I failed smog yesterday for NO at 15 mph. The smog guy said it could possibly be my thermostat because my temp gauge isn't working properly. My cel isn't on, I had just replaced my O2 sensor.

My readings @ 15 mph were: rpm 2445, %CO2 14.6, %O2 0.1, HC(ppm)16, CO% 0.02, NO(ppm) 580.

The readings for 25 mph were: rpm 2392, %CO2 14.6, %O2 0.1, HC(ppm)15, CO% 0.03, NO(ppm) 473.

I've look around online and from what i've read it could be this, but also says there could be a problem with the egr. I also have a cold air intake and don't know if it pulling to much air. Maybe a vacuum leak? Any ideas?

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1999 Ranger 3.0 V6 2wd

first off it's not your coolant lol
second off go see if you have any stored codes the computer might have

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also try ice o heet
I've heard of people failing smog and using that and then passing

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95 Ranger XLT 4x2 2.3 I4 5 speed 206,000 *dead*
96 Ranger XLT 4x4 4.0 V6 5 speed 173,000 *alive*
D35 front, 8.8 rear, 3.73 gears, limited slip rear diff

I checked and no codes stored, ill look into ice o heet. im thinking its a vacuum leak somewhere. im still going to replace the thermostat and check the hoses for leaks.

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1999 Ranger 3.0 V6 2wd

x2 on vac leak.

although if it a leak, it must be freakin tiny to not set a code. i'd lean more toward the EGR or a biased o2 sensor.

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2011 Ranger XL Extended cab, 2x4, 2.3 L Duratec, Automatic, Mis-colored Leer camper shell, Ultragauge, LED plate bulbs, DDM "cree" reverse lights. Staying as stock as possible

Does anyone know where the EGR gets its readings from? what tells the valve to open and close? is its temperature reading from the same source as the temp gauge in the dashboard?

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1999 Ranger 3.0 V6 2wd

ECM will manage opening/closing of the EGR valve. Whoever told you to look at the EGR system for problems gave you good advice, that's exactly where I'd have gone looking first. Make sure your EGR valve is able to open by applying vaccum to it and either seeing if you can feel rod movement on the valve itself or with(if) the engine running, see if it dies. Is there any indication that this vehicle is running hot or are you idling in line while you wait?

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000

egr valve works ive tested it with a vacuum and also cleaned it. i also replaced the egr solenoid, but that didnt change anything. my guess is that what ever is sending the signal to the egr isnt working properly. I have a lower NOx reading at higher mph. ive read it might be a faulty O2 sensor? My temp gauge also dosent work properly, it says im running colder than i should be, im going to repace the theromostat, temp sensor, and temp sending unit next. I think (but dont know) that the egr is getting signals that my engine is running colder than it actually is, so its not opening the valve as much as it should.

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What is the ECM?

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1999 Ranger 3.0 V6 2wd

Engine Control Module, another acronym for the 'puter and usually for ones that can't be flashed.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000