SwedeSpeed - Volvo Performance Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
80 Posts
Discussion Starter · #1 ·
Hey all,<p>In the lovely county I live in, we have emissions testing for cars that are under 25 years old. Bottom line: this is revenue generation for the county and a way to get older cars off the road (not htat they're going to help me pay for a newer one!).<p>I have a 1991 240 sedan automatic, with 206K miles on the clock. It runs beautifully, but last year, I barely passed the NOX part of the emissions test by three points.<p>This past year, I have relegated my beloved 240 to third car status and it does not get the daily grind commute. I am betting since its not getting driven as much, this car will probably not pass emissions testing this year.<p>Does anybody have any experience in diagnosing what causes high NOX on emission testing?<p>I hate to go in and start replacing the cat and 02 sensor and other things not knowing exactly what causes high NOX...that seems wasteful.<p>Anybody have any suggestions as to what to do, proir to emission testing? I really want to pass and not be out of inspection or have to wind up ditching the car, only because it does not pass their one silly test. It runs great.<p>Thanks in advanc for the advice.<p>- Brickboy240<p>PS - if I have to replace the cat converter (a very real possibility, because I still have the original unit in this 91 240)...where can I find a quality unit for cheap?
 

·
Banned
Joined
·
1,241 Posts
Re: :confused: what to do in order to pass emissions test this year??? (brickboy240)

VolvoGuy recommeneded to me, when my parents 850 scored high on the NO-though it still passed, that I should clean the Throttle Body. Hope this helps <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/smile.gif" BORDER="0">
 

·
Registered
Joined
·
212 Posts
Re: :confused: what to do in order to pass emissions test this year??? (brickboy240)

Hi:<p>Try this first:<p>- Clean throttle body.<br>- Fresh oil & filter change.<br>- New flame trap and any cracked flame trap hoses attended to.<br>- New air filter.<br>- Warm car up VERY well before taking in for emissions check.<br>- Do not take car in for emissions if it is raining, period. The cooler temp can make some readings higher.<p>Usually, a 240 with these issues handled (which are routine maintenance anyway) will pass unless there's a real problem somewhere, like bad engine wear or a cat or 02 sensor. If you need a cat, buy it from Volvo or from IPD or FCP Groton; the fit is critical. There are different-sized units for different years, etc.- you have to measure to get the right unit. If you get a universal unit, you'll have exhaust issues from then on, trust me. The correct cat is around $200, not the most money you ever spent on a 240, right? <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/tongue.gif" BORDER="0"> Sometimes OEM Volvo cats show up on eBay for less, but you have to know what you're doing to order the right one, and to install it.<p>P.S.- If you're in California, you need to know that some 240 readings are just barely legal, even if the car is in showroom-new condition. Cali's emissions laws are damn tough.
 

·
Banned
Joined
·
3,169 Posts
Re: :confused: what to do in order to pass emissions test this year??? (brickboy240)

Based on your description of the problem (high NOx, presumably low or acceptable CO and HC), my first inclination would be to suspect a very lean fuel mixture, possibly occuring in conjunction with a cooling system fault. <p>Although a vacuum leak downstream of the Mass Airflow Sensor (MAF) could lean things out a bit, a well functioning Heated O2 Sensor (HO2S) should be able to compensate by increasing injector pulse duration once the engine has reached normal operating temperature. With the fuel system regulated by the fuel pressure regulator to work at 43 psi, a pretty fair amount of fuel can be dumped into the cylinders to compensate for minor vacuum leaks.<p><br>As I'm assuming that you've done the normal maintenance stuff like new plugs, wires and air filter, you may wish to concentrate on the following:<p>a. look for a major vacuum leak downstream of the MAF. This could consist of a cracked or broken hose or bad gaskets (throttle body or intake manifold gaskets). An easy way to find a leak is to use a handheld propane bottle with a regulator and hose. Don't ignite the propane, just crack the valve until a moderate stream of gas exits the hose. Start your engine. With the engine idling, guide the open end of the hose around the outside of the throttle body and intake manifold, concentrating on the joints. Don't forget to check under the intake manifold in the vicinity of the Idle Air Control Valve. When the idle suddenly increases, you've found a leak.<p>b. examine the fuel pressure regulator. Frequently the small hose that leads from the intake manifold to the regulator cracks. When this occurs, the regulator operates at reduced efficiency. The result is lower fuel pressure across the rev range. Less fuel = leaner mixture.<p>c. remove and clean the throttle body (use a throttle body cleaner that is safe for fuel injected cars or those fitted with O2 sensors);<p>d. check the throttle position sensor. Rotating the throttle pulley a few degrees from its rest position should yield a faint, but audible "click". This click is the switch that tells the ECU that the car is off idle and it's time for the engine to be operated on a driving map. If there is no click, adjust the TPS using instructions provided in your Haynes or Bentley manuals.<p>e. check the ignition rotor and distributor cap. Internal carbon arcing or terminal wear can upset ignition timing. If you haven't replaced these components, do so... they're regular service items. Don't worry about setting the timing -- it's automatically controlled by your car's spark computer.<p>f. check the HO2S. There are many sites on the net that explain how to do this with a simple Volt-Ohm Meter; <p>g. check the EGR system. An EGR stuck in the "open" position can lean-out the fuel mixture; and<p>h. check and record any fault condes contained within the ECU. Details on how to do this can be found through a SS search or by Googling on the web.<p>Chances are that you will discover more than one fault. Emissions control systems are designed with a high degree of redundency, so an emissions failure is frequently the result of a few bad parts. <p>I believe that your car was originally fitted with converter PN 3531403. The recommended replacement part, 3531257-8, manufactered by Faurecia AB for Volvo, has a generic flange design and will not fit a 1991 240. This can be remedied by having some custom stainless steel welding done or crudely modfying the flange -- only to have it leak later. The original Volvo cat costs about $900. <p>Cheaper catalytic converters are available (even through Volvo which sells a replacement model for about $400), but don't perform as well. The really low-budget converters, which sell for around $250-300 simply don't last as long due to the fact that they're made from mild steel (rusts quickly) and contain less catalyst than higher quality units (do a poorer job of scrubbing the exhaust).<p>No matter which converter you buy, you'll probably need a new O2 sensor. This part is frequently damaged on removal (it's a real PITA to get out).<p>Hope this helps,<p>Paul<p><br>
 

·
Registered
Joined
·
212 Posts
Re: :confused: what to do in order to pass emissions test this year??? (RearWheelPaul)

I bow to Paul- he KNOWS about these things. <IMG NAME="icon" SRC="http://********************/smile/emthup.gif" BORDER="0">
 

·
Registered
Joined
·
80 Posts
Discussion Starter · #6 ·
Re: :confused: what to do in order to pass emissions test this year??? (brickboy240)

Wow, thanks alot Paul!<p>I'll start with the least expensive items and the easiest and work my way up to the converter and 02 sensor. I have had mechanics tell me "you probably need a converter" but the idea of just putting down money and tearing things out with little knowledge if they're truly faulty is unsettling.<p>I doubt I have a vacuum problem - my 240 idles beautifully and it gets good gas mileage. I change the oil and filter (Castrol Synthetic Blend and Bosch filter) regularly and put new spark plugs and a new Bosch dist. cap on it recently. I also replaced the air filter and looked the air intake over real good and saw no cracks or anything strange.<p>I have never cleaned the throttle body...is that difficult? That, along with an 02 sensor and possibly a cat might be my problem...I'll keep working on it.<p>Thanks!<p>- Brickboy240
 

·
Registered
Joined
·
109 Posts
I managed to pass smog even though my 240 didn't have a cat at the time. All of this was after doing the 'just bought it' flame trap/tuneup stuff. <p>I just had to adjust the timing a little and run some premium gas. I've since put a cat on, of course. 240s seem to be very clean-running cars, all things considered.
 
1 - 7 of 7 Posts
Top