Good evening,

Well, my CEL light came on at lunch and my CarChipEX captured all the data (love that thing). At any rate, the light has remained on, so it is definitely going to the dealer.

There are two things I need to know:
1. Does the information below tell you anything about what might be wrong?

CarChip Data
Trouble code: P0300
Trouble description: Random/Multiple cylinder misfire
Coolant temp: 174.2 f
Engine speed: 675 RPM
Short-term fuel trim (bank 1): 6.25%
Short-term fuel trim (bank 2): 16.41%
Long-term fuel trim (bank 1): 9.38%
Long-term fuel trim (bank 2): 9.38%

2. Lets say the service guy says "well, your light is not on now" or "we could not find anything". What questions do I ask to make sure they did a thurough investigation? For example, "did you check the spark plugs" or "did you check the fuel quality", etc.

One last note, the gas in my tank was loaded up on Monday and it is Sunoco 93 octane. Also, mods are listed in my signature (nothing big).

Thanks for any help.

 

There was a thread recently that discussed this is relation to timing controllers. Do you have one?

 

Here is the thread https://my350z.com/forum/showthread....threadid=58782

 

No timing controller, but not need for one. I am not running anything that would require timing alteration. Aside from exhaust, pulley and intake, I am pretty much stock. If I was running boost, I certainly would have a timing controller. However, I will read the thread. Thanks.

Jeff@Performance and Jason@Performance, I could use your help here.

Anyone else have suggestions?

 

Well, that thread was a waste. Those guys were fighting like crazy! Oh well, still good information (at least the first half), but it doesn't help with this. Argh!

 

According to the service manual, PO300 is the code for "multi cylinder misfire". There are a ton of things that can cause it......things that can cause it and the things the mechanic should check are listed on pages 291 to 296 of the electronic service manual I have. On the chart shown, things that can cause the PO300 error code are:

-Improper spark plug

-Insufficient compression

-Incorrect fuel pressure

-Injector circuit is open or shorted

-Fuel injectors

-Intake air leak

-Ignition signal circuit open or shorted

-Lack of fuel

-Signal plate

-Heated Oxygen Sensor 1

-Incorrect PCV Hose connection

--------------------------------------------------------------

Hope this helps, at least you know what should be checked now.

 

peptidbond

Was it Raining? Sleet?

Cheers Amy -

 

My 2 cents worth: Have the dealership clear the code and see if it ever happens again. Have you changed to colder plugs by chance?

 

I'll go check with one on my master tech's when they get in this morning.. but only because he's going to ask.... approx how many mile on the car since you installed the Injen CAI and the light came on?

 

Perhaps you did not install the MAF properly or it was damaged durring installation. Dirt can make a maf angry too, make sure your air filter is in working order. A vacume leak after the maf could cause a problem, but if your idleing low you probably don't have a leak. Check your plugs. See if they are fouled out. How many miles do you have? Your z should still be under warranty, right? It may be a pain to take it in, but at least you won't have to pay.

 

Checked with my tech today and was told this is a common problem with cars when adding a CAI. It's very hit and miss if a light/CEL will be triggered. He also said it should only happen once or twice and usually doesn't come back. They have no answer for why it does this either. Sorry we're no more help than this, but we're just going by our past experience.

 

Wedge - Thanks for the info. That will certainly help.

Amy - No rain or sleet, which is amazing considering the weather lately.

mjedens - I will clear the code using my CarChip and see if it comes back. This morning, it was gone. But sure enough, just like yesterday it came back at lunch.

Jeff@Performance - The Injen has been on for many many many miles. Something like 10,000 miles. I never had an issue such as this after the Injen install. I have had the CEL come on before (once at the track and once just driving), but that was long ago.

etx - More good info, thanks. The injen isn't new, so it might be a dirty air filter. All my hoses going to the from the Injen are nice and tight, but I will check them. I guess I should do a quick look over. As for the plugs, I will leave that to the dealer. I could do them, but that is what the warranty is for. And yes, I have plenty warranty time left.

Jeff@Performance - Thanks for asking anyhow. I am going to give the engine a look over and then take it in.

As a quick side note, I really think I got a bad tank of gas. This seems to have happened within a day of the new gas. I might be wrong, but it would not surprise me.

 

Hmmmmm..........it sounds like if you quit eating lunch you won't have the problem anymore

 

It could be from the UR pulley. I am not a 350Z expert, but other OBD2 cars sometimes have random misfire errors pop up from stuff like lightweight flywheels. How much lighter is the UR pulley than the stocker?

On some other cars, the ecu uses the cam angle sensors and crank angle sensor to determine if a misfire has occured, taking weight off the crank's rotating mass via a light flywheel or pulley can sometimes make it throw that error.

Or you just might have a fouled plug...

 

By the way, if you are being prompted for a login to www.digitalharbors.com, that is my sig. Something has gone wrong with my web hosting. I will drop the image hosted there and call my hosting company now. Sorry folks.

By the way, NEVER EVER USE WAZOO WEB FOR HOSTING. SUXOR!!!

 

It happened to me about 3 times after the injen intake. I just went over 100 miles an hour and went away. I Guess all the air flow helped the ecu figure it out. I thas not come on in over 3 months.