Can a Bad O2 Sensor Cause a Misfire?

A bad oxygen (O2) sensor cause a misfire by sending the computer incorrect information. This article reviews a 2004 Nissan Titan where the O2 sensor caused a misfire, giving the truck misfire symptoms, misfire trouble codes, and additional trouble codes.

Diagnosing an Engine Misfire

In this specific case, my 2004 Nissan Titan would almost stall at idle, there was some hesitation when accelerating, and I could feel some vibration from the engine intermittently. All of these symptoms could be attributed to an engine misfire, so when the check engine light came on, it wasn’t a huge surprise. What was a surprise was the number of fault codes the ECM (engine control module) threw. In total, my OBD reader found five fault codes:

• P0300 - Cylinder Misfire Detected Random Cylinders
• P1288 - Air Fuel Ratio Sensor 1 Circuit Slow Response Bank 2
• P1289 - Cylinder Head Temperature Sensor
• P1168 - Closed Loop Control Function Bank 2
• P0430 - Catalyst System Efficiency below Threshold Bank 2

As you can see, the biggest question was where to begin. Typically if you have 1 or 2 faults codes show up, it can be easy to identify your issue, but this was something different. Each of these fault codes has its own set of troubleshooting steps to identify the issue.

Was I going to drop the truck off at the shop and spend hundreds of dollars just to have them tell me what’s wrong, or dive in and try to figure it out myself? Seeing as it was winter here in New England and I didn’t have a garage to work in, sending it to the shop was very appealing, but I just couldn’t justify spending that kind of money on something I more than likely could do myself.

Possible Causes of a Random Misfire and Solutions

Spark Plugs

As mentioned before, when the check engine light came on, the engine had already been running a little rough. The P0300 said it was a random cylinder misfire and really didn't give much information other than that. In the 4 years I’d owned the vehicle, the spark plugs had never been changed. I figured that would be a good place to start.

I picked up some spark plugs and, when I got home from work, I dragged out my spot lights and got to work in the driveway. After an hour or two, my hands were freezing and I had a couple scraped knuckles, but the truck had eight brand new spark plugs and it was time to start it up to see if anything had changed. All hope was lost. After starting the truck, it displayed the same symptoms as before.

Bad Ignition Coils, Air Intake Leaks, Dirty Mass Air Flow (MAF) Sensor, or Engine Control Module (ECM) Failure

The next day, I decided I needed to reach out to a few automotive friends and explain my dilemma. The general consensus given the symptoms prior to the light coming on, was that I was heading in the right direction. Suggestions I received ranged from switching or replacing ignition coils, checking the air intake for leaks, or cleaning the MAF (Mass Air Flow) sensor, to checking for ECM (Engine Control Module) problems, among many more. The possibility that it would be a bad ECM was a little unsettling, because of the potential cost of replacing it.

Bad Oxygen (O2) Sensor

The suggestions I received seem to be all over the map, so I decided it was time to do some of my own internet research. What I came across was a lot of forum discussions and a lot of people frustrated with the fault code P0300 because of the lack of information it provides. I even typed “Nissan Titan P0300 P1288 P1289 P1168 P0430” into Google as an absolute Hail Mary that someone had the same exact issue. No surprise, I didn’t have much luck with that. I did however come across one forum post where the writer described something very similar to my problem, so I read the whole thread. After a lot of back and forth on that particular post and the writer replacing and testing multiple parts, it ended up being an O2 sensor that solved his problem.

Inspecting the Air Intake

Now that I had a few potential causes for my issue, it was time to decide what to try first. I didn’t want to spend money on parts I didn’t need, so my thought was to check anything that cost little to no money at all. I first checked the air intake for any leaks or cracks in the intake hose. Everything checked out fine in that department.

Cleaning the MAF Sensor

Next I pulled the MAF sensor, which is mounted in the intake hose. I had heard that even if the sensor looks clean it could be dirty enough to be sending incorrect messages to the ECM, which in turn can affect the air fuel mixture in your engine. I cleaned the sensor with mass air flow cleaner and reinstalled it. After starting the truck, there was no change—still running rough. It was now time to start replacing parts.

Could a Bad O2 Sensor Cause Rough Idling?

The concept that an O2 sensor could cause a misfire seemed crazy to some people I talked to, but my gut feeling was that the forum post I read was right. I ordered a brand new O2 sensor from 1AAuto.com and it was at my door the next day. Luckily, I already had the special O2 sensor socket but 1A Auto had that for sale as well.

I got home from work that night and again pulled out the spot lights and tools to evaluate the situation. The fault code P1288 identifies the O2 sensor location as sensor 1, bank 2, otherwise known as the front or upstream sensor on the passenger side of the vehicle. To learn the difference between the upstream and downstream O2 sensor, check out the video below.

The location of this sensor made it difficult to get to. It was mounted in the exhaust manifold right next to the inner wheel well and frame rail.

I didn’t want to take the time to remove the wheel and take the wheel well liner out. After crawling under the truck, I noticed that there was just enough room to get the socket and ratchet over the O2 sensor next to the frame rail—very tight quarters but doable. Just my luck, the old sensor would not budge. I had to pull out my trusty breaker bar (aka a small piece of pipe to put over the end of my ratchet), essentially extending the ratchet to give me more leverage. Finally the sensor broke free and I was able to remove it the rest of the way by hand.

Now that the old sensor was removed, it was time to install the brand new O2 sensor. Again I crawled under the truck and was able to install the new one the same way the old sensor was removed. It was the moment of truth: was my gut feeling right? I started the truck and it purred like a kitten—no rough idle at all! I took it for a quick test drive around the block and it ran great. I was ecstatic!

How the O2 Sensor Caused a Misfire

Because the truck was running great my theory now was: because the O2 sensor was telling the ECM the engine was running lean, it was dumping more fuel into the engine. This caused random cylinders to flood with fuel and not fire. It also caused other cylinders to fire with too much fuel, causing the cylinder to be hotter than normal, explaining “P1289 - Cylinder Head Temperature Sensor”. When one cylinder did not fire, it was dumping that fuel out the exhaust which could have caused “P0430 NISSAN - Catalyst System Efficiency below Threshold Bank 2”.

The other three fault codes P1288, P1168 and P1283 could all be attributed to the bad O2 sensor. With this new theory in mind, I decided to clear all the codes from the ECM and hope the check engine light wouldn’t come back on. I have now driven over 1,000 miles and the light has not appeared again.

I guess the moral is, working on your vehicle outside in the winter stinks, but by ordering my parts from 1A Auto and doing the repair myself allowed me to save hundreds of dollars and learn that an oxygen sensor can in fact cause a misfire. The sense of accomplishment I got from fixing my own vehicle wasn’t that bad either.

Learn to Replace an Oxygen Sensor Yourself

Check out the video below and learn the steps for replacing an oxygen sensor yourself. Find out how to replace the oxygen sensor on many makes and models with the 1A Auto how-to video library.

Need an Oxygen Sensor Replacement?