What can I do to pass CA smog?

[slamtry]

My 1995 convertible just failed the CA smog test. It failed a month ago so I put a bottle of Guaranteed to Pass into just over half a tank of gas and drove up the freeway for a couple of hundred miles. Then I put in a bottle of some stuff called Techron that is supposed to clean the injectors in with some more gas and drove another 300 miles. Then I changed the oil and filter and took it to get smogged again. It failed again. This time its numbers were better - it initially failed on Hydrocarbons at both 15 and 25 mph and on Nitrogen Oxide and O2 it failed at 15MPH. The second time it failed on Hydrocarbons and Nitrogen Oxide at 15MPH and passed on the rest.

I only drive the car about 1000 miles a year, which probably doesn't help. It had new plugs 4500 miles ago (okay it was 4 years) in a (successful) effort to get it through its 2019 smog test. On the other hand, it has not had a new O2 sensor for 50,000 miles (about 15 years ago). I know nothing about the specifics of smog tests. Would a new O2 sensor maybe get me under the limit for the HCs and the Nitrogen? The HCs were 198 with a maximum allowed of 85 and the NO was 980 with a legal max of 695.

Any help would be appreciated. I don't want to give up this car.

Dan

[Eric93se]

Yeah, gotta find all the vacuum leaks. Pre cat o2 sensor and a new set of ignition coils, $100 on eBay.

[JDStrickland]

High hydrocarbons (HC) come from unburned fuel. Your OBD 1 engine does not do a very good job of telling you that you have a lean condition, but if the fuel ratio is lean then you can have poor combustion, and this puts raw gasoline (unburned fuel) into the exhaust stream where the smog police will not be amused.

BEFORE you buy anything, you need to look at the underside of Item 3 in the diagram linked below. On my car, there were two ports where hoses similar to Item 12 plug in, the holes were cracked and the hoses fit very loose. The hoses were in good enough that they did not fall out, but they were loose enough that air was pulled in enough to give a lean misfire.

My HC was allowed to be 85, I scored 86. I also had numbers for two other categories -- I think they were CO and NOx, but I'm not certain on this point -- where the numbers were above the average but below the MAX allowed. I replaced Item 3 and my HC fell to about 4 (from the high 80s) and the two that were above the average fell to well below the averages for those categories. My fuel economy also improved, so win-win. You can get Item 3 from your auto parts store down the street from your house.

https://www.realoem.com/bmw/enUS/sho...diagId=13_1710

[E36 Em Tree]

Doing a lot of research on codes my car was throwing and i had come across purge valves being stuck open. From what ive read the job of that valve is to open during cruise and throw excess fuel vapor into the manifold BUT if its open when its not supposed to be (i.e during idle) then you may be running rich. I might be wrong because EVAP is a b**** but from what ive learned that was the main goal of EVAP and the purge valve. I think mine is stuck open.. and i know its common on other platforms too.

[lsynadinos]

For what it's worth, my '98 e36 was failing the hydrocarbons at 15mph. Turns out that it wasn't' hot enough when the test was being done. My mechanic said these cars have to be really hot when they're smog checked.

[E36 Em Tree]

I don't think I beat mine hard enough but also I think my fuel tank purge valve was stuck open making it run rich and I might throw some injectorncleaner in my tank. Gonna get it in the high revved range for a few days to clean out the tank and run through the cleaner and I'll report back

[slamtry]

I just looked at the hose mentioned by JDStrickland. That sounded like a dream: fix it all in one go with a $20 part or some electrical tape. Unfortunately, when I undid the hose clamps and pulled off the hose/boot, it all seemed to be solid without any cracking. Knew it was too good to be true. I might just throw in a new O2 sensor - it's been 50,000 miles. The only thing is - it is not throwing a code. Is it possible for the O2 sensor to be malfunctioning enough to throw my emissions over the limit without at the same time causing a code?

[E36 Em Tree]

Im in CA too so we can troubleshoot this together caused I failed as well but I already knew something would fail, just not sure what. I bought my M3 as-is and told seller I'd worry about smog.

Anyways HC can be due to running rich OR running lean (too much fuel to burn off, not enough o2 basically or wrong AFR). Anyways from my research it can be one or the other so its hard to troubleshoot it. Most likely its going to be a vacuum leak (make sure you have a BMW gas cap, make sure your EVAP lines are good). I'd say take it to a shop and have them smoke test the EVAP system for about an hour of book labor before spending money on o2 sensors (theyre about 175/each). Would be cheaper to see if they can smoke check it so you can rule out EVAP since thats the most common issue with HCs. I changed my fuel cap and I changed my fuel tank purge valve (or whatever you wanna call it). Im waiting to do my spark plugs after I run GTP and injector cleaner as well. Your injectors might also be bad/stuck open throwing in too much fuel as well. And then your o2 sensors could also be bad but i'd hold off and do that last since that'll probably be one of the most expensive and time consuming maintenance things to do.

As for Nox, that's usually from a bad catalytic convertor, from the research i've done. You might be able to run the car hard and get the cats to stay hot but when the shop does that required 3 min or whatever cool down and idle period it might slowly cool down. Another thing that I've read is that if your exhaust is putting out a percentage of o2 from the exhaust that the CC is not holding onto O2 efficiently enough, but haven't read if they was untrue or not. But my Nox was passing and my o2 was at 0% FWIW. I failed HC at 15 and 25 mph which makes mine a little easier to diagnose since I only failed one portion of the test.

A way to test your o2 sensors is from real time data log and code reader but not sure if obd1 supports that.

Anyways, Id check your gas cap, purge valve, evap lines, and smoke test. That should help HC.
Nox is the CC an usually the rear o2 sensors are there for that (but youd have to see the voltage and data being put out and if theyre responding)

Another thing that just came to mind is trying to use MAF cleaner on the sensor but I've heard mixed reviews on that and also the computer needs time to readjust AFR and whatever else the computer does.
Ill update you with what I'm doing next and if it works.

[JDStrickland]

I just looked at the hose mentioned by JDStrickland. That sounded like a dream: fix it all in one go with a $20 part or some electrical tape. Unfortunately, when I undid the hose clamps and pulled off the hose/boot, it all seemed to be solid without any cracking. Knew it was too good to be true. I might just throw in a new O2 sensor - it's been 50,000 miles. The only thing is - it is not throwing a code. Is it possible for the O2 sensor to be malfunctioning enough to throw my emissions over the limit without at the same time causing a code?

It's OBD 1, it can be lean and not throw a code. This is part of why they went to OBD 2. Poor combustion is the problem to solve. I had no idea that my car was not combusting well, I could hit 80 in the length of an on ramp and do 90 all day long. My car had more speed than my checkbook has money, so if it weren't for smog check, I would never have known that the car was not running well.

So the hoses in the bottom of the duct fit tightly? Mine were loose. Basically, Item 12 (and there is another) fits tightly into Item 3? The opposite end of the two hoses also need to fit tightly itso whatever they go to.

[E36 Em Tree]

I'd also look at plugs. Everyone swears by 1 prong NGH copper v plugs over 2 or 4 prong iridium and Plat plugs. I'm going cheap 1 prong coppers for my smog test this week to see how it goes.

I also found a little oil when I changed plugs so... I need to get it smogged before the leaking gets worse.

[E36 Em Tree]

Passed smog. Went from 144 HC to under 50 HC. Changed purge valve, 1 prong copper V NGK plugs, oil change.

[Eric93se]

Just know that copper plugs will wear down faster.

[E36 Em Tree]

Just know that copper plugs will wear down faster.

Only cost less than $2/plug. Was like 12.something shipped to my door with next day from autozone. And according to my SMOG results they make the car run cleaner. Worth it.

Took me less than 30 min to do and I'll probably make it routine every other 2nd or 3rd oil change

[gc325is]

The magic copper plugs How do they work NGK says

Most spark plugs contain a copper core for increased conductivity, improved heat control and improved resistance to fouling. "Copper spark plugs" is a term mistakenly used for a standard or traditional plug. Due to its soft nature and low melting point, using copper as an outer material would result in a plug that only lasted minutes. A standard spark plug uses a nickel-alloy outer material fused to a copper core. Some plugs also include a coating or pad of precious metals to extend plug life. As a general rule of thumb, all spark plugs utilize a copper core, but copper is not used as an electrode material.

Yet the common resistance of the spark plug is 5000 ohm too.

So Why are iridium and platinum tips not working? only the BMW e36 gods know.

[E36 Em Tree]

Shrug. I just go off what theyre called on the forums haha. Like guibo... not giubo haha.

But... I just call em 1 prongs to everyone else cause I can't tell the difference and I'm no plug guru which is why I read a million threads and found copper plugs run more effectively and efficiently for stock e36s. Anyone who says differently obviously doesn't have smog test results to back it up... probably.

1 prong ftw

[gc325is]

I put in a set of dual prong plugs. Had to remove them in 100 miles. I think the spark would travel along the porcelain carbon build up to the tip and made a smaller spark. The car started to misfired after that. The Single tip works best in my M50 OBD I A set of NGK reg copper core, V power or the G Power work fine.