Skip the auto shop - Our mechanics make house calls

Q: Random misfires

asked by on

About a month ago, I started getting misfires at random times. Since then, it has gotten worse. When the car starts up like normal, every three seconds, it will misfire, and the catalytic converter gets hot - hot enough to turn red. The code reader just gives me "P0300" - random misfire. I have checked the coils, and they were fine. We switched them out anyway, and that didn't help. We tried using three ignition control modules, but there was no change. A new ignition coil went in yesterday, because the old one had a slight burn mark and was arcing. When I changed it, the car ran fine for a second, then went back to misfiring. There is a lot of clear condensation coming from the exhaust, but I don't think it is anything bad like coolant or oil. What could be causing these misfires?

Hello. There are several possibilities that could explain why you are having this problem.

  • One possibility is that you could have one or more faulty fuel injectors, or the fuel injector wiring is damaged.

  • Another possibility is that one or more spark plugs have fouled out.

  • It is also possible that there are bad internal engine parts.

I would suggest that you have a certified technician, like one from YourMechanic, come out and diagnose your car to find out why your engine is misfiring.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Random misfires

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My 2003 Honda Accord European has developed a gearbox transmission issue.

Hi there. When the transmission is not shifting then this is a condition called limp mode. The computer put the transmission in limp mode for a fault that the computer picked up. Check the wiring harness to the transmission and...

Q: cylinder misfire

There seems to be a variety of symptoms going on at the same time. Addressing the ticking issue, it could be your lifters, and it could also be your fuel injectors. This could be part of the problem when it...

Q: Car won't shift,smoke coming from underneath,leaking transmission fluid.

You will need to have the transmission leak pinpointed to isolate the source of the issue. If one of the lines are leaking then it can be repaired but if the front pump seal is leaking then the transmission would...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.