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Hey everyone,

So I've had my Bronco for about 2 years now and have been continuously struggling to get the thing to pass smog. Originally, it was 3x emissions standards across the board (I'm in CA), but in the past year I've managed to bring it down using every tip/replacing every recommended part i could think of including but not limited to: replacing EGR valve and solenoid, running new vacuum lines, replacing plugs/wires, cap, rotor, O2 sensor, MAP sensor, rebuilt the injectors, and most recently replaced both front and rear cats.

I took it in for smog a week ago and passed emissions at both 15 and 25mph with flying colors, problem was that it failed evap. Brought it back today, exactly one week later, for a smoke test. Found the leak (Cracked seal on the gas tank) and fixed it, then retested: passed everything (with approximately the same numbers) except NO at 25mph. A week ago my NO readings were 15mph: 0 ppm, 25mph: 72 ppm. Today they came out at 15mph: 14 ppm, 25mph: 854 ppm.

I went to the same guy for the smog both times, and today he was nearly as baffled as I was.

My question is, what would cause the sudden spike? I understand that NO results from high combustion temperatures but why would it go up by 10x in one week (driven maybe 150 mi). I'm supposed to go back Monday for another go, is there anything I can do before then?

I've dropped nearly $2k and countless hours trying to pass smog, I'm incredibly frustrated and just at a loss at this point, so any tips/advice would be much appreciated.

Thanks,
Chase
 

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5,078 Posts
We need a LOT more info to give you useful, relevant answers. Start with "your Bronco". You didn't even mention which engine it has, but that's just the tip of the iceberg. Click this, read the whole caption (a few times if necessary), spend some time inspecting the truck, and then create a detailed signature with all the specs:
http://www.supermotors.net/registry/media/72354

Next, read this and follow the 1st link in the caption (the 2nd is probably dead by now):
http://www.supermotors.net/registry/media/858380

At this point, the only specific recommendation I have is pretty general: get the engine FULLY warmed-up before going to any smog test, and KEEP IT RUNNING while waiting for your turn.
 

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yo Chase,
As Steve advised; and;

Have you tried a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 ... ?

Visual Check
Battery is fully charged
1.Inspect the air cleaner and inlet ducting.
2.Check all engine vacuum hoses for damage, leaks, cracks, blockage, proper routing, etc.
3.Check EEC system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, proper routing, etc.
4.Check the Powertrain Control Module (PCM), sensors and actuators for physical damage; can use these two diagrams to locate ACT, TPS, EVP above EGR), Ignition Control Module (ICM) on distributor mounted years (Ford re-located the ICM from Distr side to driver side hood hinge area on inner fender liner in 92-96); to MAP;
Sensor Locations Diagram ECT, IAT and Water Temperature Gauge Sender; Sensor Locations Diagram ECT & Temp Gauge sender, PCV by Gacknar
see hot Links @
http://www.fullsizebronco.com/forum/showthread.php?t=328561
But I am sure you know where these are located!

5.Check the engine coolant for proper level and mixture.
6.Check the transmission fluid level and quality.
7.Make all necessary repairs before continuing
8. Check headlights

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears including Reverse.

Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch.

Turn off all accessories; radio, lights, A/C, heater, blower, fans, etc. (close driver's door)

Then turn off engine and wait 10 seconds.

Do KOEO test First

Post Code(s) here according to:
KOEO
&
KOER

High NOx
 

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First, fill in some details under your registered user name about yourself and your Bronco so we know what you have at a glance.....

On my last smog test, 2013 I went round and round trying to sweeten up the engine thinking that might help as it had in the past even though the engine only had about 12k to date BUT in the end I wound up replacing the CATS where the muffler shop indicated the forward CAT was probably an original which hadn't been replaced so once I got that done it passed with flying colors.....I 'll be preparing for another smog test this summer and we'll see what if anything I need to do different or not......:shrug

If you can show low income you can apply to the BAR Bureau of Automotive Repair where they will give you up to $500.00 for smog related repairs but you must take it to a "Star" approved smog & repair station and hand in the check/letter to them, you might be liable for up to 20% of the cost though but NBD......I wound up spending around $1200 in the end so that $500.00 would have paid for the cost of the CATS ($450.00) if I just started with replacing the CATS, lesson learned as they say, you can't expect different results if you keep doing the same thing over and over..:doh0715:

If you haven't already read "Sixlitre's" I done failed my smog test (tears) then put some time in as it' rather lengthy but very informative on how to get around the CA smognazibastards....

Good Luck ~ :thumbup
 

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I walked in with my registration, insurance and DL. She asked everything work, I said yep checked it before I came to see you. She said great and I bought a 2 year inspection. Don't miss CA at all.
 

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I envy you guys, Cali is a real PITA with this smog BS.....what a racket! :rofl:
 
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