hello, looking for some help here.

hava a p0304 (or what ever the misfire in cylinder 4 is)

missfires at iddle only...and throws the code consistently.
changed coil that goes to 4
chaged spark plug on 4
tried a different wire on 4 (certain it isnt wire and it didnt burn on headers)
even changed 2 and 4 injector

was just wondering is there anything else besides low compresion on that piston that will cause this?

another note......... my catalyst is rattleing going to change it out on Friday that couldnt be it could it?

thanks for any help in advance,
if you need more info please ask.

Im trying to make it pass smog to keep it as my daily driver.

 

The injector for #4 may be cloged or not firing.

 

How could an 02 sensor that reads a bank of cylinders know that one injector is clogged? Not firing electrically, I can buy that though.

 

swapped out injectors and still misfire on #4.............

 

Misfires are picked up by the Crank Sensor. Where the did the O2 sensor business come from? lol

 

When you said the injector could be clogged. But that would cause a lean bank condition, picked up by the 02 sensor.
Are you saying the crank sensor can detect one lean spraying (clogged) injector?

 

You could try to change the plug and wire for 2. The way the coils work it could cause an issue. How did the plug look? Have tried a spark tester to see if it is firing? It could also be the Module or a small coolant leak into the cylinder.

 

To set a misfire DTC, the PCM looks at the output of the crank sensor and wants to see a momentary (Milli sec) increase of rotational speed of the crankshaft whenever a particular cylinder fires, if instead of speeding up the crankshaft slows down, a misfire is recorded. A misfire in one cylinder that is getting some fuel will probably cause the O2 sensor to see a rich mixture (unburned fuel in the exhaust). If the misfire is due to complete absence of fuel, then the extra air in the exhaust will probably make the O2 sensor see a lean mixture. Either way the PCM does not look at the O2 sensors to set a misfire DTC.
The crank sensor does not know or cares about what causes a misfire, the only thing it does is to report the crank position to the PCM every so many degrees of crank rotation.

 

Ahhhh ok. So in a lean cylinder condition for instance, the crank sensor is picking up a momentary drop in power in that cylinder, then assumes it's a misfire. That's what was throwing me with what you said, I've never considered a lean fuel supply issue a misfire, but the PCM does because it doesn't know any better.

 

That is what I was trying to say, but many times I confuse myself.