P0300 Code with high Idle
 

Recently my 370 threw a P0300 code. My cars about 11 years old so I figured I needed new spark plugs or coils. I proceeded to buy new coils and plugs and cleared the code but then the code came back the next day. After looking on the forum a little somebody suggested to clean the throttle body’s so I did, cleared the code, and then it came back. A little side note the only thing i’ve done to this car is install a Tomei catback exhaust ( I know it’s basic ) and replace plugs and coils. I’ve still not found the root to this P0300 code. Any help please?

Check all your air intake clamps. It sounds like you may have a vacuum leak.
You can also clean your MAF sensors.

I did check to see if I had a vacuum leak but i didn’t catch anything wrong there, I will double check and also clean my MAF sensors.

Unfortunately, that is a catchall code that can be difficult to troubleshoot. Sometimes it's just some random sensor that failed. Good luck with your troubleshooting.

Yeah man it’s been a difficult process so far trying to troubleshoot everything, I only have 44,000 miles so I didn’t expect this but it’s been a headache.

I've had the exact same problem as you ever since a few days after getting a few mods installed and getting an ecutek tune at Z1. Car made amazing power on the Dyno (for the mods) and made the 5 hour drive home like an absolute peach. Threw the code about 3 days later on the first cool morning I left for work. Idled rough, power was lacking.

I did get mine to throw a P0305 one time (misfire cylinder 5).

Mine seems to have improved since I got the ecutek dongle and accompanying iPhone app. It ran an update the first time I connected them. Plus I cleared all the codes with it. I also tried getting gas at a different place (Shell, I usually use Exxon) and I put in a bottle of the Chevron fuel injector cleaner stuff on my last fill up.

Something I also noticed in my particular case was the problem seemed to kinda get better when my fuel level dropped below a half tank. Maybe in my head but it's something I think I've noticed.

I'm still trying to figure out mine as well, though I'm hopeful at the moment it's gone away or fixed. Keep in mind it could also be fueling ie: bad gas or a failing fuel pump or bad fuel injector. I've also wondered if maybe the fuel sending unit could play a part.

But please, for the sake of all that is holy, update this thread when you find the problem. There's way too many abandoned P0300 threads on this damn forum...I will certainly update mine, even though I've pretty much been talking to myself in there the last few days lol.

Did you or your tuner see anything on the datalog when the car threw the code?

I just sent Z1 a datalog this past Wednesday, which is when the dongle came in. So I'm still waiting to hear back from them. Though we've had a dialogue going the last few weeks.

I personally don't know what to look for in the live data. Though since I have the dongle I keep the app open and am ready to start recording at any time anything funny happens. But like I said it's been doing really well ever since.

Oh yeah something else I did when I got the dongle was the throttle body relearn, which is normally a PITA but is made easy with the dongle/app. Just press a button lol.

In the app I also see what appears to be an option to turn the fuel pump off....is this a feature you would use to possibly purge fuel from the lines so you don't make a huge fuel mess if say you wanted to change a fuel injector or something like that?

I used that to (turn pump on without starting car) run my fuel pump to circulate fuel to check for leaks after installing new fuel system. Great feature.

I was doing some thinking and I really only have an exhaust as a mod. Anyone think the code will come on from the air being more dense then when it’s warm out? Just thinking because when it was warm out I never had this issue and it did start when it started getting colder.

So my engine light turned off. I replaced my spark plugs and coils, cleaned throttle bodies, and cleaned my maf sensors. I cleared the code after replacing the spark plugs and coils and it came back, i also cleared the code after cleaning my throttle bodies and it came back, but i didn’t have time to clear the code after I cleaned my maf sensors but after driving for a few days the engine light turned off today. I’m not sure if the code just turned off randomly or if any of this helped but I will update if the same code comes back on.

Well a day passed and the engine light is back on, it’s a lot colder today though so may be the more dense air.

Yeah brother our Zs don't seem to like cold weather. I would invest in a good OBD2 reader with live data and stuff that can actually run a misfire report and tell you which cylinders are misfiring.

Does the car feel hesitant when giving it throttle? I dunno man sometimes I feel like these cars just don't like weather changes. I've been dealing with the exact problem as you and mine seems to have just gotten better on its own. Mine hasn't thrown the code in almost two weeks now, even though it does pop up sometimes in the ecutek app. Then it'll clear on its own.

I do know the P0300 code is a useless pain in the *** that causes people more anxiety about their car than actually providing any useful information.