Failing Emissions Test (E28)

Over the past several years I've had to replace my aftermarket catalytic converter 2 or 3 times. Just recently, I brought my E28 to a state inspection center and unfortunately I failed the emissions test. The inspector indicated that I should bring my car in for a tune up and that should resolve my problem but I have a funny feeling that I will have to change the catalytic again. Is there a resolution to this? I hate to purchase a OEM catalytic especially when the part itself is worth more then the vehicle and then you through the labor cost on top of that. Any thoughts or recommendations to pass the NJ state emissions test? Thanks for the feedback.

Well when you changed your Cat, did you change the O2 Sensor? If the problem is the Cat, MAGNAFLOW sells a direct OEM quality replacement which is
only about $300 a far cry less than a BMW German OEM replacement! Other than that, change your oil unless that has already been done, and
at your next tank, Fill up with 91 grade petrol.
Soo Oil, 02 sensor, New Magnaflow OEM cat, 91 Grade petrol, and your MAF sensor could cause a problem.........Are you having any idle issues?

If you keep changing your CAT, you're going about it the wrong way. You need to determine what's the malfunction in the engine, fuel system, ignition, etc. Start with the condition of the spark plugs, wires, cap, rotor, coil, etc. When was the O2 sensor replaced? Compression test would be next. The idle air control valve should be cleaned and inspected for proper operation. Lots of things can cause a car to fail. The emissions tests usually give you some specific numeric results. What were those? Last resort, move to Illinois. They don't test cars more than 12 tears old.

Need the experts to weigh in on the pros and cons on replacing my exhaust system (catalytic and rear muffler) for e28 535i. My mechanic tells me that for my vehicle all aftermarket catalytic converters and rear mufflers are worthless, they are too small for the vehicle, resulting in high idling, HC and CO readings. Is this correct? I'd hate to spend close to $4k for an entirely new exhaust system if there is a comparable alternative. Please provide names and websites for those comparable alternatives. Thanks for the response.

Originally Posted by dlchice

Need the experts to weigh in on the pros and cons on replacing my exhaust system (catalytic and rear muffler) for e28 535i. My mechanic tells me that for my vehicle all aftermarket catalytic converters and rear mufflers are worthless, they are too small for the vehicle, resulting in high idling, HC and CO readings. Is this correct? I'd hate to spend close to $4k for an entirely new exhaust system if there is a comparable alternative. Please provide names and websites for those comparable alternatives. Thanks for the response.

There recently was a thread about somebody putting together a nice inexpensive aftermarket exhaust. It was posted about two or three months back including undercar pictures of the finished product. If you want good quality, you can't go wrong with Bavarian Autosport. They have the converter for about $410 and the muffler assembly about $280. I have a number of friends that used their stuff with no problems.

I've got the Magnaflow direct fit cat and an Ireland Engineering Performance exhaust. My state inspection is due this month, but I don't anticpate any issues.

I spent $270 on the cat and $450 on the cat-back. I was also able to recycle the OEM cat, got paid $150 for that. I had to repace that because I had several leaks ahead of the O2 sensor.