Well we failed our CA smog today and could use some sage advice. It's a 1986 240/230F and is running well with all equiptment installed and functioning AFAIK. Car is running well, and did pass smog last year when we bought it. The results from today look like this..
%CO %O2 HC(PPM) CO% NO%
Max Allowed 133 0.82 1125/955
As Measured
15MPH 13.3 2.1 26 0.01 2055
25MPH 13.4 2.0 18 0.01 1855

The tech said that it is running lean and that this is related to the high NOX level. Car is running well...much better than when it passed last year, but apparently not good enough! Any help or DIY diagnostics or fixes to get the NOX done for the retest would be highly appreciated.

Thanks to all in advance!

Cliff

You have the Volvo/Chrysler ignition used on 240s from mid '81 thru 1988. It's been found that the V/C Ignition can contribute to high NOx, and that plugging the vacuum line to the ICU can reduce the NOx level with little effect on normal operation. Note that this is not a guaranteed fix, but worth a try if your other numbers (and cat) are good.

I first posted this (with source and technical description) on 5/21/04 (see original post. ) One person (CA) soon found that it solved his high NOX problem, and posted his happy response here, in the original thread.
NOTE that he had failed with a new cat, then plugged the ICU vacuum line, put the old cat back on and passed!.

Another success was posted in this thread. And yet another one here.

One person did recently report that this tip reduced his NOx, but CO and HC went up in this post. However, he also had some exhaust work done between tests, which may have been a factor. (A change in ignition timing advance should not increase CO and HC levels.)
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

" You have the Volvo/Chrysler ignition used on 240s from mid '81 thru 1988."

The Chrysler ignition (denoted by a white distributor cap) was used in '82 and '83 240 models. Starting with the 1984 model year and Bosch LH-Jetronic 2.0, Volvo appropriately junked the Chrysler ignition and began using Bosch parts again.

I believe you're mistaken. Only the distributor changed in '84. The basic system, including the ICU is Volvo/Chrysler thru '88.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Yes I have the red cap distributor and I believe the LH Bosch system. Can anyone suggest most likely causes for low CO%(0.01) and high NO PPM (2055
/1855) readings? It does look like I have a very lean condition...could this be my airmass sensor? Oxygen sensor? Catalytic Converter? As a died-in-the-yarn DIY type I am not keen to take it to a smog shop so that they can give me the big wallet flush...any suggestions or diagnostic ideas will be appreciated.

Thanks!

Cliff

Cliff,

My suggestion still applies.

Only your distributor is Bosch. The basic system, including the ICU, is the Volvo/Chrysler design. To date, there have been three successful NOx reductions reported, using this tip. Four counting the latest response with the anomalous CO & HC increases.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Lucid,

Ok thanks I will give it a try. From your description this fix requires that the vacuuum line which runs from the throttle body port to the vacuum dashpot/capsule at the bottom of the big plastic rectangular ignition module mounted on the front right be plugged or blocked off?

Thanks,

Cliff

Yes, as I interpret the source info (see original post link), the goal is to prevent the intake vacuum from influencing the ICU transducer diaphragm.

Just pulling the hose off at either end would do this, but the line must be plugged so as not to cause a vacuum leak.

My method would be to remove the rubber connector from the plastic line at the ICU end, fit a plug into the plastic line, then reattach the rubber connector. You could also do it at the manifold end, but the plug might get sucked out by the vacuum.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Red engines with high Nox are pretty darn common. Plugging the vacuum line to the ignition control unit may help, but it is tampering and a direct violation so just don't bring it up with the smog tech. While there is a functional test of your vehicle's static timing there is no functional test of how far it will advance or a check of the system to makes sure that it is getting vacuum where it is supposed to. So long as it passes visually it should be ok in that respect. Bruce is correct in his statement that your vehicle has a Chrysler ignition system, once they went with the Chrylser system they stayed that way until they went with the LH 2.4 injection system and EZK ignition.

Understand that what the techinician told you is basically right, you have a lean mixture or a hot mixture and that is what causes the formation of Nox. Your car is either sucking smoking hot air into the intake because of a faulty pre-heat thermostat or you have enough carbon on the piston faces to elevate the engine compression to a level that causes pre-detonation which will also heat up the air/fuel charge. I personally have seen some older 240s with 200-210 psi, that is way too much. As often is the case though you usually have a couple of things going wrong. I have seen lazy O2 sensors or ones that were biased lean that caused this problem as well. This is why diagnosing and repairing a problem like this is not easy and usually not cheap.

Something else to think about, was your car test-only directed? If so you automatically qualify for the state funded CAP program (Consumer Assistance Program). In this program you take your car to a Gold Shield Certified station and they work in conjunction with the state to fix your car. There is a co-pay of $100.00 and then the state picks up the next $500.00 and you are responsible for anything over that. If this sounds like something you are eligible for and/or interested in your test-only facility should have the appropriate forms to fill out and if not do a search online at the BAR website and they will have a list of Gold Shield stations in your area and they will have what you need for sure. It is kind of a pain to deal with but it is $500.00 worth of free money and if you need a cat you will burn up that money in short order.

As far as fixing it yourself goes, good luck. You can try a number of things, new pre-heat thermostat, plug the line, good gas, carbon clean the engine, etc but you will still need to see a smog tech with a dyno to do a pre-test on the thing or you will have to roll the dice and see if it passes on your free re-test you may have. Any way you do it tends to be a crap shoot and costs you money everytime you have it tested.

E-mail me if you'd like and maybe I can shed a little more light on it for you.

Good luck,
Mark

Mark,

I had already removed the preheat hose from the airbox so that is not the problem. I am going to give it a good going over to look for obvious problems. The car is running well and all tune-up items are about 12 months old and it was running so poorly when it passed last year the I did not do much (any) prep before taking it in this time. Yes it is on the yearly test schedule because readings were on the high side last year so it got pushed into that catagory. I saw the offer of state assistance for repairs...it is my son's car and he is poor student but it is still also in our name so I will need to see if there is an income test for eligability. As you say DIY is limited since you cannot test yourself for results so you are in the crap shoot scenario. Thanks alot for the good info, it was helpful.

Cliff

Just thought I would post a followup as I was able to get our 240 passed CAL SMOG today (whew!). Turned out the airmass sensor had gone bad..failed both tests in the Bentley. I put in a salvage spare and this one tested out of range, but not too far and the other one was just dead. I plugged it in and tuned it per the Bentley instructions for mixture. I also did the ICU/vacuum advance mod that was recommended, also filled up with premium. NOx dropped from over 2000ppm to 800 - 900 range and she passed...good for another year!

Thanks to all.

Cliff