B4 anyone roasts me please know I have been searching as many threads as possible for 2 days.

I just bought the car from INFINITEABYSS 3 -4 weeks ago...2003 350z APS sT w/UTEc on a non-built motor.

I am getting the P03011 and P03012 codes for a misfire on the 1st and 2nd cylinder. HOWEVER, no rough idle and no noticible loss in power. I live in San Antonio, TX and it has been in the 80's. On Monday a cold front came in and Tuesday early morning and Wednesday early morning the temperature was in the 50's...SUDDENLY, no CEL.

I am 98% certain the plugs need to be replaced because of the mileage on the motor and I will be replacing them Friday. Okada coils are <30 days away. UtEC map selctor set cool days, hot days, track days

Question is: TOO RICH for outside daily temperatures, timing issue, or am I totally off? Suggestions for a tuning shop in San Antonio, TX.

 

Random misfire is going to be part of your life now so just accept it. Mine only happen on cold start and maybe one every month or so. Every FI'd car should have an OBDII reader so you can just erase it.

 

+1 I have had these codes from the first crank on my FI set up

 

HKS makes an ignition amplifier that may help misfires.

http://www.intensepower.com/hkstwpodliii.html

 

if you have an individual cylinder misfire, you should try checking and changing the plugs first. if not that, it could be coil.

an individual cylinder misfire usually means there is some problem. the random misfire code P0300 is no big deal, though.

BTW, do you ever see your Check Engine Light flash while you are WOT? it flashes when you have a specific cylinder misfire. I had an issue with cylinder 5 when I have TN ST on my car. Every since going greddy TT, the issue went away. My CEL would flash when I was in the upper rpms of a 5th gear WOT run.

 

There has been no evidence provided that the HKS unit will eliminate the misfire codes associated with the UTEC.

 

Does detonation cause misfire codes? (sorry if slightly O/T; just curious if that may be a heat and/or hot spot related event in the cylinder)

 

Hmmmm... It worked for Stormcrow on a GreddyTT.... Maybe someone could pm him for further details.

 

Did it? I haven't read any confirmations, just people threads about people who spent $500+ for it and had the same CELs.

 

Looks like you may be right. It worked for a little while, but then he eventually got the code again...

https://my350z.com/forum/showpost.ph...7&postcount=40
https://my350z.com/forum/showpost.ph...7&postcount=79
https://my350z.com/forum/showpost.ph...8&postcount=84
https://my350z.com/forum/showpost.ph...3&postcount=89

 

Kevin,

did you ever get around to installing your other UTEC to see if it is a UTEC issue.

It could be a UTEC issue, but I am more inclined to think it has to do with the the lasrger injectors not working as well at idle conditions along with cooler sparkplugs.

I think the majority of the misfires come at startup and idle. People have said that if they run 2 steps colder plugs, they get a huge number of misfires at starup.

 

No, I haven't installed the 2nd UTEC. Can't seem to find the time, and its starting to get cold here.....

 

come on.....it is only about 1/2 an hour to swap it out inthe G.

 

Yeah, a 1/2 hour for the actual swap and then 1.5 hours to get the dash to fit perfect back together!

 

My codes were for cylinders 1 and 2...they were not random. I spoke to Shariff and we agreed t ostart with the plugs and then look at the coils. We agreed it "likely" was not the injectors or plugs because they were replaced back when the turbo went in. I got my 1 step colder plugs 2 days ago. I put them in yesterday at noon and then reset the CEL. No codes after driving all over the city last night and early this morning. I have not opened her up to WOT. Inspection of the plugs showed a white residue around the electrode and carbon around the ceeramic base. I took an OHM meter to the coils...each coil has 3 tabs...mine are numbered 1 2 3
Resistance Coil #1 Coil #2
1 / 2 0 0
1 / 3 8.5 8.5
2 / 3 7.5 7.5

I am going to follow up and see if my other coils have similar variances or if they have a closer resistance reading to each other. This may be the issue.