Emisions

Motohead

SCCoA Member
I Have a 91 SC Recentlly redid the heads (Minor porting & blending stock Valves) ever since I have noticed lower vacume around 12-13 idel in gear and 16 in park. The car feals strong but it failed emmisions today. The NOx was high. I have herd high NOx emmisions can be caused by lean conditions ie. vacume leak which would go along with what im seing on the vacume guage.With that said I gotta ask whats the best way to look for vacume leaks? I listened all around and cant here any Maybe a can of WD-40 sprayed on the joints and watch the tailpipe for smoke?
 
Propane is the official test gas , you spray it at your connections and listen for the idle to change, fix that leak and start again. In a pinch, I use intake cleaner but I have not tried WD40, I don't know if its flamable enough. Good luck
 
I think WD40 contains silicon - not good for O2 sensors. Use something that is designed to clean the intake or a carb on the car. Those will not hurt the sensors and will be flamable

I don't think porting the heads should change your vaccum, a cam will.

Aaron
 
In the same boat

Hey
I recently did my headgaskets, and yesterday failed on high Nox 695vs450 allowable.
My car runs well and does not feel like it has any vacum leaks. The shop suggested I change the 02's, I don't usually do what somebody selling parts suggests - I am going to look at the output using an scope tonight and see what they are doing. It has been my experience that 02's usually fail, and result in running rich, I could be mistaken though.
Let me know if you solve your problem, and I will do likewise.
 
Did you change your oil before you got tested? Running rich usually kills the O2 sensors but they fail after about 50K miles anyway.
You can't really hear an air leak except maybe detonation/pinging under boost and thats why there is a procedure for tracking down these leaks. Good luck
 
Re: In the same boat

Peterdroy66 said:
Hey
I recently did my headgaskets, and yesterday failed on high Nox 695vs450 allowable.
My car runs well and does not feel like it has any vacum leaks. The shop suggested I change the 02's, I don't usually do what somebody selling parts suggests - I am going to look at the output using an scope tonight and see what they are doing. It has been my experience that 02's usually fail, and result in running rich, I could be mistaken though.
Let me know if you solve your problem, and I will do likewise.
Mine failed Nox last year.. Replaced my O2s anyway, but they didn't make much of a difference. If your car has a standard tranny, you very likely have an Exhaust Gas Recirculation (EGR) valve. That is what controls Nox.. If you have one, be sure its working properly and/or clean it. The auto trannys were rigged with a 3stage cat to control Nox.
If you want to know more about EGR, consult a Haynes or Chiltons manual or just do a web search.. there is a ton of stuff about it.

But back to the specifics... a lean condition is what causes excessive Nox emissions. In my case, I was getting a tiny amount of unmetered air in through the crankase breather tube which was loose which was pushing it over the limit. I found it accidently, reconnected it, ran some fuel injector cleaner through, replaced the O2s (just to be safe but it didn't matter) and it just squeeked by.. In my case, its likely that one of my cats has a weak 3rd stage.
Definitely check for vaccuum leaks. The car might be running just fine, but a tiny leak is just enough.
 
thanks, further notes

My car is an automatic, so no EGR.
Test Results:
........Limit..03'...01'.....99'
HC....62....16....16.....23

Nox..456..695..618..342

In January 2003, the guidelines for the test were tightened on us. where 618 passed in 2001, under the new fudge factor I no longer pass!!!!!!! I found out this was changing last December, and should have done the test then :-(

My NOx jumped between 1999, and 2001 - during this period, I installed a "gutted" larger style MAF. I might be able to reduce by changing back, but won't likely give me what I need.
I am going to look for intake/PVC leaks, and try to see if I can determine any difference in the 02 sensor signal if I create, then stop intake leaks, this will tell me if I am making much improvement.

My 1995, with very low miles - that HAS EGR - read ZERO NOx.

From reading the "Ford Fuel Injection and Electronic Engine Control" book, I don't believe our cars have a 3 way catalytic; there is not air pump, to add air to the cats in our car, which looks as if it is the only visual difference.

Also according to this manual,Nox increases with spark advance above 20 degrees BTDC. Maybe pulling the octane plug and knocking the timing back might gain something as well, what do you think?

I really don't think 02's are going to make any improvement in this situation. Maybe I should swap CAT pipes with my 95....

Furthermore, I cleaned the injectors when I did the head gaskets.

Do you think "blow by" would have any impact on N0x? I suspect it would only show in HC's???


If I could get it to run a bit richer, I have lots of HC room to spare, maybe this is how I can pull the combustion temperature down a bit hmmmmm
 
Thats a good idea with the octain plug I'll try that, as far as cats I have new hi flow 2.5" I believe there single stage (No air inlet tubes) and an auto (no EGR). I got a propain torch removed the head and attached some hose started the car and spent close to an hour (Used up the whole tank) with no results but my vacume gague still reads about 13 idel in gear around 800 rpm and 16 in park. Where is the low octain plug located? and is there a way to retard the timing without a ECC tuner?
 
Octane Plug

The octane plug is located in the pass side corner rear of the engine bay, near the EEC connector.
I have been trying to use up my high octane gas this weekend, still have 1/8th of a tank.
Hopefully tomorrow I will retest on regular:
Octane plug pulled,
180 Thermostat,
Red line water wetter,
Regular gas,
replaced my "gutted"MAF with 55mm Stock,
whish me luck, when I get results I will post.
Further, I am going to try to get them to do it not so fully warmed up. I had lots of room to spare on HC's, so maybe it was just too hot during their test.
Later
 
Generaly the higher octane is also a cleaner gasoline and burns much cleaner the the lower grade gasoline, according to my inspection station.
 
From what im getting pulling the octain plug will retard the timing possiblly lowering cylnder temp and lowering NOx emmisions. Im headed to the inspection station now`
 
YeaHOO!! it pased Here is what I did, with the help of you guys I decided to pull the octaine plug and add alcohol with 3/8 of a tank of 93 octaine I put in 2 quarts of rubbing alcholl from walgreens (Its on sale 2 for 3.00!!). My nox emmisions fell to non existant from 4.6 to .29 Thanks a bunch to everyone who poasted I got another one but I'll start a new thread for that.
 
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