Hi all,

Right as my stock 09 Cobalt SS crossed 85k miles, the car started having an issue where it would misfire only on cold starts and make an even louder ticking noise than the DI. Once warm, the car stops misfiring, gets good gas mileage, and does not feel down on power. I did let the car go to 4k on AMSoil OE and PurolatorBOSS filter. There was some gas in the oil, but figured that was from the misfiring...

After researching, I went to my local GM dealership and picked up both the Intake/Exhaust Actuators. After changing my oil, I installed the new actuators and disconnected/reconnected the battery. Car started up just fine, no misfires!

Fast forward the next day, and the same P0011/P0014/P0300. Now I have tried:

• Replacing the battery (it was low on voltage)
• Installed OEM ACDELCO Coilpacks
• Installed ACDELCO Iridium plugs (made sure they were gapped .035)
• Put a reservation in for a 2023 Acura Integra (6mt)

I also purchased an ACDELCO camshaft position sensor and am planning to install that this weekend. Anybody know what I can check next or had this exact same issue?

 

I could be wrong, but pretty sure the gapping needs to be 0.032 for the spark plugs because of the tight tolerances (and tempermentalness) of this platform.

 

Just checked, they’re gapped to .032” not .035”… my bad. Still having issues

 

The misfires are potentially related to the intake runners being coked up from oil blowby.

The intake exhaust actuator replacement normally takes care of the P0011 & P0014.

Do you have the RPD or another method to see what your fuel trims are doing or what the wideband reading is doing

 

I have a PLX Kiwi and use dash command. I think I could pull the fuel trims. Do you know what the measurement is called on the RPD or Wideband? Are you just looking for A/F?

 

A/F for wideband, I don't know what the RPD calls fuel trims. But there should be a STFT and a LTFT in the PLX Kiwi system

 

Cool, just found them. Will go cold start the car and pull this data!

 

So when the car was running like **** this is what I see:

Commanded A/F: 15.1
LTFT: 8.6%
STFT: 0%
fuel level input: 27.5%

 

See how the car runs with the maf unplugged, just at idle no need to drive around. With the LTFT being at 8.6% it points to a potential leak in the charge piping.

 

I take it LTFT is basically commanding more fuel to make up for the leak then?

Also, have you heard of a leaking charge pipe that is ok under boost when warm? Car doesn’t misfire or loose power when warm.

 

When the car is cold the car is in open loop, so the fueling is significantly off which could cause the misfires. Once the car reaches operating temperature the car switches to closed loop and the STFT starts making the needed adjustments.

It could also be a wideband sensor going out on you for the misfires.

The cam actuator solenoids still throwing a code is strange to me, when you removed the old ones did you see any material on the oil screens? Also, I know this is a stupid question but I have to check, you didn't get the plugs backward for the solenoids and the grey one in the front of the car?

 

I just replaced the after-cat o2 sensor a month before this issue happened, but did not replace the primary o2.

When I removed the old shitty one that was installed on the car, the top screen on the exhaust actuator was completely off… I did flush the oil with AMSOil OE and PuralatorBOSS filter when doing the change.

Also, black tipped actuator closest towards the firewall and grey tipped closest towards intake…


Destroyed actuator

New actuators

 

Ok,they're installed correctly and connections don't look crossed. You might want to remove and inspect the new ones just to see if more junk got caught in the screen, you can clean it off with carb/maf cleaner and reinstall.

Couple other questions from the pictures
1. I see a K&N intake, when was the last time you cleaned the filter and MAF?
2. I see the MAF wiring indicating the wiring was replaced at one point, I would check the wiring to be sure there is no corrosion at the connection point
3. The PVC line into the intake barb looks like the clip is broken, is the fitting lose on the barb? That could be a source of a small leak that would cause cold start issues but smooth out once going to closed loop, also it wouldn't impact your ability to make boost.

 

I’ll give that a go tonight! Agreed on how strange that I’m still getting the cam codes… would not oiling the top gasket cause an issue? Maybe I forgot to do that.

1. Never on both… I do have a new drop in K&N filter and can clean the MAF.

2. I never replaced the wiring, but the previous owner may have? I bought the car with 30k miles back in 2017. It has 85k now.

3. I haven’t messed with anything in the bay, in quite some time but maybe I hit a pothole and it came loose. Will check!

Other things to note are:

A. I do have an OTTP downpipe
B. The car is on stock tune / never been tuned before.
c. Car is at 85k miles.

 

Depending on the miles on the filter that could be causing some issues, certainly change the filter and clean the MAF.

The mods with the tune can be adding to the idle struggles, but it shouldn't have a significant impact if the filter is oriented correctly. I forget the orientation, but there is a thread around here about the K&N intake and filter rotation.

The wires to the MAF being white indicates it's been replaced, the one from the factory is color coded. The GM replacement pigtail is all white wires, so the previous owner probably had some issues with the MAF and it was replaced.

 

Going to dive in now, wish me luck!

 

So… K&N intake was disconnected at turbo inlet / hanging on by a thread.

Also, exhaust solenoid had grime on it so cleaned that off.

Started the car up and the LTFT is 0, but now STFT is fluctuating like crazy. Haven’t cycled the PCM, should I do so?

 

The STFT do fluctuate around a bit, if you clear the codes with your scanner it will reset the fuel trims. I'd give it sometime to settle out before being to worried about the STFT moving around.

 

It felt like it was misfiring but not sure… since it wasn’t a cold start.

 

Cold started the car this morning and sure enough, random cylinder misfire and Exhaust Camshaft Position (CMP) System Performance codes came back…

 

After three weeks of driving, I was driving some backroads up north Wisconsin and noticed oil all over the driveway when I got back to my friends house. The Oil Pressure Sensor switch went bad. After replacing that, another oil change, and two weeks of driving, the misfire has seemingly went away and has not comeback. STFT and LTFT are now normal. Dont know if the Oil Pressure Sensor or new oil fixed the misfire?

Hope this thread helps anyone that may have this same issue.