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OMF
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Discussion Starter #1
So I took the Bronc-oh for emission and safety inspectiond today.
It failed emissions with high CO, the max is 5% and it was around 8% at idle and high rpm.
The Holley pro-jection system has an O2 sensor that it can monitor and adjust fuel accordingly.
I still have to have a bung welded in for that,
but I am also wondering if it that doesn't cut it will a catalyst take care of the high CO?
 

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There's a 99% probability that getting the O2 sensor installed will take care of your problem. If not, yes, a new catalytic converter will knock those CO levels right down. HOWEVER, that is a short term solution as the formerly new cat is quickly degraged by this process, and the next time you go in for emissions testing you'll be right back where you were, or worse.
If you were going to go that route, you may want to put the cat in, take the test, and pull it off again to keep it from being ruined.

Best bet: get that O2 sensor in there and do it right. I had the bung welded into my exhaust for $20 by a local shop. When you do it, make sure that they do it on the upper side of the pipe (anywhere on the upper half of the diameter). If an O2 sensor is installed below the mid point of the pipe, too much moisture will condense on it and severly shorten the life of the sensor. Most shops know to do this, doesn't hurt to remind them.
Good luck.
 

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you need to post the rest of the test to see whats going on. it can be burning a little to lean.
 

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Unless California rigs are different, 78 Broncos did NOT have cats. Check your filler neck, if it is OE, and large opening, your Bronco did not have a cat convertor.
 

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OMF
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Discussion Starter #5
Unless California rigs are different, 78 Broncos did NOT have cats. Check your filler neck, if it is OE, and large opening, your Bronco did not have a cat convertor.
My rig did not come with a Cat, I know that for sure, the engine has the non catalyst sticker on it.

As far as other readings go:
**** CO2 ** O2 ** HC ** CO
Idle: 9.77% .28% 379 PPM 8.2%
2500 9.47% .20% 264 PPM 8.7%

Any help would be awesome, I am going to have the O2 sensor installed after I get the transmission and transfercase finished.
 

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whats the limits for each?

no NOX?
 

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OMF
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Discussion Starter #7
Nope, no NOX..

Let's see the HC max is 1200 PPM, mine was 379 & 264
The CO max is 5%, mine was 8.2% & 8.7%

CO2 and O2 have no limitations, duh!
 

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I am going to guess and say becuz there is no O2, thats why it failed. I beleive once the o2 is put in your HC and CO will both drop
 

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OMF
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Discussion Starter #9
This in my guess as well. I am curious to see how it runs once it goes in.

I am going to do a six litre tune up as well, just in case it is a cylinder not firing properly, it doesn't miss so I think this is unlikely.

I have never had a fail due to CO, only HC in the past so this seems odd to me.
 

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hey raleigh im thinking that u need to weld that bung in there so the projection can work. im thinking the trucks running lean cause it cant get a good reading causing ur CO or carbon monoxide to go up. id say install the bung and i think with the projection u have to run it a while for it to get all adjusted im not 100% on that but id say give it a good running befor u take it back. ur HC are low they should be 600-800 ppm if i remember correctlly which is another indicator of it running lean
 

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OMF
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Discussion Starter #11
So the consensus is to install the O2 sensor, drive it for a week or so then take it back in.

I have to take it back within 30 days for the retest I don't have to pay for.
 

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hey raleigh im thinking that u need to weld that bung in there so the projection can work. im thinking the trucks running lean cause it cant get a good reading causing ur CO or carbon monoxide to go up. id say install the bung and i think with the projection u have to run it a while for it to get all adjusted im not 100% on that but id say give it a good running befor u take it back. ur HC are low they should be 600-800 ppm if i remember correctlly which is another indicator of it running lean


it should not make it run lean. it should run rich unless it is setup way wrong for the engine. Lean melts pistons.



pull a few plugs and see what they look like.
 

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OMF
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Discussion Starter #13
Pulled the plugs today, not too bad but on the rich side. Installed some new Motorcraft plugs and Accel wires.

I believe the major issue here is that the temperature sensor is not sending correct voltage to the ECU.
It seems to be in "choke" mode all of the time, I found this out cause I had the O2 sensor installed and that should make the ECU adjustments null.
Well even at normal operating temps I can still adjust the ECU and it affects the fuel, that should not happen with this set up.

I will be installing a separate temp sensor for the ECU in the morning.

On a side note I have a bit of a "tick" coming from the passenger side bank so I guess I will pull the valve cover and see if something is loose, maybe a rocker?
 

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OMF
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Discussion Starter #14
Well she passed with flying colors!

Less than 1% CO and 50 PPM HC.

What a relief!
 
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