Hi folks, I am a new user with a 1988 240DL that has 210k miles. After failing smog in CA with high NOX (1500-1900; the hydrocarbons and CO are fine, in fact very low), I have now replaced the catalytic converter, the O2 sensor, and the mass flow sensor, and welded up one or more exhaust leaks. The car was tuned up with new plugs and plug wires in the last year or so. It runs great, BUT is still failing smog even with the timing set all the way to the retard side at the distributor. I always run it with good quality gas. Any ideas?

I am running Lubro-moly, an MoS2 additive, in the oil. Wonder if it is masquerading as NOX?

thanks,
Jeff C.

 

Make super sure there are no exhaust leaks anywhere!
An additive shouldn't be affecting the smog but why do you use it? b230 with 210k on the clock should not be in need of any additives.

 

I agree with Lev in that any exhaust leak that is upstream from the O2 sensor can cause emission problems. Therefore you need to ensure zero leaks there.

Also make sure the EGR system is functioning properly. All California models had the EGR system while models sold in other states do not. If the tube running from the exhaust to the EGR valve is clogged, you can get high NOX.

 

Thanks lev and act. I had a few exhaust leaks plugged but am not sure just where the O2 sensor is and they might have been downstream; I will check that. My mechanic recommended the Lubromoly, curious why you say a B230 with 210k miles doesn't need it - I would have thought an older engine would. Or, is 210k not "old"? This car does not have an EGR. This vintage volvo seems to be especially hard to get through smog because it is "brittle" due to the lack of ***** to turn.

Jeff C.

 

we have a 87 240 with around 500k miles on it, still has good compression in all 4, has never had any additives, been run on a diet of 10W30 its whole life... originally I used castrol gtx, the last 5 years its had mobil 1. oil changes have mostly been at 5000 mile intervals, but sometimes those stretched considerably due to it being driven by other family members who neglected to tell me to do it.

 

Wow, 500k, Lucky you! I have always kept up with the oil, 5k at most. I take it you don't live in CA or have a smog test issue?

 

car has been a California car its whole life. a few years ago we needed a new cat. its had a few o2 sensors in its life (probably about one every 100k miles), worn out a couple alternators, 2-3 water pumps.

 

I had a similar problem a while back with an 87 240. After changing the Mass Air sensor I gave up on having independent garages look at it and I brought it to a Volvo dealership. They ran emission and told me it failed. When I told them that I had just put a new mass air sensor in it, they said "Oh, we will have to calibrate it then". It passed. I don't know for sure what they calibrated. I know there is an adjustment screw on the MAS. Perhaps it was this. Does anybody else here know about this?


After getting through this crisis I found an experience Volvo mechanic. I didn't have any more problems. One of the things he told me is that the engine has to get "good and warm" before running the emissions test. In New York, it is done by certified shops so they can get it warm before testing. I don't know about California.

 

Very interesting, I will ask about that calibration. My mechanic put a brand new Mass Airflow sensor on it, and it did not help so he took it off and sent it back. Wonder if he knew about this calibration business. I will ask, but I am working with a different (state-approved) mechanic now and if we simply cannot fix the problem, after spending enough money, I will get a two-year waiver. Wish I had started with such a shop then what I already spent would actually count towards that total. We are looking into this decarbonizing idea, with a Urea-based gas and cylinder flush, "Seafoam"is one tope of these. Opinion on this seems to be pretty positive online and from several mechanics I have talked to, but I have yet to hear from an actual user/customer whose problem was actually solved that way. Anyway, it is not expensive.

 

before I'd go overboard on 'decarbonizing', I'd pull the spark plugs and run a bore camera in there and inspect for said carbon. an italian tuneup (running the engine at 5000+ rpm in 2nd or 3rd gear for an extended run on the highway) usually does more than any bogus additives to remove carbon buildup on the valves and pistons... just make sure your cooling system is in good shape.

btw, you can check if your o2 sensor is working well. take a thin strand of copper wire, like one strand from a bit of lamp cord, an inch or two long. disconnect the round 1-pin connector to the O2 sensor, its right near the wiper motor on the firewall, and slip that bit of wire around the pin, and put the connector back together. set a digital volt meter for a low DC volts scale, like 0-10V or whatever, start the motor, let it warm up to operating temperature, and connect the red probe to that thin wire strand, and the ground to any reasonable ground. at idle, the voltage should swing from 0.1 or 0.3V to 0.6 or 0.8V, back and forth between the lower value and the higher value every 5 or so seconds. if you rev the engine up a bit, the swings should be faster. if you see that swinging back and forth, the O2 'Lambda cycle' is functioning.
if you don't, its not, and you might revisit that O2 sensor.

btw, what kind of cat did you install? was it a proper California CARB approved cat, or some budget hack ? Magnaflow CARB approved are about the only aftermarket cat I'd put on a car. The reason CARB has strict rules on cats is the market was flooded with useless crappyass cats that didn't work more than a few months. the CARB approved cats should last as long as the OEM cats did (a quarter million miles or more, as long as the engine is kept in reasonable tune).

 

Yes, that sounds like a good idea about the camera, I will suggest it, even though this is Silicon Valley I am not sure the mechanics have them, but they should of course. Cooling system is fine. Never overheats, original radiator was replaced 100k miles ago and works fine. The O2 sensor is brand new. It's a pretty good cat, a Walker 3-way, duly CARB approved. I did see Magnaflow, couldn't tell which was better, mechanic recommended the Walker. In fact, I probably didn't even need to replace it; I got burned on the first crappy cat some guy put in for me on the CA program maybe 8 years ago, lasted 2 years, tiny element, so I was suspicious of its replacement, got the Walker, but it seems that was not the problem after all. Oh well.

 

Hi folks, thanks for the ideas. I have had the seafoam/urea treatment and it did nothing, very little carbon buildup. The mechanic suggests two things: (a) he says some (not all) of the valve clearances are a little too large, meaning they stay closed too long, can make it run hotter. However, there is not a lot of valve clatter and they are not too far off. He is not optimistic about this. (b) he suggests the fuel injectors might be old and clogged or spraying poorly, causing a lean mixture, maybe they can be replaced. He is not optimistic about this either. My own mechanic favors the fuel injector solution. Everything I read online about fuel mix points to carburetion, not valves. Any suggestions?

 

Hi folks, thanks for the ideas. I have had the seafoam/urea treatment and it did nothing, very little carbon buildup. The mechanic suggests two things: (a) he says some (not all) of the valve clearances are a little too large, meaning they stay closed too long, can make it run hotter. However, there is not a lot of valve clatter and they are not too far off. He is not optimistic about this. (b) he suggests the fuel injectors might be old and clogged or spraying poorly, causing a lean mixture, maybe they can be replaced. He is not optimistic about this either. My own mechanic favors the fuel injector solution. Everything I read online about fuel mix points to carburetion, not valves. Any suggestions?

 

If you had injector issues, the car would be running crappy. You say it runs nice?
Do you test the emissions once the motor is well warmed up?
What are your actual readings before and after all these repairs? How close to passing are you?

 

Indeed it runs very nice, but I think Volvos like to run lean, and running nice doesn't necessarily mean running low NOx, at least as I understand it. At one point we intentionally delayed the spark as far as we could, and it ran with less power, but less NOx (maybe 1400, compare with below numbers).

the actual readings are very low in HC and CO, well below the acceptable levels, but the NOX is way, way high. To give you an example (with a brand new, Walker CARB-certified cat AND new O2 sensor), when we reset the timing to nominal, we got this (two different mph ranges):

HC(ppm): 11-14, max allowed=60-80
CO (%): 0.03, max allowed=2
NO(ppm): 1850-2280, max allowed 500-760.

Looks to us like it running way too lean and hot. Very little uncombusted C and huge amounts of NO produced.

 

Take a look at this, I had it in my files:

"I assume the readings are taken at the tailpipe, after some of the free O2 has been used to oxidize CO and HC, so the level at the input of the converter is probably even worse. I am also concerned by the low CO2 reading at 15 mph; readings below 13% indicate dilution - too much air for the amount of burned fuel. The spectacularly low HC and CO levels confirm there is plenty of free oxygen present.


The next thing I would go after (and my top suspect) is the mixture. The mixture probably is actually lean, so far lean the O2 sensor probably stays near 0 volts 100% of the time. I believe your 1988 240 has the L-jetronic injection system. Some of those have an adjustment on the MAF sensor and there is a two pin diagnostic connector - mine was on the passenger side in my 760 - that should swing in voltage when the system is in closed loop (O2 sensor controlling the mixture). A cleaning of the MAF may be in order, too, because if dirt has built up the sensor won't detect the air flow well. In addition, if there is a leak in the ducts between the MAF and the throttle body the mixture will be lean. That won't show up as a vacuum leak or even as really bad symptoms. A look at the spark plugs should show whether it is running lean most of the time - if the insulators are bone white the mixture ain't right.

One more thing - it wasn't mentioned in the list but I'm sure the timing was checked. Advanced ignition timing will make your readings worse (if that is possible!)
Source:

http://www.bearriverconverters.com/data/...
35 years maintaining my own cars, including 17 years with a 1985 Volvo 765T

 

Thanks. The ducts between the MAF sensor and the throttle may not have been looked at for a "non-vacuum" leak. I will ask. They did first clean and then actually replace the MAF sensor entirely with a new one - no change, so they sent the new one back. I do not know if he actually did the diagnostic to see if the O2 sensor was cycling properly, but he did replace it. We have had the timing backed off as far as possible on nearly all these tests, too.

The "spectacularly low" NC and CO is sure another clue about a too-lean mix. One mechanic told me that messing with some of these other things can actually be offset by the computer, that is trying to achieve a balance that it thinks is perfect, but might be too lean, so it might negate whatever we try to do. He was, however, not optimistic about replacing the computer.

 

Jcuzzi,
Did you ever get your car passed through CA emissions?
Your low CO and HC reflect a good running engine but those NOX levels could go right back to that CAT.
Just interested in your results and what fixes had to be made?

 

Had the engine "decarbonized" with a "Seafoam" like product, as several people suggested - no gain. It was already pretty clean. One mechanic suggested replacing the fuel injectors, they might be spraying too lean, but another says the computer should take care of that. Another mechanic suggested a valve job, there is a little play and they are staying closed too long, he thought that might run it too hot, but he was not optimistic about that and neither am I or my normal mechanic. Still thinking.

 

I doubt that it's your injectors. Also I doubt changing/adjusting your valves will help either. Just scanned through your entire thread and I didn't see it stated that you had your MAF adjusted when it was installed. Has this been done? Also it wasn't definitively stated that the it was checked for exhaust leaks upstream of the O2 sensor. Read this post from Brickboard

https://www.brickboard.com/RWD/volvo...ual_cause.html