Passing emissions with high CO

[HAAANK]

A few weeks ago I went to get emissions done here in Ohio and I failed due to high CO. This past Saturday I went back but just before I arrived I retarded the timing and passed with flying colors.

I was stoked and wanted to share the success for posterity.

 

[greentruck]

Guess I'm blessed by my ignorance and lack of experience with emissions testing in our neck of the woods. I would've thought low CO was a good thing, the less, the better? But maybe it indicates another issue that's not directly measured?

 

[SmokingRocks]

A few weeks ago I went to get emissions done here in Ohio and I failed due to low CO. This past Saturday I went back but just before I arrived I retarded the timing and passed with flying colors.

I was stoked and wanted to share the success for posterity.

What style of test did they use?

Idle sniffer or treadmill driving loop simulation?

 

[Rifleman]

That's a new one on me, never heard of failing an emissions test for having a CO value BELOW the emissions test fail point. Running the Federal IM240 test on a 1994 Land Cruiser, to fail that test you would have to have a test reading OVER 1.20% CO, any reading less then 1.20% CO, you'd pass. The whole point of doing vehicle emissions testing, is to make sure your vehicle is AT, or BELOW those Federally mandated emissions testing limits.

 

[HAAANK]

I meant high...edited title and op.

Guess I'm blessed by my ignorance and lack of experience with emissions testing in our neck of the woods. I would've thought low CO was a good thing, the less, the better? But maybe it indicates another issue that's not directly measured?

What style of test did they use?

Idle sniffer or treadmill driving loop simulation?

That's a new one on me, never heard of failing an emissions test for having a CO value BELOW the emissions test fail point. Running the Federal IM240 test on a 1994 Land Cruiser, to fail that test you would have to have a test reading OVER 1.20% CO, any reading less then 1.20% CO, you'd pass. The whole point of doing vehicle emissions testing, is to make sure your vehicle is AT, or BELOW those Federally mandated emissions testing limits.

 

[HAAANK]

What style of test did they use?

Idle sniffer or treadmill driving loop simulation?

Idle sniffer

 

[Tedward]

Only one set of rollers so fulltime 4wheel drive gets the idle sniffer. Unless they plug it in, but my 95 comes up in there system as obdI.

So what was your timing at when it failed and what did you change it to for the win?

 

[greentruck]

I meant high...edited title and op.

No problem, HAAANK. The older I get, the easier it is to get things backwards. Takes a man to correct things publicly.

Now if I just had some good advice about your high CO readings...

 

[HAAANK]

Only one set of rollers so fulltime 4wheel drive gets the idle sniffer. Unless they plug it in, but my 95 comes up in there system as obdI.

So what was your timing at when it failed and what did you change it to for the win?

Last I set it, ~2 years ago, it was at factory spec. When I went in for the echeck I just turned it back almost all the way. Didn’t take a reading unfortunately. I had marked the line before adjustment so I just took it back to original position.

 

[HAAANK]

No problem, HAAANK. The older I get, the easier it is to get things backwards. Takes a man to correct things publicly.

Now if I just had some good advice about your high CO readings...

Thanks! I make enough mistakes that I’m used to it by now, ha ha.

Per Ohio law, this is that last time this cruiser needs the echeck. I’m going to delete all the smog and egr stuff once and for all.

 

[Rifleman]

Now if I just had some good advice about your high CO readings...

The original poster retarded his timing to correct his CO readings.

Most emissions control manuals will tell you that retarding your timing will have no effect on tailpipe CO readings.

I've found that's not always the case, retarding your timing can cause the exhaust temps in your exhaust system to run hotter.

That higher exhaust temp can act like an extra CAT in your exhaust system, helping to burn off excess CO before it makes it's way out of your tail pipe.

One more thing to remember, and this is very important, emission testing adjustments are always a balancing act.

Making changes to correct one value that's caused you to fail your test, Be it a change to help correct for CO, can effect other emission testing values.


So if you make a change to your timing, higher, or lower engine idle speed, or running to rich, or to lean of a air fuel mixture can cause your other emission testing values (CO, HC, NOx, and O2) to fall outside of what would be a passing amount.

 

[Starlord]

Excess CO results from a rich condition. If it's at idle it's likely a O2 sensor, air filter limiting air(or other air intake obstruction) , bad MAF sensor, or possibly a faulty engine coolant temp sensor.

 

[inkpot]

Only one set of rollers so fulltime 4wheel drive gets the idle sniffer. Unless they plug it in, but my 95 comes up in there system as OBD I.

The Feds did not require OBD II until 1996, so most, if not all, states consider the 1995 as an OBD I rig even though it has a full complement of OBD II systems on board. Kinda sucks?

 

[Tedward]

Yup. What really sucks is I went a long time thinking it was obdI.
Plugged it in at several autozone or whatevers and got nothing. Thought it had all the parts but missing some detail of obdII.
Finally realized it IS obdII