Q: Q: Cylinder 3 misfire

asked by on

I have a 2003 Pontiac grand am with a little over 152,000 miles. I've recently got a p303 cylinder 3 misfire code as well as a code for insufficient egr flow. We replaced the egr valve, spark plugs and wires. The insufficient egr flow code disappeared but the check engine still read cylinder 3 misfire. So we replaced the coil pack for cylinder 3 and reset the code. The car drove fine/normal for about 20 miles and then started to run rough again. The check engine reappeared with same code cylinder 3 misfire, no other or new codes. I was told I should change all coil packs and not just the one for cylinder 3. I think I'm just being sold unnecessary parts because why would a bad coil pack on cylinder 1 or 5 cause cylinder 3 to misfire? Is the coil pack really to blame or is it something else? I really have little to no knowledge about cars and would just like another opinion. Thanks!

My car has 152500 miles.
My car has an automatic transmission.

The "suspect" coil should have been tested prior to replacement; there might not have been anything wrong with it or the terminals might simply have needed to be cleaned (sometimes the terminals will get rusty or corroded). The other coils are irrelevant to the issue in cylinder No. 3. Among the causes of individual cylinder misfiring are faulty spark plugs, low compression, damage or excessive wear of spark plug wires and/or coils, faulty fuel injector, clogged EGR valves or tubes, burned valves, improper ignition timing, vacuum leaks, leaking head gasket, faulty camshaft sensor, faulty crankshaft sensor, faulty mass air flow sensor, faulty oxygen sensor, faulty throttle position sensor, faulty catalytic converter, and others. If you want the cause in your case pinpointed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a misfiring diagnostic and the responding certified mechanic will get this diagnosed and resolved for you promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Q: Cylinder 3 misfire

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: When im at stop light press on gas car jerks

Hi There, It sounds like your vehicle may be a bit low on transmission fluid or you may potentially have a bad transmission control solenoid. As you know, the transmission works on hydraulic pressure built up from the fluid inside...

Q: Q: My car cranks but won't start.

Hello, thanks for writing in about your 2002 Pontiac Grand AM. There are several possible causes for a vehicle to not start. There could be a fuel supply problem, an ignition problem, or even a failed sensor. For an issue...

Q: Engine is over heating and I'm not getting heat. 2001 Pontiac Grand Am 3.4 V6

Hello - I agree with your diagnosis - a water pump failure is a prime candidate for both overheating and a "no heat from the heater". Lack of water flow will cause both symptoms, and cause damage to the engine...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...