Any idea of what might have thrown this code? I actually never felt a misfire, I turned the car over and noticed I had an SES (which for me is normal, I get P0140 for o2 issues due to TP) but it also pulled the P0300. I reset it and drove home, the car felt like it was pulling fine, no sputtering/bogging under WOT. You herd of any issues with misfires of the 4b11T Nozie, and if so what were some of the causes? Have been hearing an array of things from simply fouled plugs, to bad injectors, to scary **** like bent valves...its kinda of got me bent a bit.

 

I'd check the plugs first. Did it only throw the code once and hasn't come back?

- Bryan

 

Hasn't come back (P0300), but its only been like 15miles at most since the reset, and this is the first time (at least that i've noticed) it has thrown the code. I never actually felt a misfire, I actually went to turn the car over last night leaving Los Gatos, and decided to reset my P0140 for my TP and noticed that the OBDII code reader had another code (P0300)...really freaked me out. Going to roll the car over to Mike and have a looksy at the plugs. I still have those extra plugs laying around so If my plugs are fouled hopefully we can swap them.

 

Like Bryan said, check the plugs. Pull them and see if they are uniform, and none are hammered shut.

I have never heard of a PO300 on an Evo X before now. If the plugs look fine, I think you can afford to relax somewhat if the problem has not come back.

 

Thanks guys, I'll keep you posted on findings, after inspection of the plugs and whatever else we might think could have caused this.

 

I have seen this issue on a car with a set of DW 800cc injectors. Turns out, there was a faulty injector which DW happily replaced.

I am currently having this issue on my car as well. It runs fine under boost, but idles like crap. I have backflushed all of the injectors, gapped, and inspected all of the plugs. My next thing will be replacing the plugs. I really don't think it is a coil.

 

Hey bryan, im going to roll through saturday morning/afternoon and do plugs and look a few things over. Mike said to ask if you get a chance to look over my map, as lately my car has been hating idle. Usually after a descent drive @ highway speeds (I work in Oakland) when I come to my first stop inner city ( light) the car will have a bit of a stumble (AFR's will go off the chart to 17.1) for about 10-15 seconds and then it somehow recovers to keep it from stalling. Doesn't happen all the time but thats usually how I can get the car to do it

Just drop me a PM what time might be good (all day is good for myself). Figured it wouldn't take long.

 

I got this today coupled with a couple P0304 and 0301's. I think my plugs are jacked. I checked my fuel filter (it's one that comes apart) and it looks great.

30,600 miles... the last 100 were REALLY hard

 

went out and pulled the plugs. Look fine, but I guess I'll replace them anyway.

 

Mine looked great and were all gapped correctly. Installing the new plugs fixed my 0300 and 0303 codes. In fact, it hasn't run this smoothly in a month or 2.

 

Good to know. What plugs did you replace them with? Stock? HKS? NGK? I cleared my P0300 when it first happened and have yet to see it come back again. I'm under the impression it was a phantom code. I will pull my plugs tomorrow (was crazy busy this weekend) and have a look at them. I already have replacement plugs ready if necessary (HKS M 45XL).

 

rfielder replaced with stock (as I'll likely do as well).

[I talked to him about it yesterday]

 

Nice! So how does it feel? Did you actually feel the car misfire?

 

I could feel my car misfire, mainly through the mid range RPM (3000-5500). It also had a very rough idle. Even though I have stock cams, it still sounded like it had some very lumpy cams in it.

 

I just got the P304 cylinder 4 misfire code too.