Author Topic: Failed Emissions :( (Read 7204 times)

juliea · « **on:** November 19, 2009, 08:09:25 PM »

I've been having lots of problems with my E30 M42 recently....latest one being a failed emissions test.

My HC emissions were high at idle (enough to fail) and at cruise (not enough to fail). My CO emissions were fine.

It idles a bit roughly, but runs well when I give it gas.

We recently had the car apart to fix an exhaust valve. I'm wondering if we might have an air leak somewhere. Would appreciate advice on how to troubleshoot the issue...I'd like to get my car back on the road after it's been laid up for the past couple of weeks.

quinn11m20 · « **Reply #1 on:** November 19, 2009, 09:09:19 PM »

One where are you from?
Its important because of the Clean Air Act. Parts of the US are segmented and have certain guidelines. Some, like California are more strict, I am from Florida and we don't have any.

There is a product made by the CRC company. The name on the box is "Guarenteed to Pass". They usually sell this product in Auto Zone, Advanced Auto, Pep Boys and so on.
I recommend you try it first. When I lived in Ca, I used it on my 85 318i and passed just so I could register the car and then 2 days later report to Fort Hood, TX and a few days after that changing my license and registration. It help me quickly.
CRC makes a lot of other products as well.
You know this could be down to something like changing your air filter and make sure all your hoses are tight.
Non of us can pin point what is exactly wrong with your car, it takes a little troubleshooting on your part. And as a bonus you get to know your car. It will grow on you very much. I have had mine 91 318is since 97 when I was still at Fort Hood.

jgraves · « **Reply #2 on:** November 19, 2009, 09:44:59 PM »

Mine failed the first time I took her for the emmissions test in New Jersey two years ago. Everyone kept telling me it was the catalyic converter. All I did was get some gumout to clean the old engine oil from the previous owner, changed the spark plugs, wires, and oil. Then I took her back the next day and she passed. I don't know if you'll be that lucky, but that's what I did. This year I know what I have to fix, the rear muffler.

Ramblin MAn · « **Reply #3 on:** November 20, 2009, 09:34:13 AM »

What was your idle speed during that part of the test? How many miles you have on the motor? What kind of oil are you running?

If you are getting a lot of blow by and oil going into the throttle body, that is just more "goo" that is being combusted and/or clogging things up in the throttle body and everywhere else. Might not be enough to cause smoking but it may be enough to skew tests and coat O2 sensors etc.

DesktopDave · « **Reply #4 on:** November 20, 2009, 09:45:33 AM »

Vac leaks are raelly common on these cars. A sticky idle control valve is common too. Check both out, let us know if you need tips or pointers. We like to help out, and we've seen all the common problems.

Trust me, the more you work on it the more you'll get to like the car.

juliea · « **Reply #5 on:** November 22, 2009, 01:41:57 AM »

I've definitely gotten my hands dirty with this car, and I do like it very much

I'm pretty dedicated to getting it run...

We've replaced the plugs, redone the exhaust valves, and don't seem to be losing oil. I'm thinking that a vacuum leak or the ICV might be an issue, since the idle is rough. The car hasn't idled smoothly since we've put the engine back together. Can you guys provide me with some tips to find leaks and/or troubleshoot the ICV?

Thanks for the help!

juliea · « **Reply #6 on:** November 22, 2009, 12:42:16 PM »

A few other questions - how do I tell if my engine is misfiring? The idle speed varies and it doesn't sound like it's running perfectly smooth - but I'm not sure if it's rough enough to constitute a misfire.

bmwman91 · « **Reply #7 on:** November 22, 2009, 10:27:07 PM »

Chances are that it is the catalytic converter. When I failed a couple years ago, I replaced cracked hoses & tuned everything up & still failed. After I put in a new cat, I passed with emissions that were like 1000% below the limit, and well below the averages from all the other cars getting tested.

juliea · « **Reply #8 on:** November 23, 2009, 04:13:25 PM »

Is there any way to test my catalytic converter to know if its bad before replacing?

bmwman91 · « **Reply #9 on:** November 24, 2009, 11:47:06 AM »

Although I am being a little sarcastic, I would say that failing SMOG is a guarantee that the cat is bad. Unless the motor is missing a vacuum line or has a completely broken spark plug, you should be able to pass.

The one other thing it MIGHT be is the O2 sensor. Generally though, if that is dead enough to fail you in SMOG then you should either get a check engine light, or like 20mpg. What's your mileage? That's the main way to determine if it is control system related, or the cat.

1991 E30 M42 · « **Reply #10 on:** November 24, 2009, 02:23:19 PM »

If the cat restricted is you could also get poor mileage. I would replace the cat either way, its almost 20 years old, it has got to be restricting exhaust flow to some point. You can pick up a 2.25" magnaflow cat on ebay for around $100 and you should be able to get a local exhaust shop to install it for somewhere around $50.

juliea · « **Reply #11 on:** November 26, 2009, 03:25:36 PM »

To give some more background and answer some of the previous questions:
- I'm testing in WA state
- MPG seems normal
- Engine started idling roughly only after we took it apart to replace the exhaust valve
- Air filter looks fine
- Air flow sensor, TPS work
- ICV buzzing
- New plugs
- New ignition wires
- Engine compression is good

Ok, I did some research and digging around about the cat...and I'm not sure that's my problem, despite it being one of the most "obvious" causes. If my cat were bad, wouldn't my HC and CO emissions be high at both idle and cruise? Here's the way I'm thinking about it - feel free to poke holes in my logic if it doesn't make sense.

The cat has two functions - converting CO to CO2 and converting unburnt HC's to CO2 and water. My CO emissions were under the required limits, for both idle and cruise. The ONLY test that I failed on was HC's at idle. I think that if the cat were bad, I'd have high results on both HC and CO, at both idle and cruise.

I compared my results to last year's - and found that my HC's were higher at both idle and cruise. My CO emissions were exactly the same for idle, but twice as high at cruise (though both were well under the required limits). My CO+CO2 emissions were the same as last year. My O2 emissions were half what they were last year at cruise, and 13 times higher at idle.

I think the O2 results are telling me that my engine runs rich at cruise (too little 02), and lean at idle (too much O2). Not yet sure where the problem could be, but thinking potentially O2 sensor, exhaust leak upstream of sensor, vacuum leak, injectors, potentially leaky exhaust valve (though I hope not, since we've just done the repair...). Again, I'm also giving a higher consideration to things that would have changed since we've done the repair, since I didn't have the rough idle prior to that.

So....if you'e gotten to here, thanks for reading. Any further suggestions for things to check & how to check them? Planning to dig in more next weekend. Thanks for the help!

juliea · « **Reply #12 on:** November 26, 2009, 03:53:26 PM »

Oh, a few other answers to previous questions:

- I'm running 20/50 oil, changed 2 wks ago
- I don't know exactly how many miles the engine has on it - it's a used motor; we just had it apart to replace a burned exhaust valve, and also replaced timing chain guides, front crankshaft seal; pistons were a bit loose, but not too loose; it compression tests fine now.
- Idle speed fluctuated between 8 and 900 RPM, but averaged 810, according to test results

Greg Mierz Mtechnic · « **Reply #13 on:** December 08, 2009, 11:55:40 PM »

Just a little clarification of the issues. I did the head job for Julia. Also rerouted the hoses back to stock from a kluged arrangement on the icv and crankcase hoses. We pulled the plugs which looked good, not wet or carbonized. The coils were tested with a large gap plug and 3 of 4 looked the same and one was weaker in appearance. The motor was tested for vacuum leaks again and passed. The ICV was cleaned again and seems to work. The O2 sensor seems to pass but appears rather old and crusty. The plug were fresh when the valve job was done a couple of weeks ago and the plug wires replaced a week later. Compression is good and even.The fuel injectors were a bit dirty looking and I'm wondering if one leaks down a little. It is frustrating for Julia and puzzling for me. Any ideas would be welcomed

Ramblin MAn · « **Reply #14 on:** December 10, 2009, 08:58:19 AM »

You think you could be a tooth off on one of the cams? What about the run like crap wire? That didn't get hooked up did it? The wire that tells the computer it's using the CO adjustable AFM and not the US version?