ I used to have a set of crappy studded rears on rims I got for 25 bux on craigslist, and I would throw them on just for the test and always go in winter (studs are illegal in the summer here). My 82 turbo failed regularly before i got the tires, specially after a mod or two. Never a problem with the tires on.
Ironically my 79 242 - b21A with an SU carb and all the smog stuff stripped passed every time summer or winter once i figured out the previous owner had installed the distributor one tooth off. It would get real close to timed right, but not quite. I fought with that issue for a long time before i figured it out. That caused 2 fails when I first got the car.

Interesting that trucks 1 ton and over were exempt so if you wanted to build a rat rod/hot rod with a smokey carby engine, you started with an old 1 ton truck cab if you could find one. 32 chev sedan with a blower and carbs, good luck passing, same motor in a truck, no prob.

Ironically in todays day and age of EFI and cars going into limp mode when the emissions got out of wack, nobody was failing anymore so they scrapped the program because it was unnecessary. All the old smokeys had already been pulled off the road.
I may become a smog repair and/or inspection technician soon. 5 gas analysis can be tricky. I would like to get better at it, but it's becoming obsolete. Its also not as straightforward as many think.

High HC is unburned fuel. You could have a little bit of misfiring, or maybe your cat is just tired. These aftermarket little kitties aren't the best as cleaning up old tractor emissions for years/decades.

Resize that pic, or this thread will suck to read for many.

From my experience, throwing a nice new cat in there has gotten me thru CA smog 90% of the time on my LH2.4 cars (with EGR). I mean, your CO is passing, it doesn't look like you aren't way rich, or lean.

Here, look at this thread where I was very successful in passing smog with a fresh kitty in a 1990 240 (LH2.4):


And on the other hand, here is a thread where I had mixed results with a 1986 740 (LH 2.2) The numbers were wildly jumping over the place sometimes, but the car drove fine. Such as the time when CO showed 6%!!! 6x times the limit=very rich. I finally passed, once, but not shown in the thread is where I ended up failing again later for evap and HC so I crushed the car.

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I did gap the plugs. They were pretty wide when I pulled the old ones out (.036"), but I gapped the new ones to .030". I didn't check the resistance of the wires, that's good to know that the bougicords can be crappy.

I'm pretty certain it's the oxycat at this point, especially with how well the engine is running. I found a CARB cat and a shop willing to install it on the super cheap, so I'm gonna try that out. I'll let you guys know how it goes, thanks.
Bougicord wires are great. I wouldn't put too much faith in resistance specs.

Which cat do you have on there now and how old is It?

A three way cat cleans up all THREE pollutants.
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It will be interesting to see results but I'm sure from what I see here that little bit over range of HC will probably be taken care of with a new cat. Although usually what I've experienced here in NJ is the NO going high as the cat fails. But as Z mentions it is a three way catalyst.
I found a CARB cat
Just went thru this. The CARB approved cat I bought, caused a fail due to its part number! The '87 765T (pre-OBD1) 'sniffed' like a new car, though.

The cat itself is from MagnaFlow (enclosed warranty card from them), bought thru FCP online, but DEC did the final assy using the Maggie cat, making it a "direct fit". The smog guy showed me a pic of the cat PN and copied the applicable page from the Air Resource Board. One tech at MagnaFlow was superb, telling me the whole story, allowing me to save the car.

The short version is: procedure calls for the smog shop to check the etched or placarded PN on the cat, then check it against the year/model/engine in an online database.

The cat I bought is legal on a 760 six cyl., but not on the turbo 4, per his referenced page. However, another ARB page (per the Maggie tech) showed this cat legal for this car, which the smog guy verified with a referee. The cat itself, when referenced in a different column (for many cars, actually), IS LEGAL. The in/out pipes make no difference in emissions, but final assemblers assign differing PNs.

In my case, DEC did the final assy, but their PN was not only wrong, but caused the fail, due to the PN they etched on the assy. See, it showed as a universal cat, but is actually a direct fit (bolt-in). A pal in the biz told me DEC lost their CARB certification, but now regained it.

I'd opted for a higher quality, more expensive cat than the little cheapo I removed, being told that the cheapos are good for about two years, while the better ones last much longer (assuming proper tune, etc.) In this case, size can matter! The much smaller cheapo I removed had melted material inside, due to incorrect fuel burn, causing it to overheat.

I suggest you consult the ARB page that lists your car and the cats that are approved, before you shop, to minimize headaches or worse! Often cheap, isn't, as in this case, where MagnaFlow's support saved more costs. etc. FCP's support was pretty good, too.
Super passed! single digits HC and NO, CO was .06.

Whalepirot, that's good advice! I did look before I bought, but a lot of people will no know to do that. I found mine for $30 in "used" condition on amazon (welding had been done to it but it was never installed) and all the shop ever checked was if the PN matched the car in the CARB database.

Technically they are supposed to diagnose the bad cat themselves if they install it and they aren't allowed to use exhaust pipe size adapters, and they can't install used, but if you call around most exhaust welders don't take that stuff too seriously.

Thanks for the advice as usual, everyone!