2003 Mach 1 failed emissions, high nox - help?

ShawnaLane

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Aug 15, 2020
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I bought a 2003 Mach 1 with 13k mikes on it. It had a supercharger put on it by previous owner who worked for Ford. I had it emissions tested yesterday, and it failed due to high nox. I’m wondering what the possibilities for cause could be. I don’t pretend to know anything about engines. My husband put regular unleaded in it, and we’re still on that tank, so my first question is, would running through it and getting it back on premium make a difference? The limit is 1.xx, and it tested at 5.xx. Just trying to prepare myself for what I might be spending at the shop if something simple like switching fuel doesn’t work.
 
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Nightfire

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A nox failure rarely has anything to do with emissions (cars made after 1996 aren't tested for emission, they are tested for default codes. Does the car have the ses warning light on? A nox failure means that a combustion chamber (could only be 1 or all 8) is experiencing temps exceeding 2500F. There are 3 leading factors that will cause excessive cylinder heat.

1. Your AFR is WAY too lean. Fuel also acts to cool cylinder temps. If you're running lean means that your not getting enough fuel.
2. Overheating. What does your temp gauge usually show? I there is a problem with cooling then it can cause the excessive cylinder temps
3. EGR failure.

There is something that is of particular concern to me. First of all, it is beyond rare to find a Mach with only 13K miles on it. Second, we need a LOT more info about the car being "previously" supercharged. Only 13K miles and you're having this problem? Things just aren't adding up.....
 

ShawnaLane

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Aug 15, 2020
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I don’t know what AFR or EGR mean. I know how to drive cars, and that’s about the extent of my knowledge, unfortunately.

I don’t ever notice the heat gauge being abnormally high, but I will pay more attention to that.

You seem to suggest that it may have more than 13k mikes on it. How would I know if that’s the case? The engine is impeccably clean, so I didn’t see a reason for that to be suspect. What more do you need to know about it being previously supercharged (and why is “previously” in quotations?)?

I have an appointment with a mechanic on Tuesday to have it diagnosed. Hoping it’s something simple. Off to educate myself on AFR and EGR.
 

Mustang5L5

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My husband put regular unleaded in it, and we’re still on that tank, so my first question is, would running through it and getting it back on premium make a difference?

FYI, 2003-2004 Mach 1's require 91 octane or higher. You shouldn't really be putting 87 octane in.


Couple questions. You claim the car was previously modded? IS it returned to stock now? What does the car have for exhaust? Does it have catalytic converters on it?

High NOX is usually a few things

1: Engine running very lean
2: defective (or non-existent) cat converters
3: failed EGR
4: high mileage engine with lots of carbon buildup (not the case here)

It can also be from other reasons such as an exhaust leak, bad O2 sensors, vac leaks etc.

In order to properly answer this, we need to know what sort of mods the car has and what state of tune the car is in?
 

ShawnaLane

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Aug 15, 2020
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FYI, 2003-2004 Mach 1's require 91 octane or higher. You shouldn't really be putting 87 octane in.


Couple questions. You claim the car was previously modded? IS it returned to stock now? What does the car have for exhaust? Does it have catalytic converters on it?

High NOX is usually a few things

1: Engine running very lean
2: defective (or non-existent) cat converters
3: failed EGR
4: high mileage engine with lots of carbon buildup (not the case here)

It can also be from other reasons such as an exhaust leak, bad O2 sensors, vac leaks etc.

In order to properly answer this, we need to know what sort of mods the car has and what state of tune the car is in?

Yeah, I know about the fuel. My husband was trying to be nice. He knows better now too. The listing for the car said everything was stock besides the supercharger. I do not know enough about cars to verify that. I’ll have to wait and see what the mechanic says tomorrow. I didn’t realize there could be so many things causing the issue. Sorry for not being able to provide more info.
 

7991LXnSHO

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The combustion chambers’ temperatures will not show on the temperature gauge. That gauge measures the engine coolant temp.
EGR is Exhaust Gas Recirculation, and although counterintuitive, adding exhaust to the incoming air and fuel lowers the combustion temperatures. It does not add it at full throttle.
 

nickyb

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This is exactly why a non car person should always have a mechanic check car BEFORE you buy it. I really hope the seller did not sell you a headache. My fingers will be crossed for you,let us know what happens.
 

ShawnaLane

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This is exactly why a non car person should always have a mechanic check car BEFORE you buy it. I really hope the seller did not sell you a headache. My fingers will be crossed for you,let us know what happens.
Well, turns out the blower was installed, but it still has stock fuel injectors and pump, and the back O2 sensors were removed and system tampered with to avoid check engine light. It's a $3000 migraine. I trusted the dealership, and considering the low mileage, I thought it was safe to assume that it had been babied. I was sorely mistaken. Hard lesson learned. Stuck with a car I can't afford to get legal.
 

nickyb

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Well, turns out the blower was installed, but it still has stock fuel injectors and pump, and the back O2 sensors were removed and system tampered with to avoid check engine light. It's a $3000 migraine. I trusted the dealership, and considering the low mileage, I thought it was safe to assume that it had been babied. I was sorely mistaken. Hard lesson learned. Stuck with a car I can't afford to get legal.
Try and get some free legal advice. I hate with a passion stealerships,yes they even Rob there friends so I put them as low as a pregnant ant.
 

ShawnaLane

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Aug 15, 2020
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Try and get some free legal advice. I hate with a passion stealerships,yes they even Rob there friends so I put them as low as a pregnant ant.
The shop who has my car is helping me find a lawyer to get some help. Hopefully there is some recourse.
 
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Mustang5L5

Put lubricant all over the balls
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Do you want the blower on this car?

I would think you can pull it all off, put the car back to stock and get it to pass and sell the blower and make out "ok".
 

nickyb

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Good luck, I hope you can keep your stang and enjoy her for many years to come.
 

ShawnaLane

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Do you want the blower on this car?

I would think you can pull it all off, put the car back to stock and get it to pass and sell the blower and make out "ok".
I mean, who WOULDN'T want the supercharmer (assuming it's all done correctly)?! I do want it, but it's not completely necessary. To have it taken off and the O2 sensors replaced will be half the cost of having it fixed. So that's still about $1500 that I don't have.
 

7991LXnSHO

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I wonder what affects coolant temps.....
If the coolant system is functioning properly, it will absorb and dissipate heat even with variations in the combustion chamber temps. Neitherr it nor oil temp will not provide an accurate reading for this purpose. An EGT (Exhaust Gas Temp) probe will be a much more accurate measure of combustion temperatures.
 

Nightfire

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If the coolant system is functioning properly, it will absorb and dissipate heat even with variations in the combustion chamber temps. Neitherr it nor oil temp will not provide an accurate reading for this purpose. An EGT (Exhaust Gas Temp) probe will be a much more accurate measure of combustion temperatures.

Yes, Im sure a properly running coolant system could adequately hand cylinder temps of 2500+. Standard cylinder operating temps hover around 1200.

/sarcasm
 

7991LXnSHO

wanna catch the space herp
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@Nightfire do not try to take what I said out of context to the extreme just to make a great impression on the new member. The press does that all the time to folks and it is not necessary. While coolant temp readings are affected, the coolant temp gauge is not able to tell what cause of high NOx is, and certainly not what cylinders are tuning that hot. And while a bad cooling system can be the cause of it, but I hope the OP would notice that gauge or warning light.

@ShawnaLane Here is an article that might be more helpful.
 
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