Code P0300 after CBE install
 

Hi all,

I'm posting here as well as on the FI exhaust thread for some feedback. This morning (cold, rainy) the Z threw a SES light, 3 days after I installed the Fast Intentions cat back. I bought a scanner, and code P0300 came up (random/multiple cylinder misfire). The car is running fine, although the idle is at 1100 rpms. I erased the code, and it did not re-appear after one start up.

Any thoughts what could cause this? I want to make sure I didn't do something to trigger this while doing the exhaust install before taking it to the dealer (car has 6000 miles on it).

The only other mod on the car is K&N drop-in filters.

Thanks!:tiphat:

Did you try resetting the ECU? It could potentially have just been the ECU adjusting to the CBE however the misfire is a bit strange as I doubt a CBE would ever cause it to misfire.

No, I didn't try to ECU reset procedure. I wondered about the ECU learning phase, too.

UPDATE: Idle is now normal (about 800 rpms)

Sounds like the ECU was adjusting the fuel trims, if it doesn't come back I am sure it was just a hiccup while the ECU was adjusting.

Update - Same Code Again
 

OK, so a fwe weeks after clearing the P0300 (random/multiple cylinder misfire) the MIL came on again this morning. The conditions were almost identical to the first time (temps in the 40's, damp after overnight rain).

This time I did not clear the code. I have an oil change appt. at a dealership I've heard is Z and mod friendly (I haven't owned the car long enough to have been to any dealership) in 2 weeks, and want to see if the MIL goes off on its own. The idle speed is up (1000 - 1100 rpms), which, from what I've read, is often related to a vacuum leak when this code is thrown.

Here is my dilemma: Do I leave the light on and have the dealership service dept. address it (with the slight chance they may blame tampering with the EVAP canister - the cover was removed and a line heat wrapped as part of the FI exhaust install), or just clear it again (the idle returned to normal when I cleared the code last time).

I'm open to any thought you guys might have :tiphat:

leave the code and hope it isn't because of he evap system, also don't mention knowing anything about it if they do just say you had it installed at a reputable shop and you just noticed you had a light on you don't even know what the light means.

Thanks 1slow. Right now the light is off (went off after about 5 drive cycles). Sounds like the best idea is pretend it never happened.

Huh?

Well as someone else says, play dumb, see what happens.

Any other mods?

Moisture getting into a coilpack that might be bad (although if so, it's strange you didn't get a specific cyl miss code -- not to mention a new car...)

Wait -- evap cover removed??? Not sure what you are talking about, but if not sealed right could be causing a vac leak. That would give you a lean misfire.

Jordo, I wondered about moisture getting into something. I've had EGR valves go bad on other cars in wet weather, but will consider the coilpack, too.

The evap canister cover (rear p-side of the car) has to be removed for the Fast Intentions right muffler to fit. The cover isn't sealed, it's just there to add protection to the lines. Since I did not get a P01XX code (which is where the EVAP specific codes live, I believe), I didn't think this was the cause. But I'm paranoid about having warranty work denied because of mods.

The only other mod I have are K&N drop in filters. They've been installed for 3 months (2 months ahead of the exhaust install) and had no problems.

Given that no specific cylinder was identified wit hthe random miss code, I'm thinking there's a vacuum leak somewhere. Your other symptoms corroborate that, although I have no idea why it's affected by wet weather.

You could try spraying cab cleaner around the engine bay and see if the idel changes...