Misfire Mishaps

[thousandlegs]

I have a 96 I30 that I purchased not too long ago. The car has 164000 miles and when I bought it it ran perfectly. Within a couple of weeks it began to miss. I went to the parts store and they read the codes that showed a misfire in cylinder 4 (p0304). Since I bought the car I have:

Changed the oil and replaced with full syntheticChanged the spark plugsReplaced the coil on cylinder 4Used SeaFoam in the brake booster and in the gas tank

Here's the deal...there is a pretty major misfire and studder below about 2500 rpm. It is especially noticable when idling and in gear. Also, it seems to do it more after the enging begins to warm. I didn't do any of the things listed above until after the studder began. I'm stumped as to what is wrong. Can someone please shed some light on the situation for me?

[halcyon87]

does ur i30 stall at a light or stop. if so it could be the MAF and might need to be replaced cuz when i bought my i30 it started stalling at a light/stop or idling and also studder and couldnt break the 2000rpm. And it didnt even trigger the CEL so you might wanna have that checked too.

[coolhand]

Check the compression on that cylinder. If it is fine, it maybe the fuel injector. Common on Nissan engines.

[thousandlegs]

I don't have any trouble breaking 2000 rpm...it seems to run fine over 2500 or so. How would I check the compression in the cylinder? Also, is there any way to repair an injector or would I have to buy a replacement?

[maxhopper]

What kind of spark plugs did you use for replacements?

[thousandlegs]

I forget what brand but they were platinum and the computer at Wal-Mart said that they were the recommended plug for the car. The misfire/studder began before the plug change though. I also changed the fuel filter, which was completely crudded up...couldn't even blow air through it.

[maxhopper]

Your initial misfire could have been caused by 1 or more bad plugs, but installing 6 incorrect plugs would not help. I would advise installing only NGK plugs for the I30/Maxima. Other brands have shown to cause a rough idle condition.

[coolhand]

I don't have any trouble breaking 2000 rpm...it seems to run fine over 2500 or so. How would I check the compression in the cylinder? Also, is there any way to repair an injector or would I have to buy a replacement?

The Compression test tool can be found at any part store. You could rent it for a day. The injectors can be cleaned but with the history of Nissans injectors it would be better to have it be replaced. Incorrect spark plugs can cause a rough idle, but if you have a misfire in one cylinder it could be more to it. Start by changing the plugs out with NGK or Denso platitums plugs and check the cylinder that is misfiring with the Compression tool (perfect time to do this) make sure that all the coil packs are unplugged andscrew the tool in the spark plug hole of the misfiring cylinder. Try starting the car (let the engine turn over for 3 -4 seconds) if the gauge on the tool reads around 110 - 150psi your ok, lower than 100psi engine problems.

[thousandlegs]

Thanks for all the advice guys. I'll try those things one by one as soon as (financially) possible.