Question

Getting a PO303 - Cylinder 3 misfire detected. This only happens on hot day after driving for awhile and restarting the engine after it's been parked for a few minutes. The rough idle goes away after 1 minute of engine running. What could be the problem? Spark Plug? some overheating issue?  Please help. Thanks

Answer 1

Check the #3 coil and its wires. Check the spark plug and the injectors

if you have not replaced your spark plugs, you might want to consider it.

other solutions may be to,

- Perform Injector Service if neeeded
- Replaced Spark Plug #3 if needed
- Replaced Injector #3  if bad
- Replaced Ignition Coil #3 if bad

Answer 2

When you say ignition coil, do you mean distributor cap, wires or the whole $200+ distributor coil? I just ordered some good Pulstar Spark Plugs, a new knock sensor (also had a PO325 code) and new intake manifold gaskets. Hopefully this will fix the issues. I'm currently running with Nology spark plug wires, you think these might be going bad? I've had them for two years, only put 15k on the car since then. Any good way to test them?

Thanks for answering! Cheers!

Comments

if you have a coil pack check and see if its not broken or melted. If you have a distributor cap you should check the wires.
I would say away Pulstar Spark Plugs, I know people who had them and they work but they run so hot they melt the coil packs. Cant go wrong the same brand as the orginal plugs, or platinum tipped spark plugs.

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when checking spark plug leads or HT leads, first off you will need a multi meter set to ohms 20k or more, the formula is 15k ohms for every 1 meter in lenth.  So you will need to measure the lenth of your leads one at a time and do the math, eg, .5 meter lead should read 7500 ohms, .25 meter lead 3750 ohms.  any plug lead with a high or low resistance would indicate a bad lead. a test worth doing before you spend money on other ignition parts.

Answer 3

If the problem happens only happens after the conditions you mention, then the problem sounds more like bad fuel injector.