Failed Emmissions Again! - BMW Forum

Butch525 · 02-09-2006, 05:04 PM

So, I take my 95 525i to the emmissions station, and because they were clueless on how to disengage the ATS, they wouldn't run it on the dyno and instead ran an idle test. Anyway, my HCs failed on the idle test by almost double.

Now, my mechanic thinks it's the cat (after replacing the 02) and wants to replace it with a $600 Walker cat. First, shouldn't a bad cat shoot an error code? And what about using an after market?

thanks in advance,
Butch

Torque · 02-09-2006, 08:41 PM

I hear that running the engine hard prior to the testing helps (at least with aftermarket chips; worth a try tho).

ATS? You mean ASC? How would having it on prevent the car from running on the dyno?

CBA · 02-10-2006, 12:07 AM

torque if the traction control is on when they run it on the dyno the ASC will kick in and lock up the rear wheels because the car will think it's losing control with the front wheels stationary.

you are right about running it hard for a little while.. usually cleans the hydrocarbons right out.

butch an after market cat will work but make sure that you dont have to go that far.. sometimes a simple oil change/air filter/plugs will do the trick.

keep us posted on what happens..

Butch525 · 02-10-2006, 08:33 AM

Yes, I did mean ASC, thanks. Anyway, I replaced the plugs and tried to run it very hot before the test and then very cold and had the same result. My mechanic says everything is running perfect pre-cat, he says he has it running at 99% efficiency. He's tested it on his own machine and says it passes up until the engine is running at normal temps, then it fails, thus his reasoning that it's the cat. Wouldn't the car pop a check engine if the cat isn't working properly?

ozarkmark · 02-10-2006, 09:57 AM

If the CAT is not operating properly, you should see a code. ON mine the code is: Catalytic converter below threshold effeciency cylinders 1-3.

I have 123,000 miles with the original cats and O2 sensors. My CE light came on about 30,000 miles ago.
Next week, I will be putting on a direct-fit OEM replacement.

What state do you live in??

Torque · 02-10-2006, 10:26 AM

Quote:

Originally Posted by CBA

torque if the traction control is on when they run it on the dyno the ASC will kick in and lock up the rear wheels because the car will think it's losing control with the front wheels stationary.

you are right about running it hard for a little while.. usually cleans the hydrocarbons right out.

butch an after market cat will work but make sure that you dont have to go that far.. sometimes a simple oil change/air filter/plugs will do the trick.

keep us posted on what happens..

Oh yeah, sorry about the ASC ... I don't have it on my car, so I wasn't really familiar with how it works.

BeelZibub · 02-14-2006, 10:41 AM

Unfortunaly the computers on these things aren't as good as they make out and don't always show a fault code when you'd think they should.

Mine for example failed it's MOT on emissions - fault codes showed a dodgy o2 sensor which I duely replaced. It worked and teh car passed, 1-0 to the computer.

At a service a couple of months later she was running much too rich but was not storing any fault codes at all - turned out the cat wanted replacing, and sure enough one custom stainless cat later the emissions were safely below the limit 1-1 then.

A few weeks later she started to idle roughly but was storing no fault codes at all. Emissions were up again, fuel pressure was as at factory, lockdown test was perfect (She's Nikasil lined too so that's a breath of fresh air!!!) so everything pointed at a vacuum leak. After a very exhaustive search a torn diaphragm in the vacuum system was found to be the culprit - one replacement diaphragm later and she again runs like a BMW should.

End of play Computer 1 Human experience 2

Sometimes you just have to bite the bullet and trust in man over machine - if your mechanic knows what he is doing and has manually removed every other option (like we had to) then maybe just he's on the right track?

ozarkmark · 02-15-2006, 12:57 PM

Glad it worked out for you.

BeelZibub · 02-17-2006, 05:59 PM

Quote:

Originally Posted by ozarkmark

Glad it worked out for you.

It did but after a lot of hard work and various shit mechanics - I estimate over 10 mechanics looked at it and not one could point out the problem without wanting to go on a "Spend & Eliminate" course, which usually entailed o2's, MAF and various other expensive components which had absolutely nothing to do with the problem - Basically if the computer doesn't tell them what the problem is they just work on a rather expensive "spend & eliminate" basis. This is mostly true of BMW techs who rely solely upon their stupid assed computers to tell them, what the problem is. They were the first to reccomend "changing the MAF, The o2's, the manifold gasket" all at expense to me of course (Over £2000) just to try and find the problem (and with those changes they would still have been far from the mark). In the end I employed a Fucking North African Immigrant to take her away for 3 days, find the problem and resolve it. 3 days later she was returned running like only a BMW could (problem was a torn diaphragm) and at a cost of only £300. - What more can I say???

ozarkmark · 02-17-2006, 09:57 PM

Quote:

Originally Posted by BeelZibub

It did but after a lot of hard work and various shit mechanics - I estimate over 10 mechanics looked at it and not one could point out the problem without wanting to go on a "Spend & Eliminate" course, which usually entailed o2's, MAF and various other expensive components which had absolutely nothing to do with the problem - Basically if the computer doesn't tell them what the problem is they just work on a rather expensive "spend & eliminate" basis. This is mostly true of BMW techs who rely solely upon their stupid assed computers to tell them, what the problem is. They were the first to reccomend "changing the MAF, The o2's, the manifold gasket" all at expense to me of course (Over £2000) just to try and find the problem (and with those changes they would still have been far from the mark). In the end I employed a Fucking North African Immigrant to take her away for 3 days, find the problem and resolve it. 3 days later she was returned running like only a BMW could (problem was a torn diaphragm) and at a cost of only £300. - What more can I say???

You have a good point about the BMW techs that totally rely on computer diagnostic codes. When my tranny was starting to slip last summer, I took it to the dealer to get a diagnosis. No codes = no problem as far as they were concerned and everything was "within spec". At least they didn't charge me for the visit.

The following week, I took it back the same dealer because the problem was easily reproduced. As I was taking the head tech for a short ride, sure enough the tranny started lurching and the engine revving very high with each gear change. The tech felt it and knew I was screwed. At that very moment, sure enough, the dreaded gear cog with a "!" light came on.

I don't think it is reasonable for the service techs to totally rely on computer codes when something is obviously amiss. First of all, a slipping tranny could be a safety issue.
I am just glad it is fixed now. Sorry you had so much trouble...

DIRTE30 · 08-10-2006, 09:03 PM

I'm not sure what year BMW went OBDII but if yours is a '95 I believe that it's OBDI. In which case you would not have a downstream O2 sensor. Without a downstream O2, there's no way for the computer to know if the cat is operating efficiently or not. I would say that your mechanic may have be on the right track with the bad cat thing! Idle is the time when it's hardest for the engine to process all the gases properly. By the way... all you have to do to shut off the ASC is pull the ABS fuse as this is what controlls the sys.