All the Symptoms of a Bad Catalytic Converter on a Ford F150

Some of the common symptoms of a bad catalytic converter on a Ford F150 are overall decline in engine performance whether it is slower acceleration or lower fuel economy. You can also expect engine misfiring or your check engine lights coming on from a bad catalytic converter. Sudden rattling sound and exhaust gas smelling like sulfur are some other symptoms of a bad catalytic converter. 

Thankfully you can easily solve the symptoms of a bad catalytic converter on Ford F150. The solution for this problem is not that complicated. However, for that you need to diagnose the problem correctly and be sure if it is even a catalytic converter that is causing the issue. Otherwise you might overlook another critical issue and harm your engine in the long run. To avoid that, let’s get started.  

Common Symptoms of a Bad Catalytic Converter in Ford F150 

Alright, so let’s check the top symptoms of a bad catalytic converter in Ford F150. There are quite a handful you need to watch out for. So let’s go through each. 

Symptom 1: Reduced Acceleration


Proper exhaust flow is the key to operating at peak power for the engine. Now, for that to happen the catalytic converter must be unclogged. If there is carbon build up inside then the exhaust gas will be severely restricted, limiting the overall acceleration of the Ford F150. 

Here is the thing, if you push the pedal from the starting position then the acceleration will be normal. But it starts to get worse as you increase the speed. 

Symptom 2: Reduced Fuel Economy 


As mentioned previously, the proper exhaust flow is necessary for the engine to maintain its peak power. If the catalytic converter is clogged, the airflow will be decreased. Since, we need an optimal air-fuel ratio to burn in the chamber, so lower air means that the mixture will run rich. More fuel burning directly affects the fuel economy of the truck. 

Symptom 3: Engine Misfiring


Clogged catalytic converter restricts the proper flow of air. This makes the overall mixture more rich and also leads to incomplete combustion in the chamber since there is insufficient mixing of air in the air-fuel mixture. A direct consequence of incomplete combustion is engine misfiring. 

Symptom 4: Rattling Sound


This is a serious problem and it happens when the catalytic converter is so damaged that part of the honeycomb structure inside it starts to fall apart due to excessive heat and damage. It gets extremely loud when you start the engine. 

If you hear any rattling noise, then replace the catalytic converter as soon as possible because this can lead to further problems related to engine stalling and starting. 

Symptom 5: Failed Emissions Test 


This happens because of the clogged catalytic converter.Catalytic converter acts to reduce the emission of dangerous pollutants from your truck. But if the cat itself is damaged or clogged then the exhaust is going to be darker and harmful for the environment. So, if your truck is taken to the emission test it may fail. 

Symptom 6: Exhaust Smelling Like Sulfur


Catalytic converter helps to convert the hydrogen sulfide into sulfur oxide. However, if the catalytic converter is not functioning properly then the conversion won’t happen as well. This means that hydrogen sulfide will emit and give a distinctive rotten smell. 

Symptom 7: Check Engine Light Remaining On


Last but not the least, problems in the catalytic converter can also lead to your check engine light coming on. Definitely, your cats will not be the only component that can cause this problem. So, you need to diagnose and look for other sources as mentioned here. 

How To Fix a Bad Catalytic Converter Ford F150?

The good news is that for all these symptoms, the solution is typically leading to either repairing or replacing the catalytic converter. Pretty straight-forward, so let’s dive into each of the solution options. 

Unclogging Catalytic Converter

Over time through the accumulation of carbon buildup, the catalytic converter gets clogged up and leads to problems like decreased engine performance. 

When To Do It? 

You need to unclog the catalytic converter if your Ford F150 is facing the following of the symptoms. 

  1. Reduced Acceleration
  2. Reduced Fuel Economy
  3. Check Engine Light Is On
  4. Failed Emissions Test
  5. Engine Misfiring

With that clarified, you can unclog the catalytic converter in two different ways. 

Method 01 – Adding catalytic converter cleaner to the gas and letting it unclog the cat.

Method 02 – Remove the catalytic converter and soak it into the solution of citric acid for 6 to 8 hours. 

You can also repeat the process using sodium hydroxide. If you are curious to find that out then go check this Cleaning Catalytic Converters with Sodium Hydroxide

How to Prevent Catalytic Converter From Getting Clogged

In the long term you want the catalytic converter to remain unclogged. After all, it is quite expensive and the solution can be heavy on the bank. 

To prevent catalytic converters from getting clogged keep track of the components surrounding the catalytic converter. 

Replacing Catalytic Converter 

This is more serious and you need to do this carefully. This is the step when the catalytic converter is completely damaged and unclogging will not solve the problem. 

When To Do It? 

Replace the catalytic converter when there are the following problems in your Ford F150. 

  1. Rattling Noise
  2. Exhaust Smelling Like Sulfur

So, following are the steps of replacing the catalytic converter on your Ford F150. 

Tools Required

  1. Hammer
  2. Socket Wrench Set
  3. Jack &Jack Stand

Step 1: First, grab the jack stand and place it underneath the truck frame. Jack it up and make sure not to put the jack too close to the body.

Step 2: Find the catalytic converter. It is normally located towards the muffler, about three feets away from the engine. 

Step 3: Tap the catalytic converter with a hammer on both ends to get rid of the formed debris surrounding it. Now, you should clearly see the nuts holding the converter to the mount. 

Step 4: Grab the socket wrench and loosen the bolts by turning them counterclockwise connecting the catalytic converter to the mount. Pull the cats off once the bolts are loose enough. 

Step 5: Install the new catalytic converter by pushing it towards the engine and sliding it back to the mount. Grab the wrench and tighten the bolts by rotating it clockwise. 

Step 6: Finally, lower the truck and remove the jack stand. 

Key Point to Remember While Repairing the Catalytic Converter

In order to repair or replace the catalytic converter, it is important to identify the source of the damage. One such is the O2 sensor. Oftentimes, you will get the error code when there is a problem with the O2 sensor Diagnose the sensor and if there is any problem in it then get the O2 sensor replaced. 

Another component that can cause your catalytic converter to get damaged is the spark plug. Make sure to check that and troubleshoot it. A worn out spark plug means that the fuel will be unburnt or incompletely burnt and this will affect the catalytic converter’s performance. So, replace the worn out spark plug along with the catalytic converter. 

Cost of Replacing Catalytic Converter

Finally, you need to know how much it will take you to replace the catalytic converter. Well, there are two ways you can replace the catalytic converter and let’s see how much it will cost you to replace the catalytic converter on Ford F150. 

DIY Work

If you are into DIY work you still need to pay around a thousand bucks to fix the catalytic converter. Normally, the jack stands should cost you about $20  to $60 and the catalytic converter itself will cost around $1440 – $2000.

So, even with DIY work you will spend around $1460 to $2060 to fix the catalytic converter of Ford F150. 

Professional Service

This is the more conventional method and frankly the one suggested if you are into DIY work on a regular basis. 

The following table should clear out the cost range 

Catalytic Converter CostLabor CostTotal Cost
$1440 – $2000$75 – $150$1515 – $2150

Now, don’t be overwhelmed by the cost of fixing the catalytic converter. It is the best and the most economical option in the long run. 

How To Diagnose a Bad Catalytic Converter on Ford F150? 

Let’s find out the methods by which you can find out the condition of the catalytic converter on your F150.  There are different ways to diagnose any problem and we need to go through each of them. 

Temperature Test

This is the simplest of the steps and requires an infrared thermometer to test the cats. Following are the steps.

Step 01: Start the engine and wait for it to get to the working temperature

Step 02: Next life up the truck and measure the temperature at the inlet and outlet of the cat. You need to use the infrared thermometer for measuring the temperature. 

Step 03: If the temperature reading difference is 10 degrees Celsius or 50 degrees Fahrenheit then your catalytic converter is clogged.  

Exhaust Back Pressure Test

This is the more efficient method to check the condition of your catalytic converter before you try to disconnect the catalytic converters. Do the following. 

Tools Required:

  • Pressure gauge along with hose fitting

Step 01: Find and unbolt the O2 sensor

Step 02: Connect the pressure gauge hose to the spot from where you removed the O2 sensor. 

Step 03: Next you need to start the engine and wait for it get into working temperature. 

Step 04: Check the pressure reading on the gauge. If it is higher than 3 psi or 0.2 bar then that shows the catalytic converter is clogged.

If you want to find out the steps then follow this Ford 5.4 F150 Clogged Catalytic Converter.

Manual Method

This is what you can do if your engine is running low on power and you still need to find out if your F150 catalytic converter is clogged or damaged. Raise the vehicle and wiggle the exhaust system to listen for the rattling noise. If there is any, then the honeycomb material inside the catalytic converter has broken apart and the cats require an emergency replacement. 

For a visual guidance, follow this TEST YOUR CATALYTIC CONVERTER IN 15 MINUTES!.

Vacuum Test

You can also go for a vacuum test to check if the catalytic converter is clogged or not. Use your vacuum gauge and connect it to the intake manifold vacuum. Start the engine and take the reading that should be around 16 to 22 in-Hg. Rev the engine to about 2500 RPMand check for a brief drop in vacuum. 

Don’t worry if there is a drop, the vacuum will return back to the baseline pressure. If the reading takes longer than a couple of seconds to go back to the baseline pressure then the exhaust system is restricted which is most likely due to a clogged catalytic converter.  

With this test, you can also find the problem with other components as well which mostly will be the reason for your engine problems. Of course, the priority here is finding out if the catalytic converter is busted or not but watch out for the following symptoms if your cats are working just fine and the needle rating on the vacuum gauge is not within 16 to 22 in-Hg.

Vacuum Gauge ReadingEngine Condition
Low Steady RatingLeaking Gasket between Intake Manifold and Cylinder Head or Throttle BodyLeaky Vacuum HoseImproper Camshaft Timing or Unsynchronized Ignition Timing
Three to Eight Inches Below NormalIntake Manifold Gasket LeakFaulty Fuel Injector
Regular Drop of Two to Four Inches at Steady RateLeaking Valve
Irregular DropSticking ValveIgnition Misfire
Rapid vibration of four inches along with exhaust smokeWorn Valve Guides
One inch Up and DownIgnition Problems
Large FluctuationWeak or Dead CylinderBlown Head Gasket
Moving Slowly through a Wide RangeClogged PCV system Incorrect Idle Fuel Mixture Throttle Body or Intake Manifold Gasket Leaks

This table should help you find out most of the problems related to the engine through vacuum tests.  

Follow this TEST YOUR CATALYTIC CONVERTER IN 15 MINUTES! to learn more about vacuum tests.  

Using OBD2 Scanner

Now, let’s start working on how to use the OBD2 scanner to diagnose the problems related to the catalytic converter. Grab the scanner and connect it to the OBD2 connector located under the dashboard. Start the engine and input necessary information related to vehicle make, model and engine type. 

Along with that you need to put your Vehicle Identification Number (VIN). Then the scanner will display the error codes. If you are looking for a guide on how to use an OBD2 scanner then follow this How to Use an OBD-II Scan Tool. 

The table below shows some of the codes for a faulty catalytic converter. 

P0420Catalyst System Efficiency Below Threshold (Bank 1)
P0421Warm Up Catalyst Efficiency Below Threshold (Bank 1)
P0422Main Catalyst Efficiency Below Threshold (Bank 1)
P0423Heated Catalyst Efficiency Below Threshold (Bank 1)
P0424Heated Catalyst Temperature Below Threshold (Bank 1) 
P0430Catalyst System Efficiency Below Threshold (Bank 2)
P0431Warm Up Catalyst Efficiency Below Threshold (Bank 2)
P0432Main Catalyst Efficiency Below Threshold (Bank 2)
P0433Heated Catalyst Efficiency Below Threshold (Bank 2)
P0434Heated Catalyst Temperature Below Threshold (Bank 2) 

The table shows the different types of error codes you are likely to find through scanning with the diagnostic tool. But more likely, you will come up with the P0420 code.

What Else You Need To Check For a Fault Code? 

Again, before you throw parts at a problem, make sure that the problem is related to the catalytic converter through the diagnosing methods just described. But if it is not a bad catalytic converter then check the following 

  1. O2 Sensor
  2. Air Filter
  3. Fuel Injectors
  4. Air Leaks
  5. Exhaust System
  6. Unsynchronized Ignition Timing
  7. Engine Parts
  8. Coils
  9. Gas Cap
  10. Spark Plugs
  11. Air Intake System
  12. Exhaust System

Avoid This Mistake During Diagnosing For a Bad Catalytic Converter

Once you diagnose the problem with your OBD2 scanner make sure to look for all the error codes that show up. Let’s assume you find P0420 and replace the catalytic converter. 

But if there are other codes such as the P0300 or P0304 then there is an engine misfiring problem. Ignoring it means your new catalytic converter will go bad in no time. 

The table below shows some of the other error codes you might find and the meaning behind the codes. 

CodesProblemImmediate Step 
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308Engine MisfiringCheck the Engine Cylinder, Valve Train, Cam, Spark Plug
P0171, P0172, P0174, P0175Engine Running Rich or LeanCheck for the Air-Fuel or O2 sensor

Looking for further codes in the diagnostic tools will save up a lot of your time and cost. So, make sure to avoid the mistake of getting into action only after seeing the code P0420. 

Summary: Watch out for other codes along with the bad catalytic converter codes such as P0420. Because there might be underlying issues that need to be addressed as soon as possible or else the problem will keep repeating. 

How Long Can I Drive With a Bad Ford F150 Catalytic Converter? 

Let’s assume you are in a situation where you can’t just stop in the middle of nowhere and get your cats fixed. In that case, it is natural to think if you can carry on like this or not. Don’t worry about it because this section covers exactly that.

Check through the table below for information related to duration and the catalytic converter states. 

Catalytic Converter ConditionSymptomsDuration You Can Drive
Partially CloggedEngine Misfiring, Loss of Acceleration PowerYou can drive up to the nearest servicing station
Completely CloggedEngine IdlingYou can not drive, consider replacing
Burnt or DamagedStarting ProblemsYou can not drive, consider replacing

So, normally your catalytic converters will get clogged or completely damaged. If the cats are partially clogged then problems like engine misfiring will occur and loss of acceleration power will happen. In that case,  you need to drive slowly and go to the nearest servicing station as soon as you find one. 

But if the cats are completely clogged or burnt and damaged then you will face engine idling, rattling noise or starting problems. When that happens, stop everything and get your truck towed to the nearest servicing station. Attempting to drive the truck in this condition causes severe damage and puts the driver’s life at risk. 


How Long Do Ford F150 Catalytic Converters Last? 

Ford F150 Catalytic converters last for about 1,00,000 miles or 10 years if you make sure to maintain the engine and the ignition system properly. Of course, your catalytic converters will go bad a lot sooner if oil or coolant leaks into the combustion chamber from worn out gasket or piston rings, or if you use the wrong type of fuel. 

Am I Hurting the Environment By Driving With a Bad Catalytic Converter on Ford F150? 

Yes, you are hurting the environment by driving with a bad catalytic converter on Ford F150. Catalytic converter works to reduce the overall exhaust pollution through filtering out the harmful byproducts in the exhaust gasses. With a bad catalytic converter, none of these pollutants will be filtered and the exhaust gas will keep deteriorating the environment. 

How Long Will Be the Warranty for Fixing Bad Catalytic Converter of Ford F150?

The repair shop warranty for fixing bad catalytic converters of Ford F150 should be a minimum of 12 months and 12,000 miles if you go to a RepairPal certified shop to diagnose any catalytic converter related problem and look for a solution. Beyond that, they analyze the problem deeply and offer a fair price for their services. 


Now,that will clear out all the doubts you might have regarding the symptoms of a bad catalytic converter on Ford F150. Keep an eye out for the symptoms and based on the situation go for the solution.

But while you diagnose make sure to watch out for any other potential source of the problem and finally keep the cost of repairing the cat in mind.

Leave a Comment

Written By

Photo of author

William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

Fact Checked And Mechanically Reviewed By


Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.