1994 Volvo 940, well maintained, but sits a lot. I only drive it maybe every two weeks. It runs well. Anyway I drove it a 100 miles the day before smog check, but only maybe 20 minutes on day of smog check, which I failed due to High HC.

Spark plugs have 15000 miles of service on them. Cat is original.

So after the failure, the smog guy said to drive the car maybe a 100 miles over a week and then come back. Any thoughts on this advice? Or is it adequate to really ring it out just prior to the test?

Any thoughts on fuel additives, premium gas before the test?

Thanks.

are there any holes in the exhaust close to the cat&the oxygen sensor??

In some states cars that age are exempt from emissions test.

Yup, in Mass cars more than 15 years old don't require an emissions test. They do, however, require a safety inspection.
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Will I buy another Volvo??? We'll see....

1995 model years back to the car being 35 years old (1985) require a safety inspection and a "visual only" emissions inspection. They look for the presence of cats, etc.

More than 35 years old -- no inspection at all. My 1982 242 'graduated' 3 years ago.

...and for OBDII (1996 and newer) they simply look for codes. No codes = emissions systems doing its job. Why would any state still be sniffing tailpipes....

You failed the CA-state SMOG inspection for high hydrocarbons (HC).

And is Non-Turbo, yes?

Helps us to know the values for HC, CO, and NOx on your failed test report.

FAQ entry on high HC (copy and paste link into new browser tab or window):
https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#EmissionControlProblemsHighHCCOorNOx

High HC suggest an:

- excessively lean running condition (You may hear valve ping)
- excessively high engine combustion chamber temps
- exhaust leak very high up as where the exhaust manifold seals against the cylinder head or the manifold to header pipe
- Weak or failing oxygen sensor, maybe
- Weak or failing catalytic converter that can also run too hot in a lean (and rich) running condition
- EGR Valve stuck open at all times, yet if open you'd know with terrible engine running conditions.
- AMM / MAF is somehow faulty.

EGR is to reduce NOx. If EGR is clogged, not much effect on HC. Yet DTC code check can maybe find an error that, with other DTC indicated faults the Bosch engine control encounters through connected sensor and devices.

Have you checked the OBD engine DTC fault codes?

Has the FPR ever been replaced? One of the FPR failure modes is stuck open, so low fuel rail pressure at all time as if you are driving it yet no foot on the gas pedal creating a high manifold vacuum.

Is the silver accordion hose connected between the exhaust manifold heat shield and the air filter box? On a non-Turbo with LH-Jet / Motronic & EZK ignition, the air filter box inhales preheated air so the AMM / MAF is warmed so fuel trim and emissions are controlled. Inside the air filter box is a air temperature thermostat (Wahler PN 704110 is after market, unknown who makes the Volvo PN 1266826 version). The thermostat fails and when it fails, it all preheated air all the time and may also cause high HC before the AMM / MAF fails.

Have you tested your oxygen sensor using a digital multimeter as described in service manuals and the FAQ here:
https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#OxygenSensorLifeandDiagnostics

What sort of driving every two weeks do you do in your 940? If your 940 driving habits prevent engine oil sump and exhaust including the catalytic converter from warming fully emissions control performance may be compromised. So, yes, an Italian tune up. I've never needed to perform an Italian tune up.

How many miles? A well-tuned non-Turbo redblock with LH-Jetronic on the late 1980s-1990s may use the same catalytic converter from the factory. Yet these can fail, yet for the price of these, perform your root cause analysis.

Another check is to compare exhaust gasses at the header pipe bung (if not rusted to uselessness) upstream of the catalytic converter. There exist specification for what the catalytic converter can eat versus the transformed (cooked) exhaust gasses the catalytic converter exudes. Sort of what the oxygen sensor would do, yet the oxygen sensor is there so engine control can measure the exhaust gas oxygen count. Too much oxygen, engine control makes a richer mixture. Too little oxygen and engine control becomes lean.

All I got. Hope that helps.

Selling my Lionel 027 Model RailRoad layout to pay July rent as the secret society continues to prevent me from employment in dog awful Saint Louis MO.
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Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity!

Non turbo. 225,000 miles. It failed only 15 mph HC. Max permitted is 59; I scored 114.

The silver accordion hose is intact. I have not checked codes, but engine runs great.

This car sits a good deal. And it was not that warm when I did the test. My cheap and lazy prescription to date is to run the CRC Guaranteed to Pass Emissions magic snake oil through the tank, and to drive daily at high speeds/revolutions. Then I will retest.

Does anybody know how many miles the catalytic converters can be expected to last?

Thanks for all of your responses.

In my experience catalytic converters in Volvos last a very long time. Maybe the life of the car?? Replaced the cat in my 90 244DL at around 250k. The cat in my 95 855GLT was still going at 250k when I sold car.
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Will I buy another Volvo??? We'll see....

Mine lasted about 150k miles that I know of ... right up until I smashed it on a fallen rock Hahaha.

That will do it....:)
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Will I buy another Volvo??? We'll see....

Just to close the loop on this, my mechanic experimented with new O2 sensor, Seafoam, etc., and finally ended up putting on a new cat.

Volvo cats for CA are unavailable. So I went for a supposedly bolt on Magnaflow for $500, which was 1.5 inches too short. Mechanic had to add a sleeve to make it fit.

I did however, pass smog successfully.

Thanks all for your suggestions.

Buy some Seafoam and introduce the liquid into a warm engine by slurping it into a vacuum port with a length of tubing, keeping the engine running. Turn off engine and let it sit /soak for 15 mins. Start car and drive sporty (It will Smoke 5-10 mins). Now replace your O2 sensor.


-Seafoam read the Label-

Thanks, all. So after running the CRC Guaranteed to Pass snake oil through, I did a retest and still failed. The numbers were much better than before, but I still failed by 2 points.

At this point I am starting to run out of time. I will be bringing this by to my mechanic to see what he can do.

For some reason I always believe you are in CO-state. Yet where do you dive in CO-state? Some high mountain valley fresh water lake? Spear some trout and grill it out!!!!

Lats Bay Area dive for me was at Monterey Bay.

Have you checked the Bosch engine control (or management) for any set DTC codes? Copy and paste the URL into new browser window or tab. Or (right or Shift+) click the FAQ:

https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

Perform the "1. Diagnostic Test Mode 1: Fault Code Retrieval" fort socket 2 (Bosch LH-Jetronic 2.4 and newer, or maybe Motronic on your 900?) and socket 6 EZK116 ignition.

If the red light flashes out a code OTHER than the "all is probably well" 1-1-1, record the DTC (diagnostic trouble code) and repeat until no new or different codes display.

Of course no CHECK ENGINE light on the instrument cluster. The technician would fail you immediately in Cally-state during the SMOG test.

Inside the air filter box, did you check the action on the preheater flap valve? Is it stuck to all hot all the time? They won't open the air filter box yet you can force to remain at cold air inlet only and block the hot air inlet. After 26 years, the factory air temperature spring action thermostat fails to all hot air through that silver accordion hose. When the MAF / AMM fails, into limp home mode foes engine control, making for a rich fuel to air ratio. Rich ration is high in CO and lower in HC.

If you use your repair service technician, that individual can also check the codes (at USD$100 hourly).

You can also test the oxygen sensor. I posted this info for you before. Have you tested the oxygen sensor action using an electric digital electric multimeter. How to test is in the FAQ.

FAQ entry on high HC (copy and paste link into new browser tab or window):
https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#EmissionControlProblemsHighHCCOorNOx

If your repair technician has a exhaust gas analyzer, test the exhaust gasses upstream of the catalytic converter. Yet I do not know the PPMs of each. I guess 1.0$ CO or a little lower?

Does the exhaust smell dry and sort of sweet or rich with gas smell?

Else, other than verifying all of these items, and verifying the exhaust gas upstream of the catalytic converter, the quickest way is to replace the catalytic converter with new so the fresh and new cat scrubs and reacts with the exhaust gasses to convert to the downstream exhaust mix so you can pass emissions.
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Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity!

Basically, my mechanic has tried all the cheaper alternatives such as O2 sensor, Seafoam, and changing AMM. No dice.

Does anybody know of a good quality, bolt on, aftermarket cat approved in California? Otherwise, I will have to go for a weld on mufflershop special

Thanks.

California does not allow aftermarket cats. All replacements must be OEM/dealer supplied.

If you are in the driver's seat when doing the 25mph test, move the gear lever to 3rd gear. Remember, the engine needs to be completely warmed up before the test begins.
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Keeping it running is better than buying new

I had a Dodge Dakota that was always slightly failing or barely passing the smog checks. One day it failed and the test operator showed me a little trick that got the numbers back into the pass range. He said to lock OUT the OD so that when you do the 25 MPH dyno test the engine will rev higher but with less throttle load. It worked. I guess that allowing the vehicle to shift all the way up into OD at 25 MPH on the dyno just isn't a real life situation that you would normally encounter when driving down the road.

Get the engine really warm first then do an "Italian tune up" on it. Afterwards drive it immediatedly to the test center.

Have no experience with the "pass emission in a bottle products" Very skeptical....
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Will I buy another Volvo??? We'll see....

What does the inside of your tailpipe look like?

It should be a nice tan color.

If it is black, you ARE running rich.

Check your air cleaner. If it looks dirty at all, change it (You could remove it , vacuum out the box and get the test without one if you are REALLY cheap!)

You could also have some foreign material in it - like a mouse nest. Once, the foam rubber on the top of the air cleaner box of our '90 744TI failed and clogged the air cleaner.

If you haven't kept up, bringing your car up to stage I could solve the problem - bringing the maintenance up to snuff, especially ignition tune-up.

One of the problems with our Volvos is that they can compensate for age so well that they do not break down even if we do not take care of them.

Leaky injectors.... Also check your fuel pressure regulator.

Check your vacuum lines for leaks, the low miles and lack of humidity will cause cracks.

Have you checked the EGR? The port to the intake manifold clogs easily when not driven a lot.

Driving 100 miles in a week doesn't do much, unless it really gets the engine oil HOT.

I would replace the plugs (copper core) or clean and gap the current plugs. Then get the engine hot. Drive to the testing station, do not turn the engine off, and let them test it again.
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Keeping it running is better than buying new

I HAVE A 1995 960 THAT ALWAYS PASSED THE TEST BUT THIS YEAR A STAR TEST AND IT FAILED. TOOK IT IN AND MECHANIC SAYS ALL FINE. BUT THEN WHEN ASKED ABOUT SMOG TEST SAID
USE PREMIUM GAS, DRIVE HALF HOUR AT FREEWAY SPEED
THEN TAKE IT IN.
HAVE TO TRY THAT???