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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 02-16-2013, 09:56 PM
ali.allo ali.allo is offline
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BMW 96 328i fails at Smog test High No @ 15 mph

Hi,

I am trying to pass the smog test for my bmw 96 328i which has 116 200 miles. It passed smog with flying color when I bought it 10 months ago.

First time I tried the engine was warm but only for 10 minutes and those where my number, I barely pass the test (orange marking).

My mechanic told me to pressure clean the injectors and change the fuel filter ($230 for that) and that would work since I am on a low budget...

I passed the test again after warming up the car for 1 hour on the highway (4k rpms on the 3 gear, auto transmission...), and I failed WORSE ! (yellow marking)

I filled up the tank as well with Chevron 91 octane premium gas

what would be your advise ?
I plan to change the air filter and the 6 spark plugs tomorrow


thanks guys
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Last edited by ali.allo; 02-18-2013 at 10:28 AM.
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  #2  
Old 02-17-2013, 12:00 AM
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southpark11235 southpark11235 is offline
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Your best bet would be to run some Sea Foam though the gas tank and intake. Then check for vacuum leaks.
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  #3  
Old 02-18-2013, 10:27 AM
ali.allo ali.allo is offline
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hey, thanks for the answer.

I just changed the air filter and the 6 plugs with those NGK BKR6E
I am running a complete full with CRC Guaranteed to Pass and I'll go check again !

Do you know how to check any vaccum leaks ?
any other clue ?

Thanks!
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  #4  
Old 02-18-2013, 12:06 PM
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drivinfaster drivinfaster is offline
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i agree with a top engine clean, such as seafoam, to help with reducing emissions. also check your fan clutch, egr system, and repair as necessary.

oxides of nitrogen (NOx) is an indicator of high combustion temps, but is also its highest when the co and hc are at their lowest.

co2 and free o2 are in good order, though, so it does not appear at this time that a cat will be needed.




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Old 02-18-2013, 12:12 PM
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southpark11235 southpark11235 is offline
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Quote:
Originally Posted by ali.allo View Post
hey, thanks for the answer.

I just changed the air filter and the 6 plugs with those NGK BKR6E
I am running a complete full with CRC Guaranteed to Pass and I'll go check again !

Do you know how to check any vaccum leaks ?
any other clue ?

Thanks!
This sould help http://forums.bimmerforums.com/forum....php?t=1083796
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Alex//1999 323is - power e46 M3 seats, style 43 rims, 328 exhaust, Z3 rack, Bilstein PSS coilovers

We got about ten minutes before this entire county is up in flames. If you want to live, youd better step on the gas! Oh wait is this a Tesla? Sh!t! Well, step on the prissy peddle, we're going to die! Cartman
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  #6  
Old 02-18-2013, 01:52 PM
ali.allo ali.allo is offline
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Thanks!

I've read over and over on Internet that retarding timing should help, do you know if it is easily doable on this model of car?

I've seen the fan clutch rotating quite normally, not sure for what I need to check.

Regarding high combustion temp, do you know if there is any octane/fuel that could have a lower combustion temp point?
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  #7  
Old 02-18-2013, 02:37 PM
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hornhospital hornhospital is offline
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Timing isn't externally changeable. It's set by the ECU.
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  #8  
Old 02-18-2013, 02:39 PM
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Quote:
Originally Posted by ali.allo View Post
Thanks!

I've read over and over on Internet that retarding timing should help, do you know if it is easily doable on this model of car?
no. timing is controlled by the pcm
I've seen the fan clutch rotating quite normally, not sure for what I need to check.
google 'how to check a fan clutch'
Regarding high combustion temp, do you know if there is any octane/fuel that could have a lower combustion temp point?
higher octane will reduce spark knock, but not so much combustion temps.
knock sensors would be inputs for pinging/spark knock, but before going that route, i would do the seafoam service. just make sure that you road blast it for a lot and do it at normal operating temps or it won't be as thorough as possible.




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  #9  
Old 02-18-2013, 03:27 PM
ali.allo ali.allo is offline
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I already put a bottle of CRC Guaranteed to Pass in the tank and my mechanic shop injected a direct concentrate cleaner through the injectors.
Would Seafoam be efficient here (or it is like repeating 3 times the same thing?)
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  #10  
Old 02-18-2013, 03:37 PM
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not a big fan of the crc gtp products, but a cleaner through the injectors will be enough to start with. see how that does and go from there.

they all (sorta) do the same thing. some are better than others. depending upon what system the shop used, it may be ok, or it may be great. even with a better product, if it isn;t done properly it will not be as effective as it could be.

i have even done top engine clean/decarbon services with a strigger spray bottle and water. it's all in knowing what you are doing...



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  #11  
Old 02-18-2013, 05:03 PM
ali.allo ali.allo is offline
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thank you for the advise, I'll keep updated!
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  #12  
Old 02-18-2013, 05:31 PM
granlund granlund is offline
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If you haven't rebuilt the VANOS yet, I believe this could have something to do with the high NOx. These BMW engines do not have external EGR (to reduce NOx) like most other cars. Instead the intake cam is phased to adjust overlap for internal EGR. If the VANOS is not advancing the intake cam (due to worn out seals) to create cam overlap and internal EGR, ignition will be retarded due to pinging and you will simultaneously have elevated NOx and HC (from the incomplete combustion).

Last edited by granlund; 02-21-2013 at 12:44 PM.
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  #13  
Old 02-19-2013, 06:33 PM
ali.allo ali.allo is offline
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aaannnd it failed again
rainy day, about 50F outside,
I've done air filter, fuel injectors clean up, NGK spark plugs, fuel filter, checked leaks and a bottle of Guarented to pass !
I run the car for about 15 minutes in traffic (so slowy) since NOx is high temp and the car idled for 10 minutes before the test

check out the picture, the technician ran it at 1818 mph and this time there is some O2 (because of the weather ?)

since I want to sell the car is there any magic recipe to pass those 50 ppm ?!

granlund, I don't think I have a rebuilt Vanos but I really don't want to spend a lot here
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  #14  
Old 02-19-2013, 06:45 PM
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i would think it would be because the cat wasn't lit?? that's a *huge* difference in both free o2 and co2 there.

did you take the car for a road blast after the injector cleaning?? or did you just dump that gtp additive in the tank??




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Old 02-19-2013, 07:41 PM
ali.allo ali.allo is offline
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I took the car for a blast sure thing after the cleaning, put the 3rd gear up to 4k rpms and when I dropped the additives, I drove it crazy as well to empty the tank
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Old 02-19-2013, 10:45 PM
ali.allo ali.allo is offline
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btw do you think testing the car at 1800 rpm instead of 1400/1500 could have effect the NOx to go over the limit?

I am thinking in putting some Ethanol in the fuel. What do you think?
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Old 02-19-2013, 10:51 PM
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HakenTT HakenTT is offline
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NOX means combustion temperature is too hot. May be do to carbon deposits on top of the pistons.

There should not be any smog test for 1996 anyway, but be the california thing then
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Old 02-19-2013, 11:30 PM
ali.allo ali.allo is offline
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I ran a complete bottle of CRC Guaranteed to pass and injectors cleaning for the carbon deposits, I doubt it would be that.

I understood NOx occurs from lean mix meaning there is too much oxygen (??). I am considering putting back the old dusty air filter to reduce the air/fuel ratio.
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Old 02-20-2013, 03:03 AM
granlund granlund is offline
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NOx occurs because the combustion temperature is too hot. The amount of formed NOx increases sharply at stoichiometric ratio and stays high going into lean. Adding recirculated exhaust gas lowers the combustion temperature because it is inert. Changing the air filter will not affect anything. What you need to do is either retard ignition or increase valve overlap.
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Old 02-20-2013, 04:29 PM
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^neither of which are able to be done on this vehicle....


since it is obd2, check your egr system is not restricted.

since you have done a fuel system service (done at a shop, if i understood correctly), *and* added a bottle of crap (gtp), i don't think that carbon buildup would be an issue.




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Old 02-20-2013, 07:37 PM
granlund granlund is offline
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^neither of which are able to be done on this vehicle....


since it is obd2, check your egr system is not restricted.
Valve overlap is changed with the VANOS - this is the (internal) EGR system.

Ignition timing is retarded on pinging when the overlap is too small. This is done automatically by the ECU.
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Old 02-20-2013, 08:17 PM
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Originally Posted by granlund View Post
NOx occurs because the combustion temperature is too hot. The amount of formed NOx increases sharply at stoichiometric ratio and stays high going into lean. Adding recirculated exhaust gas lowers the combustion temperature because it is inert. Changing the air filter will not affect anything. What you need to do is either retard ignition or increase valve overlap.
the bolded makes it sound as if it is something *he* could do on his own, and it is not....that is the point i was trying to make.

Quote:
Originally Posted by granlund View Post
Valve overlap is changed with the VANOS - this is the (internal) EGR system.

Ignition timing is retarded on pinging when the overlap is too small. This is done automatically by the ECU.
vanos doesn't kick in until 3000rpm, if i understand the operation, and is is for the intake cam only. dual vanos manages to adjust exhaust valve timing, which will affect NOx. the e36 did not get dual vanos as i recall.

i'm not saying he couldn't have some sort of issue with the vanos unit, but if that were the case, then i would suspect that this would also increas the emissions across the range of rpm, andnot just the lower rpm.



op, is this a manual?? if the vehicle were in the wrong gear, that could affect the rpm and speed needed for optimum performance and emissions. just throwing that out there, as the drop in co2 and increse in o2 is *waaaaaayyyy* out of proportion.....just throwing that out there....



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Old 02-21-2013, 06:42 AM
granlund granlund is offline
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vanos doesn't kick in until 3000rpm, if i understand the operation, and is is for the intake cam only. dual vanos manages to adjust exhaust valve timing, which will affect NOx. the e36 did not get dual vanos as i recall.
The VANOS system has the intake cam retarded for no overlap at idle. It can advance the intake cam 12 degrees for overlap causing internal EGR. However, there is no feedback and CEL code if the single-VANOS does not partially, or fully advance unlike the dual-VANOS engines.

If the VANOS piston seal is worn, it can partially advance (without error code) and allow less EGR. Since combustion speed is slowed down with EGR, ignition timing is advanced when the VANOS is told to advance the intake cam. However, this ignition advance takes place regardless of whether the intake cam actually advances or not. If you have too much ignition advance (without EGR), pinging will occur (causing NOx), timing will be retarded because pinging is detected by the knock sensors and there will be a loss in performance and increase in HC from incomplete combustion.

With intermediate VANOS seal wear, one may not be able to feel the loss in performance as with the full wear. However, NOx and HC will increase when the engine moves in/out of pinging.
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Old 02-21-2013, 08:33 AM
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i disagree that advanced timing causes NOx and pinging.

pinging, or spark knock, is what occurs when there are 2 sources of heat igniting the air/fuel mix in the cylinder.

the one source of heat is the spark plug, and most often times the 2nd source is from hot spots on the piston face (usually deposits of carbon). this collision is what makes the 'marbles in a can' sound, and is *not* the piston slapping arund the cylinder wall.

think about it. there isn't enough clearance in the cylinder to do this, and if there were, there would be more issues than 'pinging'...


also, ignition needs to be advanced as the rpm increases since the piston speed increases, but not the rate of combustion. the rate of combustion is static and will not change.


now, whether or not a leaky vanos seal is the possible culprit, i cannot say. i would figure that there would be additional related factors that would point to this as a possible cause, such as poor fuel economy and noise. neither of these were stated.

since this is the interwebz, it's very difficult, if not impossible, to diagnose everything that could be possible causes. the best way (of course) is to have the car present and assess for yourself.

the second failure, however, screams of something not being done correctly. i base this on the co2 and o2 readings. there should be no reason for them to drop off the way they did compared tothe original test uunless there is somethggn amiss. however, since i was not there, i can only speculate.




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Old 02-21-2013, 11:34 AM
granlund granlund is offline
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Ignition advance is well known to cause pinging and elevated NOx and HC. If the ignition is advanced too much, the resulting pressure increase from the ongoing compression will interfere with the flame front combustion (and pressure increase) initiated by the spark plug. The result is auto-ignition of the yet unignited air-fuel mixture causing compression waves bouncing back and forth in the cylinder that we hear as "marbles in a can". These vibrations are picked up by the knock sensors and the ECU appropriately retards ignition.

The rate of combustion changes with engine speed because it is affected by the turbulence/swirl/tumble in the cylinder that increases with engine speed. Or were you referring to rate of combustion in non-dimensional crank-degrees instead of dimensional milliseconds?

Going back to the OP's emission protocols - the partial passes are marginal. Even though it passes at 25 mph, the NOx and HC are still elevated far above the average values which would be an average of new and old cars with functioning emissions systems.
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