Engine Check Light: P0301 - Cylinder 1 Misfire

[boredstudent3]

Hi Guys,

So the unfortunate happened. I saw the engine check light and after i pulled the code, it was P0301 which meant "cylinder 1 misfire".

now the preface, the night before the car was running perfectly fine. nothing unusual from the daily drive, sounds of the car were perfectly fine. nothing deviated from the norm. i parked it on the driveway and went inside for the night.

on saturday morning (it was windy, cold, and raining) i went out to start the car. now it normally jumps to ~2000 RPM and then as the car warms up, it slowly drops to ~1000 RPM.

it did not do this on saturday morning. it went to ~1100 RPM and stayed there at idle. this is out of the norm. i went back inside and when i came back out the engine light was on.

after pulling the code, "cylinder 1 misfire". what do you guys think could have caused this overnight? the only thing that changed was the weather.

i changed the spark plugs several months ago. the spark plug wires are OEM (98 corolla, 186,000 KM). everything "ignition" wise is OEM. someone said to me that it maybe the spark plug wires b/c they're old and the insulation may be bad. combined with the wet and cold weather from saturday morning, this may have shorted it out. although i didn't see any visible sparks from the wires itself.

so, what do you guys think is the problem and what should i try first to resolve it? i am planning to change out the 4 spark plug wires first.

another question to clarifiy as i've been hearing different answers. does the 98 corolla have ignition coil or distributor or coil on plug (COP)? i'm VERY confused with regards to this.

thank you for the help guys.

[fishexpo101]

The 1998-1999 model year Corollas for the North American market have separate plug wires and a pair of coils. Only the 2000+ model years have coil on plug units (1ZZ-FE engines with VVT-i)

Your diagnosis sounds good - definitely check out the plug wires. If you have access to a multimeter - measure the resistance of the plug wires. Also, remove/replace them one at a time, so as to not get the firing order messed up.

I wouldn't rule out a bad plug - would be a good idea to plug the spark plugs and read the ends. The OEM plug is the dual prong type, make sure that one of the ground electrode did not get bridged with carbon/other debris and cause the plug to misfire.

[boredstudent3]

Originally Posted by fishexpo101

The 1998-1999 model year Corollas for the North American market have separate plug wires and a pair of coils. Only the 2000+ model years have coil on plug units (1ZZ-FE engines with VVT-i)

Your diagnosis sounds good - definitely check out the plug wires. If you have access to a multimeter - measure the resistance of the plug wires. Also, remove/replace them one at a time, so as to not get the firing order messed up.

I wouldn't rule out a bad plug - would be a good idea to plug the spark plugs and read the ends. The OEM plug is the dual prong type, make sure that one of the ground electrode did not get bridged with carbon/other debris and cause the plug to misfire.

it was a bad sprak plug wire going to cylinder 1

i pulled the plug out and saw that the inner metal part of the wire was stuck to the end of the spark plug...basically it was disconnected inside the engine block

i should have changed the wire set at the same time as the spark plugs 3-4 months back...would've saved me the trouble of not having car for 2 days and worrying about the cost of repair when seeing the CEL...