HELP! 1990 300CE failed Texas emission test
 

Results for high speed/low speed:

HC (PPM) 454/445 (Standard = 140/144)

NOx (ppm) 3512/3189 (Standard 984/1077)

According to the info sheet possible reasons are:

- O2 sensor
- EGR valve or hose
- Ignition timing and system (advanced timing and ignition components are some of the most common problems)
- Pirimary feedback sensor failure including MAP/MAF, TPS, RPM and CTS sensors.
- Vacuum lines (deterioration of vacuum lines, inlet manifold seats, and become more prevalent causes with age).
- Catalytic converter. (edit: replaced Jan 09, so it can be excluded)

My car has no OBDII how can I narrow down the cause? Is there a pre-OBD device with push buttons somewhere? and why there is no CEL at such bad numbers?

Before the inspection I had fuel system cleaned, I changed spark plugs and coolant.

I've got 14 days to get re-inspected; I'd appreciate your inputs since the spectrum of causes is to wide for me.

When was the last time the O2 sensor has been replaced? Are the spark plugs the correct NON resistor plugs? When was the last time a full on tune up was given to the car (air filter, cap, rotor)?

I bought the car 2 weeks ago on impulse. Last tune up according to records 01/22/09 with Cat replacement. O2 sensor replaced in 2004. Can it fail again?

I am not sure about spark plugs, bought them (Bosch 7927) from auto zone and checked on Bosch website that they fit my car.

Distributor cap & rotor R&R 2005; air filter just replaced last week after purchase.

What troubles me is that on my 1996 E320 at least I can plug an OBDII scanner in and get some clues, but pre-1992 cars don't have that nice feature.

Okay, the plugs you bought are the copper cored super plus. Not the best, but they're the right ones at the very least. Cap and rotor are due in for replacement right about now if they were last replaced 5 years ago. What kind of "tune up" did the car get on 1/22/09 if they didn't replace the cap and rotor? They can certainly effect your emissions performance by transmitting a weaker spark than necessary for super efficient combustion. Air filter is a good start. You can rule out your cat converter being the issue here, as if it's a new replacement, then it's highly unlikely it would fail so soon. O2 sensor's usually last around 50k miles or so. In my opinion, with it's age in mind, I'd replace it. They don't get replaced in such intervals that they should be skimped over on maintenance. When they fail, they either do it gracefully, or they die.

What I am suggesting you do, since you've just purchased the car, give the car a FULL tune up. This will let YOU establish a baseline on the car that you will know and not a baseline established by 5 year old records. From what I've read and experienced, all that's required to return acceptable emissions, is a full on tune up. A real tune up, not just the plugs.

Just an FYI, there really are only three types of *acceptable* plugs for your car. They're the following:

NGK - BP6EFS
Denso - T20EP-U
Bosch - F8DC4

The Bosch plugs you have are technically the same as the F8DC4 plugs. Aside from the fact that the ones you bought have a Yttrium electrode.

Thanks, after purchase I did the following R&R mostly by myself:

- spark plugs change with Bosch (7927) FR8DC Super Plus with the Yttrium electrode (a Y).
- coolant flush
- air filter replacement, oil change has been done by PO on 01/13/10
- brake bleeding
- fuel system cleaning at Walmart Tire & Lube

The car runs great, engine is strong although a bit loud.

It is now too late but could a PPI have revealed emission issues?

Can I get some diagnosis on emission problems with a code scanner (still to be built as in http://www.peachparts.com/shopforum/attachment.php?attachmentid=37619&d=1162392878 ) at the 16-pin connector near the battery?

PPI covers the car's mechanics. Suspension, rust, brakes and all that. I've yet to see a mechanic that does emission testing as part of a PPI. As for the code scanner, I don't know.

What's your fuel mileage? And what do you mean the engine is loud? These M104's are rather quiet with little to absolutely no valve train noises. Usually with poor emissions comes poor fuel mileage and what not. The engine is running great because these engines love fuel and heat.

my fuel mileage after the first 300 miles is 20 mpg mixed 50% highway 50% city and I think it is doing OK.

As to the engine being loud, it is subjective and compared to my 1996 E320 which I find a bit more quiet with almost same odometer stand (169K).

About PPI and emission I think like you that it is not recognizable.

OK, can anybody confirm this theory? Before the state inspection I put a bottle Guaranteed-to-Pass (G2P) to a full tank then drove 240 miles, the fuel gauge was at about 1/4 mark. I filled up then went to inspection, that means some of the G2P was still in the tank. Some people think that could mess up the emission. Any comments?

Should I drive until the tank is empty without doing anything then re-take the emission test? but if the theory does not hold and I fail the test again, what is the fine for expired state inspection ticker?

If the engine sounds loud, you could have an exhaust leak. A leak can confuse the O2 sensor. You may also have a bad cat, even if it was recently replaced.
It's too late to do it now, but you should have made passing inspection a part of the sale.

I checked and did not find any exaust leak, the engine gets louder at 70+ mph.

You will laugh at me but before the purchase as I saw the inspection sticker 1-0 my mind must have played a trick on me and I thought it were until October, how stupid.

Was it a real cold day? Did they do it on the dyno?

On my cars, I ussually change the oil right before hand. I run them hard and get them very hot.. try to be the first one there in the morning. You can simply fail if the cat isn't up to temp.
Is it running rich? Maybe the temp sensor is out of range- you can measure it and compare with spec.
Is the new cat a factory cat or some cheapo aftermarket?

M

I would agree that the cat needs to be as hot as possible, so be sure to run your car at freeway speed for a half an hour before the test. Also, replacement cats are often of lousy quality and will not last nearly as long as the originals, but yours should be ok after one year.

You might want to get a new rotor, and could get by with carefully cleaning the cap, if you don't want to spend a lot of $ on a cap.

Also, a very common problem is plugged EGR tube in the back where it is very hard to get to. The actual EGR valve is usually very bullet proof. There is a great thread on this forum about cleaning this tube out with out taking it totally out of the car. By using a speedometer cable attached to an electic drill, you feed about three feet slowing into the tube from the EGR valve side of the tube to "rotor rooter" it clean. Search this forum for a very good description of this procedure.

Here's the link I was referring to: http://www.continentalimports.com/ser_ic20134.html

I took the inspection at 1pm after driving 35miles. So the engine was hot when I arrived. However I had to wait 30min, maybe the engine was getting cold again.

The cat was replaced to a total cost of $680.- part and labor and I heard that factory cat was over $1,400 in part alone, so it was most likely aftermarket stuff.

My PO wouldn't have wanted to spend that much on 20 year old car.
Car running rich or lean? I don't know, what do the numbers say?

Thanks, I am still trying to open up the pipe at the EGR valve to clean. At intake manifold it is very very hard to access, the link says same thing.

What were the designers thinking when putting the egr far back close to the fire wall while in the front there is so much room there, Why can't they put it on the front exhaust manifold? either they wanted to save half a foot of egr pipe or it is their way to make money in maintenance :mad: :mad:.