Hello everyone, please take a moment to read, I'm sorry for the lengthiness but I'm making sure to give as much detail as possible. I have a 2015 LTZ 1.4 Turbo with 123k miles. I recently had to replace my valve cover in late November 2019 and since then I've had a misfire with CEL code P0300 (Random misfire Detected). Heres a few details of the valve cover replacement. When I went to take the coil pack out during the replacement process, one of the spark plugs was covered in oil. The boot for that hole was also in bad shape so I did end up replacing all 4 spark plugs (ACDelco 41-121) and also a new coil pack (ACDelco D521C). Other than that the valve cover replacement went smoothly, I followed all the directions from a thread on here and put it all back together. After that I noticed I had a slight misfire. It started off lightly, only noticed when I would climb hills or under load 4-5k rpm. Withing the next day or so I could feel it while lightly driving down the street under light load of around (2-3k rpm/15-20mph). It got bad enough over the next few days after the replacement of the valve cover it started throwing P0300 and I stopped driving the car and had it towed to a home mechanic. I did a compression test before having the car towed and all 4 cylinders held between 175-180. I must mention before the valve cover replacement I was never experiencing any misfiring issues.
The mechanic was stumped and also couldnt figure out the reasoning behind the misfire. I was also having the P0299 code (Underboost) and had him replace my turbo, hoping that was a reason behind the misfire, no luck it was still misfiring. Had the throttle body cleaned, no luck so I just replaced with a new one, still misfiring. The only thing that made a difference and stopped the misfiring/jerking was unplugging the Mass Airflow Sensor. When he did that it would drive with no jerking but the engine fan would stay on and the car would run at about half the normal operating temperature. So logically I assumed it was just a bad MAF sensor and went to buy a new one. OEM MAF sensor (Bosch) same as the one that came out, plugged it in and still misfiring.
I'm at a loss, I'm pretty stumped and my car hasnt been driven for over a month now. I'm tired of throwing money at it and I'm trying to avoid the costly price of taking it to the dealership. I'm not sure if I messed anything up during the valve cover replacement but I made sure to stay very vigilant while doing and noticed no red flags. Any advice would be helpful and I'll do my best to recollect if any questions are asked.
Link to Valve Cover I bought:
SCITOO Engine Valve Cover with Gasket Replacement for Buick Encore Abarth Volt Chevrolet Cruze Sonic Cadillac ELR 2011-2017 Valve Cover Gasket Set https://www.amazon.com/dp/B07L4NCPYS/ref=cm_sw_r_cp_apa_i_JGGjEb3BM5H3V
Link to the Turbo I bought:
www.am-autoparts.com
The mechanic was stumped and also couldnt figure out the reasoning behind the misfire. I was also having the P0299 code (Underboost) and had him replace my turbo, hoping that was a reason behind the misfire, no luck it was still misfiring. Had the throttle body cleaned, no luck so I just replaced with a new one, still misfiring. The only thing that made a difference and stopped the misfiring/jerking was unplugging the Mass Airflow Sensor. When he did that it would drive with no jerking but the engine fan would stay on and the car would run at about half the normal operating temperature. So logically I assumed it was just a bad MAF sensor and went to buy a new one. OEM MAF sensor (Bosch) same as the one that came out, plugged it in and still misfiring.
I'm at a loss, I'm pretty stumped and my car hasnt been driven for over a month now. I'm tired of throwing money at it and I'm trying to avoid the costly price of taking it to the dealership. I'm not sure if I messed anything up during the valve cover replacement but I made sure to stay very vigilant while doing and noticed no red flags. Any advice would be helpful and I'll do my best to recollect if any questions are asked.
Link to Valve Cover I bought:
SCITOO Engine Valve Cover with Gasket Replacement for Buick Encore Abarth Volt Chevrolet Cruze Sonic Cadillac ELR 2011-2017 Valve Cover Gasket Set https://www.amazon.com/dp/B07L4NCPYS/ref=cm_sw_r_cp_apa_i_JGGjEb3BM5H3V
Link to the Turbo I bought:
Chevrolet Buick Turbocharger with Exhaust Manifold Dorman OE Solutions - AM-4248448138 at AM Autoparts
Buy Chevrolet Buick Turbocharger with Exhaust Manifold Dorman OE Solutions - AM-4248448138 now at AM-AutoParts! Always Free Shipping. Order today by 4 P.M. EST and your order ships same day.
www.am-autoparts.com
