Welp,

Today I had the CEL come on and I went over to vatozone and they said the code I was getting was P0301, so good 'ol cylinder missfire on #1. Long story short, I've noticed the CEL come on and then go off every once in a while for the past like year or so. My car has 73k miles on it. The light would usually take a couple of days to stop. Today the light came on, and then I pulled the code, then drove easily over to a car meet and when leaving the meet; I noticed that the CEL was gone. So I flogged the car in the mountains for hours...and nothing, the car ran strong.

When the CEL light was on, there was no noticeable change in power, and at idle, the car was not popping or any audible backfire that would really catch my attention as a misfire. I did flog it occasionally for testing purposes and the car didn't sound abnormal and no hestitiation in power delivery from what i could perceive.

My idle is lopey and ever so slightly rough from the Nismo cams. The dealer bumped up the rev to 700rpms when they did the cam install and the car has idled like it has ever since.
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My car has Nismo cams, jwt intake, crawford Z plenum, ur pulleys, no cats, and borla td exhuast. I did notice that this is a distinguishable hiss from the engine bay at idle like as if air is coming out somewhere or something, (I've heard this sound for a while and thought about possible leak somewhere in the plenum or something...?) I wonder if this sound could play some sort with a misfire. The temperature got up into the 100 degree range today, but even prior when the CEL came on before, the temperature was cooler etc, and sometimes I've gotten CEL's when going on 'cruises' in the mountains which is usually full throttle runs.

Also, my AC is not working! Aside from the engine misfiring, the AC is not clicking on, like as if something electrical. (Can anyone recommend the location of the fuse box that controls the AC system?). I had a friend manually charge the system and it works, just not on it's own.

This has been quite the weekend, and I'm not looking foward to trying to figure out what the heck is causing the misfire.. Any recommendations on things to check for either issue?

Just my luck to not get 1...but 2 issues. I never pulled the CEL code prior as I never had an opportunity to really check it when it was on until today, just suprised it was a misfire. I spoke to the dealer before about the CEL light and they believe it was a rich condition prior. I only got like 2-3k miles left on my warranty

Anyhow, this is the end of my rant and long day of wondering what the heck to try/expect, any recommendations welcome.

 

probably a lean condition rather than a rich condition, since the Z has a tendancy to run lean with the mods you have. You may just need new plugs. Does the car have a loppy idle? When does the car throw the code? at idle? under load? high RPMS?

My other suggestion is get a datalogger/code reader and know what's going on with your car. best $200 you will spend. Also, with the mods you have, you should consider yourself lucky if the dealership will look at the car if something goes wrong.

 

Zivman, before I noticed the CEL after cruises that involved lots of WOT throttle runs, etc. Today I noticed the light after starting the car but whe the light was on I didn't know the exact code at the time. But the car did not sound any different at idle. Zivman, regarding the datalogger/code reader, can you recommend a decent brand device?

I'm not quite leaning against a lean condition because i'm at altitude and my tails pipes have vast amount of carbon buildup and the car shoots black smoke sometimes during WOT throttle runs. Oh yeah, and the car reaks of unburnt gas fumes when I get on it.

So to say the time's I've seen the car throw a CEL... under load, high rpms, at idle as well. The only thing that sucks is I cannot say that in the past the car wasn't throwing P0301 codes or just rich codes, but I wanna get a code reader to know what's going on when I see a CEL.

Thank for the suggestion Zivman. As for the dealer, I've got a dealer up the street that knows I'm modified and has been great with servicing my car for warranty work. I've just had lots of warranty work that the warranty provider started sending down an 'inspector'. This last weekend has presented itself with two major issues that I'm gonna have to take the car tomarrow and let them know and hopefully start the troubleshooting process. Today I'm gonna look at the crawford Z plenum and see if I can tell if the PVC system might have a leak or there is a missing seal as in past threads with misfires I read that, that's one place to check.

 

You may not be lean, but I was just stating that most Z's have a tendancy to run lean. If you are concerned, go get a dyno run with a wideband to say for sure where your A/F ratios are. I would also recommend pulling a plug on the bank that the misfire occured and inspect it.

My experience with a misfire code is mainly with a P0300- random misfire. Usually a result of a loppy idle.

In terms of a datalogger, I run a pocketlogger on my Z. I think there may be better ones out there, but I had this for 5 yrs now and it does a good job with the Z. Clears codes, and datalogs all inputs to the ecu via the obdII plug. The software runs on a $40 palm and the info can easily be transfered to you pc for further detailed viewing. There was a thread or two on different software setups for dataloging. I thought digimoto was one that was recommended.

 

do a Compression test and a Leak Down test. My Z did the same thing, but on the #2 cylinder (misfire codes off and on but ran fine) and it turned out to be a bent rod. 2 days before the bent rod was found I put down 252rwhp on the Dyno with the CEL on!!!

 

hey there Chazzg, thanks for the tip, I take it you saw abnormal compression/leakdown on the #2 cylinder? That's a worrysome consideration but i'll check into that asap.

Thanks a lot for the suggestions Zivman, i'm also gonna look into a good datalogger that can pull codes, but hopefully something that's either a device or non-palm based since I don't have one. If I could interface something with a laptop in the car that'd be great. Hrmmm..

 

Most, if not all, datalogger software will work on a laptop so just make your choice.

 

Just a long term update:

Since I got the P0301 code a while back I started filling up with 93 octane and 93 only. Here in CO 91 is the only mainly available gas, but 1 station near my house shells out the gooder stuff. Since I've been running 93 octane. No misfire codes and a little bit better performance, noticeably on warm/hot days. Feels like the car is keeping more timing. It's nice to see no CEL light