P0300 error code after hard acceleration

[addictedtoguitars]

Last week, I was driving in Sport Mode at around 100km/h when someone started tailgating me and flashing. I stepped on the gas and easily reached between 160 to 170 km/h, before slowing down.

Everything was fine for a few kms, even with stop-and-go traffic, until I downshift two gears before facing a corner, while driving on open road at 100/120 km/h.

After a few minutes, I stopped at a traffic lights and changed to D mode. As soon as I started moving, I felt a loss of power/shuddering, CEL started flashing and misfiring started. Since I was arriving at the office I thought that was something temporary and that everything would be fine in the afternoon.

Unfortunately, once I started the car in the afternoon, misfiring was still present, CEL was on and I struggled to exit the underground parking.

The car was towed to a garage and I was told that P0300 error code was present. They've been trying to identify the reason for misfire without success and they mentioned that misfire is only observed until normal temperature is reached and that some vibration is felt in the engine, but it's not due to engine mounts, since both engine mounts and transmission mounts were replaced 10000 kms ago.

Since the mileage is around 107000 kms and spark plugs were never replaced, I told them to replace them but it didn't solve the issue and CEL is still on. Besides replacing spark plugs, MAF was cleaned, harness were checked and catalytic converter but all is fine.

A few months ago, I had CEL, stabilitrack and abs lights turned other the same scenario: riding at 100km/h and hard acceleration, but at the time the lights went off as soon as I restarted the car.

May last year, the car was overheating and it was solved after replacing water pump, thermostat, a pipe and something else that I don't remember.

The guys at the garage are running out of options, but they mentioned that they would perform some O2 tests. They won't to avoid going guess mode and start replacing parts, like high pressure fuel pump, but it might get costly without solving the issue.

I went through a few threads but I didn't find any for the same scenario that led to the misfire and CEL on.

They are suggesting to replace the MAF to see if it solves the issue, before providing them the go ahead, I did a few searches to try to find the expected readings for MAF, without success. Any ideas?

Does anyone have any suggestions to share with the garage that might help them troubleshooting this issue?

[bsn]

Check coils and wires.

[addictedtoguitars]

Originally Posted by bsn

Check coils and wires.

Like swapping coils between cylinders to check if misfire moves to different cylinders?

[gtstorey]

Originally Posted by addictedtoguitars

Like swapping coils between cylinders to check if misfire moves to different cylinders?

Are you getting misfires showing on particular cylinders? Or just the random/multiple misfire code?

[addictedtoguitars]

Originally Posted by gtstorey

Are you getting misfires showing on particular cylinders? Or just the random/multiple misfire code?

I was told that it’s just random misfire errors

[gtstorey]

Can't move stuff and see if it follows on a random error.

I would start with fuel delivery, but that is a guess without data to go on.

[addictedtoguitars]

Originally Posted by gtstorey

Can't move stuff and see if it follows on a random error.

I would start with fuel delivery, but that is a guess without data to go on.

Can you tell which data should be checked to troubleshoot fuel delivery?

[gtstorey]

Need to be checking all the data to try and determine the cause. But you can start with fuel trims.

[addictedtoguitars]

Today, I went to the garage to pick my car, since they ran out of options. As soon as I drove the car for 50m, I went back because it was misfiring like crazy. I could even notice the rpm going up and down.

Since the fuel tank was almost full, I thought that when I went to refill the tank, they could have gone for 91RON instead of 95RON - here in Qatar, that's all we have - which might be causing misfiring.

While I was trying to convince the guy to drain the fuel tank and fill it up with 95RON, he told that we should go for a ride while he was collecting some data with the OBD scanner. While I was driving, he was telling me that some injectors were shutting off and MAF readings were quite strange.

We went back to the garage, he told to turn off the engine and turn it back, but I couldn't turn it back because it was showing signs of dead battery and, all of a sudden, alternator was showing 0v and Battery Saver Active was showing at the dashboard. He decided to check that battery status and when he asked me to turn on the engine, the battery was reading 4v.
We tried a new battery and the engine seemed to be running fine.
Battery Saver Active appeared back in October last year, but it disappeared once I restarted the car.

When I drop the car, I told them that I was hearing some whining sounds when I turn on the car in the morning, that seemed to that was coming from the alternator.

Long story short, they will be check the alternator and they will also try to recharge the battery to confirm is the battery is dead or not. The battery was bought in November 2021 but due to the extreme weather we have here in Qatar, we are lucky if a battery last this long.

Hopefully, everything will be fine after checking/repair/replace the alternator and replace/recharge the battery.

Cross your fingers, like I'll do. I'll keep you posted.

[bsn]

These cars don't like low voltage.

[addictedtoguitars]

Problem solved after repairing the alternator.
Thanks for your tips.