My 2000 Lexus ES300 started misfiring and threw a p0303 code. I changed the coil in cylinder 3, and the problem stopped for 30 minutes and started again. However, now it only starts misfiring while accelerating and stops misfiring once cruise control is set and the car is coasting. Has anyone else had similar problems? If so, how was it fixed?

Thanks for any input

 

could be a spark plug or injector issue if you already changed the coil.

spark plugs are easy to change when was it last changed?

injectors are more difficult, and requires the intake manifold to be removed.

there are a few tests on youtube on how to check for bad injectors.

the screwdriver method to listen to the pulses, the ohm method to check proper resistance, if you have to remove it, you can also clean it with a tire valve and carb cleaner while briefly connecting it to a power source.

 

Do quick and dirty.

Move the front (easier access) coils around and see if the misfire moves. If so then it is the faulty coil affecting the rear connector.

This is how I found a misfire on #1. I moved #2 to #4 position and the misfire moved along with it.

You could replace the rear plugs like I did ( it was warrantied at Oriely's) but it did not help the misfire to #1.

 

did you replace with oem ignition coil ?

 

Also, the ECU is not always as smart as we think it is. Sometimes the misfire is on an adjacent cylinder.

 

yeskay, if you are writing to me. YES, lucky I had some good older OEM's. removed failed aftermarket ones. Geez, even the rubber parts were falling apart on the aftermarket POS.

artbuc, funny you wrote that. That is exactly how it happened to me. I was expecting #3 to miss when I swapped #2 to #4 but swapping made #5 miss, WTD???

 

Update:
I haven't been able to get on the forums recently. After changing the coil in cylinder 3 it started to misfire again. I changed the spark plug in cylinder 3. Got a Bosch iridium plug. The one in cylinder 3 had been replaced before. It wasn't an iridium plug, checked all other spark plugs, all spark plugs that had been changed by the prior owner are the incorrect kind. No more misfiring though! (For now)