Failed Emissions today

[Danster]

Before I post my results, I want to add that I was checking things out after the inspection and noticed I had a Code 51 showing up the scanmaster. I forgot to reset the ECM after unplugging the Direct Scan cable. This was while the car was running.

Mods are in my sig. I did also notice looking at the trans plus I had the setting set for Rich Idle. Don't know if this would affect anything.

Here are my results:

High Speed Emission Results (25 MPH)
RPM: 1965
--------------------Standard------Current Reading ---------Result
HC(PPM)--------------148----------------77----------------Pass
CO(%)----------------0.94---------------2.53--------------Fail
CO2(%)----------------------------------13.2
02(5)-------------------------------------0.1
NOx(ppm)-------------1047---------------23.7--------------Pass
Dilution(%)------------>6-----------------15.7


Low Speed Emission Results( 15 MPH)
RPM: 2071
--------------------Standard------Current Reading ---------Result
HC(PPM)--------------152----------------77----------------Pass
CO(%)----------------0.86---------------1.84--------------Fail
CO2(%)----------------------------------13.6
02(5)-------------------------------------0.1
NOx(ppm)-------------1146---------------320--------------Pass
Dilution(%)------------>6-----------------15.4

What do you guys think? I lowered my fuel pressure from 45 (Line off) to 39-40 lbs. Set the trans plus to a regular 3 inch setting from a Rich Idle setting. Reset the ECM and no more codes showing up. Anything else I should do/check before going back and trying again?

Dannyo

 

[Danster]

Ttt

 

[ijames]

The rich idle won't change anything - this shifts the idle blm up or down so you can get all the blms closer to each other but so long as the blm is in range (usually 90-150) the engine is actually running at the same air/fuel ratio. The error 51 is a bad eprom error. As far as I know when the ecm senses this error it flashes the check engine light very fast and goes into limp home/backup fuel and spark mode, where the emissions would be terrible with 50's. Since I have to assume the check engine light was off (or they wouldn't have tested you), this was just a stored code but there was no problem at the time the car was being tested so it also shouldn't have had any effect.

I hope Joe will chime in, but it looks to me like you may be a little rich. You can try dropping the fuel pressure another 5 psi but the ecm will correct for that as much as it can so it may not really do anything. Is your cat in good shape and was the engine and cat well warmed up for the test?

 

[gofstbuick]

As Carl stated, code 51 may initiate limp mode, in which case, the injectors will fire batch (or in pairs). You need to clear code 51 first. The emissions look a little rich, as co is up and NOx is down. If you lean it out, the CO will rise and so will the NOx, but you have a little wiggle room with NOx.

 

[JSAautomotive]

Your problem is you're running too rich (high CO). Either reduce the fuel pressure or hang a new LARGE cat on the car. Reducing the fuel pressure "might" get you into the ball park, but a new LARGE cat mostl likely will.

Depending on the prom you're running, it may want to try and compensate for reducing the fuel pressure. It might try and keep the target A/F ratio (hence BLM) where it wants it. Several have gotten "smog chips" to pass the emissions test. The reason I feel you have a combination problem is, your CO2 is low (low efficientcy). Which would usually couple with the higher 02 content. In other words, the cat isn't storing the oxygen it needs to reduce CO and HC effectively. I'm sure you've probably got one free retest. If you want to make sure the car will pass, reduce the fuel pressure and install the largest 3 way cat you can get your hands on. Don't listen to the muffler shop guys when they tell you the smallest one will support up to 5.9 liters. It's all about cross-sectional area of the substrate and how efficient the substrate of the cat is. The GM cats are VERY high quality. The aftermarket cats are "ok" by standard. It's a big problem in the non-dealer venue. Finding good quality cats that last and are as efficient as their factory counterparts has been a problem in the independant venue.

Good luck!!

John

Oh... and before I forget. The code 51 would bother me. It's usually either a checksum error with the prom or the ECM has a problem. If you have an aftermarket prom, I would contact the prom maker and see if he can burn you a new one. Just in case.

 

[Danster]

Went ahead and cleared the code. Turned the fuel pressure down to 30-40 PSI and set the Trans plus to Lean idle. Just in case, I added a little RXP to the tank.

The CO's came down to 22 at 25 MPH and 32 at 15 MPH. The NOx at 15 MPH came down to 120.

Used the same cat so I'm not sure if I've would have passed just clearing the code and lowering the fuel pressure or adding the RXP helped it more to pass?

Im just happy I passed and don't have to worry about it for 1 year.

Thanks again for everyones help!

Dannyo