Keeps Failing Emissions! - BMW Forum

Neil Paz · 10-16-2006, 02:45 PM

My `84 325e keeps failing the state (Virginia) emissions test.

I have replaced the cat and the oxy sensor (last week) and I just failed again.

The NO ppm levels are twice as high as they should be at 15mph and almost three times as high at 25mph!

The inspector said it could be a defective cat.

Before I go through the trouble and expense of putting on yet another cat, should I check something else?

Please help, if I get stopped again by the police I'm gonna get impounded.

nukeduster · 10-16-2006, 04:03 PM

combustion chamber temps are too high.

how are your oil/water temps? got an exhaust temp gauge by chance? what are your EGT's?

check the condition of your spark plugs. it'll tell you alot about the health inside of your engine by looking at them. take photos of them if you can ands post them here..

But worse comes to worse it could be a cat that simply isnt up to snuff of burning off all the excess NOx. Get a catco or magnaflow cat. Those are two brands I trust, other then OEM.

Neil Paz · 10-16-2006, 04:52 PM

Quote:

Originally Posted by nukeduster

combustion chamber temps are too high.

how are your oil/water temps? got an exhaust temp gauge by chance? what are your EGT's?

check the condition of your spark plugs. it'll tell you alot about the health inside of your engine by looking at them. take photos of them if you can ands post them here..

But worse comes to worse it could be a cat that simply isnt up to snuff of burning off all the excess NOx. Get a catco or magnaflow cat. Those are two brands I trust, other then OEM.

I only have an oil temp guage; it reads normal. The cat I got is a catco. Checked the spark plugs and they are worn down to nubs; that couldn't be it though could it? I'll replace them anyhow.

I'm thinking of getting a comprehensive diagnostic at Midas...they say that will give a better idea of what the NOx problem is.

nukeduster · 10-16-2006, 05:58 PM

Goto an emissions specialist where they are ase smog certified. standard mechanics often get it wrong when it comes to emissions diagnostics unless they specialize in smog.

Starmavin · 10-16-2006, 11:35 PM

Where are your HC levels at? A lean condition can also cause high NOx levels, cloged fuel filter or vacuum leaks in the manifold, intake boot leaks between the AFM and throttle body are very common, check for cracks in the flex segments. Make sure the oxy sensor is working and relatively new. An upgraded performance chip can also kick up NOx levels. Fill up with 93 octaine or use a name brand octane booster like 104+ next time you test, a higher octaine level will cut your NOx levels in half.

Being an ex-pa certified state inspection/emission tech I can tell you that midas will try to scare you into repairs, that's their job.

Change your plugs, bosch platinum or the +2 are good lasting plugs.

gotKRAUT · 10-17-2006, 12:31 AM

you are an ASE Master tech and suggesting platinum plugs in an E30?

MiguelACA · 10-17-2006, 12:51 AM

call me a noob, but whats wrong with platinum plugs?

gotKRAUT · 10-17-2006, 12:53 AM

nothing if the car is designed to run on them...if not they wont clean the electrode properly and they begin to foul, best bet is to stick with the bosch supers, or whatever your car came with...BMW knew what they were doing...

Starmavin · 10-17-2006, 05:34 PM

No car is "designed" to run on platinum plugs, that's like saying that synthetic oil is bad for your older car because the factory didn't design the motor for it, it's an upgrade in materials used. Even bmw advises the use of iridiums plugs over the stock platinum plugs in their newer cars, iridiums are not stock...

One basic rule applies to any motor: The better the spark the better the combustion. The only thing you have to keep in mind is the temperature the plug is designed to operate at, but you won't have to worry about this so long you use the plug that is listed for your application.

I have had bosch +2 in my car for a years and they have yet to "foul out", and I advise them to anyone with an m20. The +2 plugs work perfect and last 3 times as long as basic plugs.

gotKRAUT · 10-17-2006, 05:41 PM

lol man you have fun with that, i ran platinums in my last e30 and they were the correct "tempeture range" and the car ran AWESOME for about 3 months, then i started losing mileage and noticed it was running rougher, just by change i swapped out the plugs with the good ol stock supers and it ran mint for the following year, then i sold it...soo false you say? i say i will stick with my supers

MiguelACA · 10-17-2006, 06:33 PM

hmm, interesting, my car (95 325i) has the fancy ngk iridium doo hickies..they have about i dunno, 10k on em? more or less about a years worht of use, should i check them? or should they still be good?

Starmavin · 10-17-2006, 07:41 PM

Iridium plugs are good for 100K miles, however, some people change them out around 50k for good measure. Depending on how you drive and the type of mods you have on your car I'd say check them every 25k. But if you are 100% stock, check them when you see 50k on the clock.

BMWJNKY · 10-18-2006, 10:57 AM

All I'm going to say is that after working a BMW shop for more than 3 years now we have seen nothing but problems with plat. plugs in cars not designed to run them. The cars that have the most problems with the plat. plugs are the early cars with a classic style coil and even some of the early coil on plug cars had issues with them.

I highly recomend running the BOSCH WR9LS in your "e" cars and the W8LCR in your "i" car, and gap the plug at .032-.034". You can run the cheeper W8LCR in an "e" but I recomend changing the plugs once a year if you do. But at $0.99-$1.30 each for a W8LCR it isn't that big of a deal.

Neil Paz · 10-18-2006, 05:39 PM

Alright guys, settle down. I put platinum +4 plugs in yesterday and I can always switch them out to the Supers that were advised in the Bentley manual but that the parts shop didn't have on hand.

Now back to business...I got the car back from Midas with this info. The diagnostic said that the fuel mixture is lean. The mechanic cleaned out ($75) the debris and deposits from the core beneath the ECU and above the air filter. The emissions test he ran after that would almost pass the NOx limits at 15mph and the levels at 25mph dropped from three times as high to twice as high as the passing level (1296 ppm). He also said the new cat I put on was running 20-30% hotter at the inlet than at the outflow of the cat, which is the opposite of how a converter should heat up apparently. He gave me a recall order for the idle control unit that I took to BMW; they said it had been fixed almost 20 years ago.

Now I'm wondering if I have a bad ECU (located above the air filter), a bad Motronic Control Unit (located in the glove box), or a bad cat (mine COULD have been defective)?

Starmavin, during my initial test (pre-Midas) my HC was at 26 ppm out of a limit of 102 at 15mph and 44 ppm out of a limit of 185 at 25mph. I can get a new fuel filter and look into vacuum leaks in the manifold or intake boot leaks between the AFM and throttle body but I really need to know how to proceed next. The oxy sensor is new (last week) and I don't have a performance chip. If a tank of 93 octane and an octane booster like 104+ will work that well, it may get me through the test. Your thoughts?

Starmavin · 10-18-2006, 08:20 PM

ECU stands for (electronic control unit) AKA DME or computer and I'm not sure that you mean about it being above the air box, that is your AFM... I don't recommend +4 plugs they tend to run hotter than regular platinum’s. 93 with 104+ octane booster should cut your NOx roughly in half.

I want you to check two things after checking from the AFM inward for leaks, first would be the coolant temp sensor, if you have a Bentley it'll explain how to.

Then bridge the coolant temp switch, this is found in the thermostat housing with two blade push on connectors behind the thermo-time switch. This alters timing and idle functions depending on the coolant temp. When this switch goes bad it can cause your motor to do all kinds of weird and wondrous things.

When it works correctly it'll make your idle control module surge the motor's rpms when you first start it (the rmps flare to 1100 then fall) then fast idle the motor at 900 RPMs then when the motor gets a tad warmer (after about 3-4 min depending on how cold it is) it drops the idle back down to normal (around 700 RPMs) Use a cut end off of a blade connector to bridge it, this will make your idle control module work in basic mode and will stabilize the timing making sure that switch isn't causing any problems. Wrap it in electrical taps to make sure it doesn't ground. These were phased out in 88-89 models when idle contol was integrated into the DME. The BMW part number is 12631279720 and is $20.87 from realoem.com/bmw in the FUEL INJECTION SYSTEM section. Ask any local parts houses about it and they will just look at you funny.