Failed emissions (on NOx) by a hair. CT state emissions test.
Other pollutants well within OK range.
Had tranny fluid leak spraying onto exhaust pipe near cat converter and O2 sensor.
Fluid leak is now fixed.

Car is normally fed on 89 octane.
What octane should I feed it for the retest??
Has new 92ºC thermostat.

Good independent Volvo specialty shop found no apparent problems in fuel/ignition system while doing tranny leak fix. Recent tuneup, good hoses, etc.
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Formerly Sophie's Maintainer. Sven: '89 245, IPD sways, E-fan conversion, 28+ mpg - auto tranny. 850 mi/week commute.

I agree it may be the cat but it may also be the o2 sensor and/or air mass meter. My Volvo factory service manuals call for 93 octane for the U.S. B230 engine. I did not know this until I bought the manuals. It explained why I got a knock under acceleration up hills despite having a maintained engine. Since I went to 93 octane none of my Volvo's ping or knock anymore. A new cat will run you between 250 and 300 plus instalation.

I've been through NJ's (dynomometer) testing on all of my 240 cars, and over the years I've found that it's typical for a 240 to eventually fail for excess NOx due to a failed Cat (they don't last forever). Then I get a new Cat installed (nothing else done), and the car goes through and passes clean! See below.

It's not the cheapest fix, but it has seemed to work for me each time -- four 240's so far, over the past six years. At least after you get a new Cat, they're good for a while -- the Cat's should last ten years or more.

Example, my '84 240 got a new Cat in '02 (in order to pass that year's test), and it's latest test was in '04 (when it had 193K miles), where it scored (on the N.J. dyno):
NOx = 33 (1227 was the standard)
HC = 27 (162 was the standard)
CO = 0.02 (0.91 was the standard)

I can't say that you'll be as successful, as your car may also need other work done (I keep mine in good shape, continuously), but if the other fixes don't work for you, consider a new Cat.

Run a couple of tanks of 91 octane. Take your car out for a drive for 1/2 hour before the test.

I don't know if it will distinctively make a difference -- however, I would nonetheless run the highest octane of a fuel that is known for low emissions --such as Chevron Techron.
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dnvolvo 89 765T 200k - 91 245 100k

I have the same problem, but so far I got nothin'. (I have a 940 turbo, but same basic issue)

If it helps, see my post with a similar question.

Ian


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Re. your question in noted thread re. diagnosing knock sensor -

For what it's worth,
The knock sensor retards the timing some (apparently up to 10º) when it detects knock. I'm told it's basically a block-mounted microphone.

Timing changes will strongly affect emissions. Sensor reading incorrectly could certainly affect emissions.
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Formerly Sophie's Maintainer. Sven: '89 245, IPD sways, E-fan conversion, 28+ mpg - auto tranny. 850 mi/week commute.

Thanks for the tip,

I did swap in a known good knock sensor and there was no change. Also changed plugs/dist and cap, so I am confident that is not the answer.

Ian


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The knock sensor wont do a thing during the emmision testing unless they are flogging the car on a dyno for the test. I would suggest running the car down to about 5 gallons of gas and then adding say 1/2 to 1 gallon of methanal (or ethanol is you can find any) to the tank . Drive the car until it's good and warm (a few full throttle blasts to get that old cat cookin') then have the test run. The alcohol will emit other pollutants that the machine is not looking for and the car will probably pass - this time. Now you will have the time to fix the car so it will pass next time. Better yet get political and get the stupid law changed.
Steve

Speaking for myself, I think the law is fine. Further, I am glad I am able to identify a problem I had not previously know existed.

Tricking the test does not make problems with how your engine is running go away.

Of course, this might be easier for me to say as I actually passed the test by a few ppm.

Ian

Check this posting regarding NOX ... it may help.

http://www.brickboard.com/RWD/volvo-899304.html

I did that last year & passed w/o a problem

I might just go that route! (plug, that is)
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Formerly Sophie's Maintainer. Sven: '89 245, IPD sways, E-fan conversion, 28+ mpg - auto tranny. 850 mi/week commute.