Q: P0302 2003 Pontiac Aztek

asked by on March 09, 2017

The car has code po302, misfire in cylinder 2. The vehicle recently had a major tuneup, and we checked the following:

  1. plugs
  2. wires
  3. ignition coils
  4. cylinder compression- is 130 PSI
  5. We replaced the fuel injector for cylinder 2
  6. we changed the gas filter which had nothing to do with it anyway.
  7. used two bottles of lucas fuel injector cleaner. one bottle per full tank of gas.

It is an intermittent misfire. The car seems to run a little rougher when cold, and warming up. if you jump on it from a dead stop, it will misfire almost all the time. The check engine light comes on and is flashing. It then goes off. if you reset the code, the check engine light comes back on about a week later and shows the same code again. I just drove the car 75 miles on the freeway, It seemed to not be misfiring on the freeway, then i noticed it at higher speeds 50-65 mph or around there. it then rides normal at high speeds of 70-75 mph.Vehicle computer may adjust to problem?

My car has 108000 miles.
My car has an automatic transmission.

Spark Plugs Replacement $96.63 - $636.71 Get a Quote

Hi there - if I’m reading your notes correctly, you "checked" the plugs and wires, but did not replace them. For your mileage, you need to replace the spark plugs at least, and possibly the plug wires as well. Misfiring under load is a primary symptom of weak ignition components. I recommend spark plug replacement performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, replace the plugs, and get you back on the road smoothly again.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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

What others are asking

New thermostat new coolant temp sensor car is still going into red and overheating what do i do

You should first see if the electric cooling fan is coming on before it overheats? If they do not come on then the fans needs checked to see what is keeping it from coming on? It may be a fan...

Headlights stay on

Hello. This sounds like the headlight switch is faulty. You might also want to check to make sure you have the headlight switch in either the auto position, or the off position. If the headlight switch is left in the...

My car is wasting water alot i have to put water in it every morning there is no visible leaks i changed the radiator and the radi

Hi there. Typically when the vehicle is using a lot of water it's because you're using water instead of coolant. Coolant is designed to heat up, while water will evaporate much quicker when the temperature rises inside your motor. It...

Cooling fans

This can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning...

Transmission problems

A diagnostic is only meaningful if there is a specific identification of a part or parts that have failed, are worn out, defective or the like. The bearings in the differential that you refer to are not visible for inspection,...

temperture sensor

VW / Audi has had lots of "issues" with sensors in the early 2000 model years. 2003 is one of them. The coolant temperature sensor is one of the most common. While it's not unusual for a coolant temperature sensor...

AC not taking coolant

Hey there. You may have a bad A/C compressor if you see the compressor engage but the high and low pressures stay the same. If the high pressure spikes above 300 or more, then the compressor can produce pressure but...

Transmission won't go into gear - 1997 Pontiac Grand Am

Hi there. Unfortunately, performing a transmission flush can create more problems for the transmission than it helps, especially with higher mileage. The debris gets stirred up and travels throughout the transmission. A transmission service should involve dropping the transmission pan,...

Brake lights staying on

The brake light switch has a small rubber bumper that pushes in on it to keep the light off. The rubber bumper falls apart with age and then the brake lights stay on. The bumper on the brake pedal linkage...

Related articles

Symptoms of a Bad or Failing Ignition Coil
Common signs include the Check Engine Light coming on, engine misfiring, rough idle, a reduction in power, and the car not starting.
Symptoms of Bad or Failing Spark Plugs
Common signs of faulty spark plugs include slow acceleration, loss of power, poor fuel economy, engine misfires, and difficulty starting the car.
Is it Safe to Drive With a Misfiring Engine?
Repairing a misfiring engine can be simple or complicated, depending on the reason it is misfiring. The most common causes of engine misfires are:...