While jumping right into this, I would like to start off by saying that I’ve been chasing an ongoing issue with my manual 2003 Mach 1 for months and I’m reaching the point where I’m ready to give up on diagnosing it myself and take it to a shop.

For some insight, the car currently has approximately 117,600 miles, a K&N intake, stock manifolds and H-pipe, and Borla ATAK mufflers.

The original recurring code was P0172 (System Too Rich Bank 1). It came back roughly once per month in March, April, May and July. Then in August, instead of P0172, I received P0420 (Catalyst Efficiency Below Threshold Bank 1) twice within five days and only 164 miles. The car is my daily and mainly drive it with highway miles considering a 60 mile round-trip commute, so this is pretty concerning for me.

I’ll attach the freeze-frame reports separately so everyone can see the fuel trims, speeds, RPM, load and fuel-pressure data for themselves.

The main symptoms have been:

- Uneven and slightly shaky idle

- Car sometimes rocks at idle almost like it has very mild cams (very Lumpy Tone)

- Passenger-side exhaust is consistently sounding a bit louder, and bubblier/poppy

- Driver-side exhaust sounds noticeably cleaner/smoother/growly (best I can explain it)

- Occasional pops/backfire around 2,500–3,000rpm when having a little bit of a light heavy foot and switching gears from 1st to 2nd

- Constant popping like popcorn while holding the revs at 2,000–3,000 rpm’s

- Low-rpm acceleration can feel heavy or sluggish

- Occasional difficult restarts after the car sits for approximately 5–30 minutes (found this out by the car struggling to turn on after consistently turning it off and on in a long drive through line)

- Cold starts are usually stronger than hot starts, but can still give me issue when cranking over before starting
General Occasional weak starting

- In the past, the engine occasionally stalled after high-speed driving and throwing it in neutral, or while coasting downhill in neutral

- Fuel economy has been approximately 14–15 mpg, even though MOST of my driving is on the freeway in 5th gear with my stock 3.55 Gearing (I know this because I daily the car lot and consistently top off the Car in gas and measure it EVERY TIME by resetting the trip meter)

- Full tank of premium (15.7 Gallons) Last me 230 miles MAX (Mainly Highway Miles)

- The codes always appear while the engine is fully warm and I’m steadily cruising on the freeway (not while idling in my driveway)

This is everything I’ve done trying to fix or narrow down the problem:

- Installed eight new NGK iridium spark plugs

- Gapped the plugs approximately .050–.053 inch

- Replaced the coils with a complete set of used Edelbrock coils off a 99 Cobra That WAS Working

- Swapped the Bank 1 injectors with used set of Bank 1 injectors from another 2003 Mach 1 (24Lb)

- Installed a new fuel pump

- Installed a new fuel filter

- Replaced all four O₂ sensors with new sensors (NTK)
drove around a bit got the code again Swapped the upstream O₂ sensors left-to-right

- Also moved the other O₂ sensors left-to-right during diagnosis

- The problem continued to remain associated with Bank 1

- Swapped the CCRM with one from another 2003 Mach 1

- Cleaned the original IAC then noticed no change also with my idling issue so I ended up, replacing the IAC with a used Lincoln Mark VIII IAC I got from the Junkyard

- Cleaned the MAF using proper MAF cleaner

- Used fuel-system treatment TWICE! (3 month Gap between uses)

- Sprayed brake cleaner around the intake manifold looking for a vacuum leak (Did not notice an obvious idle change during the brake-cleaner test)

- Replaced the passenger-side radio noise suppressor (advice from a friend)

- recently swapped in the MAF from other other 2003 Mach 1 (That WORKS)

The most recent MAF swap happened after the second P0420 just yesterday (August 31st), so I don’t have enough driving time yet to know whether it changed anything, but then again, I’m not sure if it will because if it really was the MAF, then it would be affecting both banks, but we will have to see, it’s more of a why not I guess. But for the most part it has still sounds and feels the same at idle.

The plugs greatly improved the original weakness of power and sluggish starts and cleaning/replacing the IAC from the Lincoln MKVlll helped the stalling, but the uneven idle noise from the passenger-side exhaust end is still noticeably different with occasional popping more consistent condensation, and smoke on cold starts from that side (Bank 1)

I own a set of BBK long-tube headers and a matching BBK catted X-pipe, but I have not installed them yet. I don’t want to install new catalytic converters and possibly damage them if the engine is still running super rich.

At this point I really don’t know what else it could possibly be besides a vacuum leak or some sort maybe but considering that this car is my daily and deeply need to find out what’s wrong with it, I’m willing to spend some money (Nothing Crazy) for a genuinely deep diagnosis from a shop. I don’t want to pay someone just to scan the codes and recommend a MAF or catalytic converter based on the code description. I want somebody to test the fuel pressure mechanically, check pressure after shutdown, inspect the EVAP purge system, evaluate the MAF data, test the injectors and compare the Bank 1 O₂ signals before and after or generally just whatever the procedure might be to crack down on this shit that’s making me go insane!

I would still 110% rather diagnose and repair it myself if possible. I’ve considered buying a smoke machine and compression tester, especially because I can use those tools again. However, I don’t want to keep spending money on tools or parts that won’t actually narrow this problem down.

Based on these symptoms and everything already replaced or swapped:

- Would buying a smoke machine meaningfully help with this specific problem?

- Is a full compression test justifiable?

- What should I test next before paying a shop?

- If I take it in, what specific tests should I require for a proper diagnosis? And how much am I looking at$?

- Could the original rich-running/misfire condition have damaged the Bank 1 catalytic converter and caused the two recent P0420 codes. And how badly do I need to get this fixed before anything else gets fucked up?

- Is there anything else to the 2003–2004 Mach 1 or Ford fuel systems that commonly causes this combination of symptoms?

I’m attaching all six freeze-frame reports along with the list of work completed. I’m looking for a proper direction. The car still runs strong (from what I know) but I’ve always been wanting to overthink everything and not ignore a problem before it turns more severe (talking from experience) so I’m a bit paranoid and just want to fix it as soon as possible so I can make sure that my Mach is not only being as efficient as it possibly can but at its best potential.

I’ve put a lot of time, effort and money into trying to solve this, and I’m honestly reaching the point where I don’t know what else to do. I really love this car and I’m willing to keep it for the long run. I’ve made it to be everything that I’ve ever wanted and I’ve been trying so hard to keep it running correctly, please help me and keeping my baby alive and healthy. I’m more than willing to communicate about any questions or concerns!

Thank you all!

Is there an easier way? We walk up and down the building. Everyone walks, even walks upstairs.

For the last hour or so I have been unable to view my vehicle in the app.

It’s been 3 years since I got this car with all its wonderful issues, so I figured I’d finally post an updated.

I drove this thing 600 miles home and was unaware of its true condition due to the dealership hiding information from me. Long story short, there were cylinders scored and valve seals that were toasted at sub 13,000 miles.

I was out of ford warranty and out of Shelby warranty. Everyone on r/ford and r/fordtech told me I was screwed. Well the dealership ended up replacing the entire long block for free.

It’s been smooth sailing ever since. I love this car even though nobody even knows what it is - only 1 out of 50 ever produced. Shelby does the super snake upgrades every year, but only 2020 got the Carroll Shelby signature upgrade.

My mom called me and asked if I had the app, which I do, but barely use. I try getting in, but it says my email and password don't exist. So I do a password reset and it does work. But I couldn't view the dashboard. But I could get to the home page. And my mom also is locked out of her call at work as a result and may have to call a locksmith.

PAAK is useless unless it works 100% of the time

While driving back from work yesterday, as I’m 10 miles away from home, fuel dropped from 75miles to 0. I left work with ~120 miles to E. Luckily had a gas station 4 miles away and car did let me get there. Shut it off, car won’t start. Added enough fuel to get 200 miles to it. It started and displayed 275 miles to empty.

I am at 16k miles and have a service due this weekend so definitely bringing this up. Just curious what yall think and if its is a serious concern.

Aside from a bad alternator that led me to replacing the injectors twice due to low voltage killing the injectors (i ended up with one extra valve cover bolt at the end of this. Design improvement i say) this truck pretty much only gets turned on for truck stuff. I live on 9 acres of forest and it has hauled and pulled all kinds of stuff over the years in and out of this property. My favorite is making pulley systems in the trees to pull logs up onto my road for easier harvesting. It's fun to just throw some weight around. I know people complain about the 6.0 but ive never had a head gasket issue or bulletproof my truck. I just closed the EGR and put a small tune to increase the throttle response and stayed up on maintenance. It always starts right up and does the work. Honestly I am afraid to replace it.

I’ve got this Fairmont it’s stock height im trying to figure out how much lower will king springs sl or ssl make it? Thanks

- 18 F150 5.0
Had service charging system now message for a few months. Had old alternator seize a few days ago. Replaced belt and alternator from 200 amp to 240 amp. Had battery and alternator tested at auto zone, said Battery health good alternator good, but also said starter was going bad( idk if that would trigger charging system service now message). Ran forscan and this is a picture of the codes I received and then a picture of some readings that I tried diagnosing. My main focus was GENMON 0%. I then put a multimeter on negative battery terminal and pins inside of the 3 pin alternator plug. I got white 12v blue 0v green 0v with vehicle off. With vehicle on I got white 14v blue 0v green 14v. I was trying to find out with wire in the plug might have been for the genmon but I’m not sure how deeper I can so I’m confused at this point and am not knowledgeable enough to understand what those reading are telling me on the 3 pin plug. Thanks to anyone who can teach me about anything I’m doing wrong and what I can do better to track this issue down!

Recently it is getting to where occasionally when I turn on the car, it is on 1610 AM, despite not being on there previously when turning it off.

Hello everyone.

I hope it's okay to ask here.

Anyone already got the Update of the 25SC4 Recall?

Is it true that they limit the battery capacity?

So that the "old"80% Battery Charge is the new 100%?

Because if so, I will try to sue Ford for taking the Vehicle back, bc it doesn't comply to the Contract anymore.

I don't know if it's a worldwide thing or only a European - so I hope it's okay to ask here.

Thanks in advance

The pads that were on my car when i bought it create a lot of dust and have had over 50k miles put on it since i owned it. I dont hear any squealing or grinding yet, but the dust on the rear wheels is concerning

Sorry for the wind noise!

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- May 2025: Fuel pump gasket, oil pump gasket, steering stabilizer

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- September 2022: Power steering pump, transfer case, fuel filter, speedometer drive gear, rear output seal

It's listed at $15,000 and even though it has low mileage, I definitely think that's way more than this car is worth. It is converted on the inside and comes with solar panels, so I know that raises the price a bit.

Thanks for your help!

Is it worth buying a Mondeo ST220 at 18 ? And what are the costs to maintain one ?

hi all, sorry if this isn't the best place to answer this question.

i'm considering buying a non-ford vehicle from a ford dealership. it's only got 23k miles and the original warranty is for 35 more months and 37k more miles, plus it's blue certified. it's also backed by a "90 Day/4,000 Mile Comprehensive Limited Warranty."

i understand that in CA, certified pre-owned vehicles are eligible for lemon law compensation if they meet the following criteria:

• Goes through a manufacturer-backed inspection
• Meets specific age and mileage requirements
• Comes with a manufacturer-issued extended warranty
• Must be sold by an authorized dealership

my question is whether this vehicle would qualify, especially under the fourth point. as the car isn't a ford (nor a lincoln or any other brand they own), does it not count as "authorized" in this sense? additionally, if the vehicle did qualify under those four criteria, i'd only be eligible if an issue popped up within that 90-day/4000-mile period, right?

please let me know if i misunderstand anything or am misinformed. I just want to feel as protected as possible in the context of buying a used car

My sync media screen is only reading Line In and USB it won't let me connect my phone. I was able to connect it one time and now I can't reconnect it again.

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There’s an alert for Key hands on the steering wheel. I always have my hands on the steering wheel, but I often tend to hold the steering wheel more at 8 and 4 instead of 10 and 2. This always causes an alert.

I also used to like to drive with one hand at the top of the steering wheel, but that isn’t allowed either because it blocks the camera that is constantly watching my face.

The issue is not even as much the alerts, but it’s how long they last, and the fact that the beeping will mute phone calls and music.

Any thoughts?

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