1996 850 smog failure high NOx

tomstir · Post by **tomstir** » 12 Jun 2009, 07:02

drsugg--the rest of the readings are......hc 23 at 15mph and 15 at 25mph and co% of .02 at 15mph and 25mph. Well below the limit.

Would excessive carbon deposits have any symptoms? I have read about the seafoam treatments...do you think that could help? Would you guys recomment doing that?

As far as I know the motor has never been apart and it's all original. That doesn't mean that it hasn't had some head warpage/milling...how could I check for that?

Should I check for timing marks being aligned? Is it possible that the belt has slipped? I though these were "interference" engines...how much slippage before valve/piston connection? Am I on borrowed time? I do plan on doing the timing belt by years end.

I did try and do some "preventative" maintanence and was reading about the fuel pumps going around 100k so I replaced mine last year....it's an aftermarket one...drives fine just a little louder than factory...is it possible that it's not pushing enough fuel? I figured there would be "driveability" issues if it was starving for fuel......I guess just a bit less would be enough to run lean/hot but not enough to feel. I also replaced the fuel filter when I did the pump.

Last year I had some hard starting issues for a few weeks and then my first and only cel.....it ended up being the mass which I replaced and cel never came back......I did have another cel come on about 2 months ago.....felt like something killed the engine right when it started...and produced a cel....started right back up and I disconnected the battery when I got home and cel never came back....could that be something? Would there be a code without a cel? What reading would I get if I disconnected the mass? I figure that as soon as the mass is disconnected the computer would send a cel and put the car into limp mode. Is that what you're suggesting? Then disconnect the battery to clear code and see if the car runs better? I guess I'm unsure by what you mean with "reading".

misha--thanks for the vacuum suggestions and directions...I will check on those later.

I really appreciate the help and directions...keep em coming

tomstir

drsugg · Post by **drsugg** » 12 Jun 2009, 08:55

Well, the rest of the readings look good but I'm still thinking something obvious has to be going on. Your nox readings are off the chart. I have a 97 850 with almost 200k, bone stock, original cat, passed smog in a flash. They have a lot of info on checking cam time on this site so checking should not be a problem.If it's the problem, it will be very obvious. Did you replace cat with a stock one or one of those weld in units? The weld in ones do come in two "flavors", obd 1 & obd 2. OBD 1 units do not scrub nox out like a obd 2 unit. I try not to use them. Vacuum leaks and fuel delivery problems usually will effect the other readings and may have noticeable drive-ability issues too. I could recommend a shop to you in the east bay if you need some pro help. Keep us posted!

tomstir · Post by **tomstir** » 12 Jun 2009, 16:04

drsugg--It was a weld on obdII unit. The nox was high even before the cat replacement....they did come down a bit after the cat replacement...so I think that is at least working. I'm leaning towards vacuum leak or bad o2 sensor.....your thoughts. Do you know of a way to test the o2 sensor while it's in the car? The only tests I have seen are where the sensor is removed and heated up with a torch and checked....that may be where I'm heading....I called a local repair shop and asked if they would test my o2 sensor and they would only do it if they removed it.....I couldn't remove it myself......at $90 an hour it was sounding very expensive....
My ego is taking a big hit right now!!!!

thanks for the suggestions

tomstir

Post by **vegasjetskier** » 12 Jun 2009, 16:24

Did you get it tested since you riveted the airbox in the cold position?

whoa · Post by **whoa** » 12 Jun 2009, 18:57

Tom, pulling the 02 sensor(s) takes just a minute or two for anyone who knows how the connectors work, so that's not going to add much to the labor.

Post by **Brucebo** » 12 Jun 2009, 20:41

tomstir wrote: Do you know of a way to test the o2 sensor while it's in the car? The only tests I have seen are where the sensor is removed and heated up with a torch and checked....that may be where I'm heading
tomstir

Do you have an OBDII scanner that displays "live data"? They're about $150. If so you can watch your O2S reading and it should swing from about <0.3V to >0.7V. This may be different for wideband sensors, but a '96 850 doesn't use these.

tomstir wrote: Brucebo---lowering the value by 75% might just get me to pass but I would like to fix the problem for good.....if I did what you suggested are there any negative side effects? I would hate to pass smog and continue to drive "as is" and make whatever problem I have worse.
tomstir

Long term, alcohol and "gasohol" are rumored to degrade some rubber materials in older vehicles, but a short term use isn't going to harm anything. "Methanol" (not ethanol) will also corrode aluminum over the long term, so don't use that. Methanol has two modes of action on aluminum. It dissolves the inert passivation layer that protects Al from the elements, and it also attacks Al metal directly.

-Bruce

tomstir · Post by **tomstir** » 13 Jun 2009, 19:32

Update..well I bit the bullet and went down to a smog/diagnostic place to have the car checked out....I told him what had been done and he checked it out...asked me a few question...looked at the previous test results and ran a few tests of his own....and said it should pass....put it on the rollers and it failed....he said that he put it through a practice run and it passed the first time and then failed the second time.....he then let me watch the graph (no) while he ran it again and it failed again 1825@15mph/3214@25mph. He told me it was the cat....I said I just replaced it two weeks ago and he said it was defective....he has personally pulled new cats out of the box and had them fail....more than one time.

I went to the muffler shop where I had the work done and the owner said that although that was rare it could happen....we walked to the other end of the complex where there was another smog shop and talked to them....they said it could happen. But weren't sure about it being the cat....but couldn't tell what they thought it was. The muffler shop doesn't have that cat in stock but can get it on Monday. He (muffler) shop did suggest misting water into the motor to clean the carbon off of the pistons....he said that Volvo's and Jeeps were notorious for the high no problems because of not having an egr.....sounds backwards but that has been his experience...I asked about Seafoam and he said he has always just used water.

I went back to the diagnostic place (forgot some paperwork) and told the mechanic about the muffler shop not having a cat in stock....he tried to find me one from their shop but couldn't....but he did "promise" that all my smog problems would go away with the correctly working cat. He even was going to bet me $500 that it would/will lower the no's to the 200 range.

Opinions please.....does any of this sound correct....seems to be such a hassle.....the mechanic did mention that there is a couple of years (1996-1998) that are refered as pre obd2 and they take their own specific cat. The cat that was installed is a---car sound obd2 c46006.

thanks guys
tomstir

Post by **vegasjetskier** » 13 Jun 2009, 19:44

Well since everyone's so sure it's the cat, have the original shop that put the current cat in put in a new one under warranty. That way you're not out anything.

tomstir · Post by **tomstir** » 14 Jun 2009, 05:24

The first smog place (test only) said when I went back for the retest after replacing the cat that it wasn't the cat....he is a test only so he couldn't diagnose the problem.....the test/repair/diagnose place (second place I took it to) said it was a bad cat and the new one must be defective...the third place (I just talked to) wasn't sure....they seemed more interested in getting my business and knocking down the other place I went to. The muffler shop said they will replace the cat for free...but didn't have a new one in stock...it will have to wait until Monday at the earliest....but he did suggest that I mist water into the motor to clean off the carbon. If the new cat doesn't pass I am still at the same place I started without any new info.....a "gross pulluter".

I'm tempted to try the Seafoam/water just to see....anyone have any experience with either method?

The mechanic did mention that there is a couple of years (1996-1998) that are refered as "pre obd2" and they take their own specific cat...anyone ever hear of this?

thanks
tomstir

tomstir · Post by **tomstir** » 16 Jun 2009, 01:52

Muffler shop didn't order cat....no progress.

Here's a new theory.....maybe a dirty fuel filter...causing less fuel to flow/lean condition.

any takers?