Car has 155K miles on it. Started to run rough and code indicated cylinder 4 misfire. Swapped coils 3 with 4 and misfire moved to 3 so I replaced all coils and plugs. Now when driving it's running rough again but this time it's indicating misfire on cylinder 1. I was trying to DIY it but there are so many possibilities.

Anyone else run into something like this?

 

What were the codes?

 

First code was P0304. Swapped coils w/# 3 cylinder and then got P0303 so I figured it was a bad coil. Replaced all 4 coils and plugs and now its getting code P0301.

Cleaned the MAS and still getting the code. Seems to rough idle once it's warm and gets worse when driving.

Thanks for replying.

 

Check that the EGR valve is closed. Coil wiring connections. Coolant temp sensor.

 

thanks, I appreciate your help.

 

So, here's the latest. I took it to Toyota and they diagnosed it as a bad spark plug even though it was a new NGK plug. Anyway, car ran fine for about a week. Now it's misfiring again and the two codes I got this time are P2237 and P0354. I guess I should take it back in but I don't want to keep dumping money into it if it doesn't fix the issue. It now has all new plugs and coils...they are aftermarket NGK plugs and Duralast coils.

I've read P2237 is the upstream, AF O2 sensor. I'm hesitant to just replace it as I'm wondering if the misfire was caused by something else. Sorry, very frustrated. I'm a diehard Toyota fan and have never had problems before.

 

P2237 is open or short circuit for Bank 1 Sensor 1 A/F sensor. It could be a bad sensor, bad sensor heater (bad sensor), wiring or EFI relay. Most likely a bad sensor. Someone with a scanner can narrow down the problem area assuming the sensor is the problem. Is the check engine light on?

This issue can cause the engine to run too rich as the fuel system doesn’t know the real time air/fuel ratio and defaults to a fixed computer program to set the ratio.

P0354 is back to ign coil D primary/secondary circuit as in No 4 cylinder?