EFI Failed emissions test

[Pedestrian]

My 68 failed the Arizona emissions test
I have a good running 95 5.0 Mustang motor with Explorer intake and Thunderbird electronics. Last year I had a similar 5.0 with the same intake and electronics, the only real change I made is switching from stock exhaust manifolds to long tube headers. I installed the o2 sensors about 4-6" after the collector flange. Is it possible that my o2 sensors are too far down the exhaust stream?

 

[Bullitt94]

Do you have the air pump hooked up?

 

[Lmfp]

How can it fail inspection? Arent the 68's pre emissions?

 

[Bullitt94]

That's a good question, too.

 

[Lmfp]

I just dont see how they could fail it if it doesnt come with catalytic converters. I know my 73 is exempt. If they really feel like it they could get me for charcoal canister not being on it anymore but thats it.

 

[DirtDonk]

According to Ryan's site, that O2 location sounds like it's too far back, as you were suspecting. I don't remember the exact specs, but I think the sweet spot is somewhere between 9 and 12 inches from the last cylinder exhaust port opening. Hence shorty headers.
With your long-tubes, putting it up that high would mean it's in a single tube, which is not good either (though it might fool the computer in the right direction anyway?) and I'm not sure what other options you have.

I'm going to try to run long tubes too, but will custom make them with a chamber in the area I need to best mount the O2 bungs.

Good luck. What were the readings you got that failed you?

Paul

 

[scrapman1971]

How can it fail inspection? Arent the 68's pre emissions?

no. 1966 and older. which is stupid because even the people's republic of california is better than that

 

[ilovemaui]

Put the exhaust manifolds back on, pass emissions and then put the headers back on.

It looks like depending where you live in Az you can get an exemption by proving you've spent a certain amount of money trying to fix the issue.

 

[Lmfp]

Wow thats kinda jacked up..

 

[70_Steve]

the only real change I made is switching from stock exhaust manifolds to long tube headers. I installed the o2 sensors about 4-6" after the collector flange. Is it possible that my o2 sensors are too far down the exhaust stream?

I'm running long tubes with the O2 sensors about 4" past the collector flange, and it passes emissions with flying colors! As was asked, what's it failing?

 

[Pedestrian]

My son has the emissions sheet in his Bronco, I'll post up numbers tomorrow.

 

[blubuckaroo]

Post your test results, otherwise I'd have to guess.

 

[JDJ]

That sucks. Hope you get it fixed...

 

[Pedestrian]

Update with numbers
Loaded HC 215ppm Standard is 450ppm passed
Loaded CO .88% Standard is 5.0% passed

Idle HC 632ppm Standard is 450ppm FAIL
Idle CO .86% Standard is 5.0% Passed

Appears to be stupid lean across the board. In my experience with motorcycles this indicates a lean misfire at idle.
Fuel pressure is good, plugs look very lean but not detonation lean.
Like I said, this Bronco runs great at all RPM, I cleaned the MAF because I run a K&N but is appeared to be in good condition as well.
Checked for vacuum leaks, none found

 

[Broncobowsher]

Looks like a lean misfire to me as well.
Do you have the iming set to the 10 degrees? Too much initial advance can cause stuff like this as well.

As far as emissions testing, Maricopa county (phoenix) is the only place in the country that I know of that also makes motorcycles pass an emissions test as well.
Not the whole state of Arizona either, just Maricopa and Pima counties. And neighboring towns that have a lot of traffic into the tested counties. But the rest of the state is open game (for now).
I am now to the point I just make my projects pass even if they don't need to. Also makes them easier to sell. A bronco that can pass emissions in the Phoenix is worth considerably more then one that can't.

 

[Bullitt94]

Looks like a lean misfire to me as well.
Do you have the iming set to the 10 degrees? Too much initial advance can cause stuff like this as well.

If it's an idle misfire that's kinda what I was thinking, too. A popular mod for that engine is to bump the timing a few degrees to get more power from it. Like stated above, 10 degrees is stock for that engine.

 

[Pedestrian]

Haven't messed with it since last year when I installed a replacement motor. Pretty sure I set it a 12 degrees. Hard to believe 2 degrees would make that much difference.

 

[Bullitt94]

When I bumped the timing on my '94 GT it was at 8 from the factory and I went up to 12. My point is 2 degrees could actually be 4 degrees. Another thing to note is carbon buildup in these motors can cause detonation issues when the timing is bumped. May not hurt to run a can of Sea Foam in the tank, too.

 

[horsewpt69]

I don't wanna seem like I'm insulting your intelleligence, but are you running the H.O./5.8 firing order with your wires? That could be were your miss is coming from, rather than just timing? Again, just throwin possiblities out there. Hope you find the gremlin!

 

[Pedestrian]

When I bumped the timing on my '94 GT it was at 8 from the factory and I went up to 12. My point is 2 degrees could actually be 4 degrees. Another thing to note is carbon buildup in these motors can cause detonation issues when the timing is bumped. May not hurt to run a can of Sea Foam in the tank, too.

No carbon buildup, I had this motor completely apart for new bearings last year and a port and polish the year before. I have less than 6000 miles on it since teardown.
I will verify the timing.