I failed my emissions test today. Any suggestions?

Here are the results in the form "current reading/standard (2004 reading, 2005 reading)". In 2004 the high speed test was at 2405 rpm and the standards were laxer:

High speed (25 mph / 2405 rpm)
HC (PPM): 138/148 (47, 122)
CO (%): .98/.94 (1.11, .72)
CO2 (%): 11.8 (11.1, 11.2)
O2 (%): 4.0 (5.6, 5.3)
NOx (ppm): 1499/1047
Dilution (%): 12.8 / >6 (12.21, 11.92)

Low speed (15 mph / 1468 rpm)
HC 240/152
CO .85/.86
CO2 12.1
O2 3.6
NOx 1613/1146
Dilution 12.9 / >6

[Edited to include 2005 high speed readings.]

 

Mark,

I recently went through the same thing, testing and failed O2 sensor was my problem. Your #'s are all over the board though compared to mine as I only failed due to NO. The others I am not to sure about. Was your engine/cat nice and hot when you ran it? It may make a difference.

High NOx is running lean and/or high exhaust temps.

Michael

 

Michael,

My engine was probably not heated up enough -- I went from a cold start to the inspection station 2 miles away. Before freaking out, I'll take the car for a serious drive (while avoiding revenooers) and take it to a different station.

Mark.

 

I don't know enough to tell you what is causing your excessive emission, but if you need new cats, I purchased a set for my '85 for about $250 - shipping in two days.

I needed to replace a test pipe to pass a safety inspection. If you are interested, I'll dig up the info for you.

I need to get an emissions test by April. Don't know if the cats pass emissions, but I'm going over one hurdle at a time.

 

John, IIRC cars over 20 years old are emissions exempt in MD. ...or is that only with historic registration?

Mark, having it warmed up will make a huge difference.

 

I had the car retested while hot. Here are the results:

High speed (25 mph / 2405 rpm)
HC (PPM): 145/148 (47, 122, 138)
CO (%): .88/.94 (1.11, .72, .98)
CO2 (%): 11.8 (11.1, 11.2, 10.5)
O2 (%): 6.3 (5.6, 5.3, 4.0)
NOx (ppm): 1594/1047 (1499 when cold)
Dilution (%): 11.38 / >6 (12.21, 11.92, 12.8)

Low speed (15 mph / 1468 rpm)
HC 182/152 (240 when cold)
CO .99/.86 (.85 when cold)
CO2: 11.0 (12.1 when cold)
O2: 5.4 (3.6 when cold)
NOx 1541/1146 (1613 when cold)
Dilution 11.99 / >6 (12.9 when cold)

So in the "high speed" test HC, CO2, O2, and NOx went up and CO and Dilution went down; in the low speed test, CO and O2 went up and HC, CO2, NOx, and Dilution went down.

Some additional notes:
In the last year, I haven't driven much -- 2500 miles, most of which was in the first six months.
I probably haven't done 500 miles in the last six months.
A couple of years ago I had a failed ECU cause a rich enough condition to dump fuel into the cats. I replaced the MAF and the ECU.
Idle is steady, but a couple of ticks high (800 or so instead of 675).

Any suggestions are welcome.

 

Hey Matt,

I thought there was a 20 year thing. I was going to look into it as the date got closer.

I did get an invitation for the emissions party shortly after I registered the car. I'm wondering if you get a 20 year waiver after the test? I remember about 20 years ago you could get a "pass" after a failure by just showing about $50 in receipts for plugs, wires, air filter, etc. Maybe they just want your $15 regardless if you pass or not. People's Republic of Montgomery County.

 

Mark,

Take a look at the following two threads:


https://rennlist.com/forums/showthre...ight=emissions

https://rennlist.com/forums/showthre...ight=emissions

Some have mentioned disconnecting a vacume line but I am not sure what years that pertains to. There is a lot of good reading in them. In VA you can take it back to the same shop for 15 days to re-take the test and it is no-charge.

Good luck! Let us know what happens.

Michael

 

Thanks, Michael. Those threads talk about high HC/low NOx (rich condition) and low HC/high NOx (lean condition). I still can't make any sense of high HC/high NOx.

I'm planning to test my O2 sensor, burn through this tank of gas, change my oil, fill up with fresh gas and take another run at it.

Any other suggestions?

 

I would say you are running rich. A rich engine will drive up h/c and nox. The most common would be the o-2 sensor, Ignition components, coolant temp too cold, exaust leak prior to 0-2 fooling sensor to a rich mode.

 

I will check the O2 sensor. Coolant temp is definitely not too cold. I went through ignition components about 5000 miles ago, but if the O2 gives the expected readings I'll do so again.

 

Did you disconnect the vacuum line to the auxiliary air pump change over valve? This is standard in Germany but nobody seems to know this in the US and is necessary according to Porsche. See Rog100 post about failed emissions.

 

Thanks, Schocki. I'll try it. Where in the Porsche literature is the emissions testing procedure?

 

Factory LH+EZK 87+ TEst Plan.

If your car has an air pump it needs to be disconnected (pull vacuum line).



Every gas station in Germany has a little booklet on how it's done. They all say that the secondary air injection has to be disonnected.

 

When you had the previous condition that dumped raw fuel into the cats, they may have overheated resulting in deactivation. If your O2 sensor is OK the cats may be the problem.