m1mmmm

Hi Everybody - Driving a short distance tonight and when I got back home noticed CEL on, checked with reader and it says Code P0300. Two nights ago I was stopped at a red light and the car died, first time ever for that, restarted easily and no problem until CEL tonight. I cleared the code tonight and restarted the car a couple of times and no CEL light. However I did not drive the car.

The only deviation from my regular routine was after hurricane Harvey we had a run on gas here in Dallas for a few days with none available but I had a full tank of premium unleaded already so no problem. However, I used that gas and then for a few days the only gasoline available was regular unleaded, I filled my tank one time with that grade and noticed the car idled just ever so slightly rougher but that was the only issue at that time. I have since filled the tank again this time with my regular premium grade gasoline (finally available) and the car died once a couple of nights ago at a light but easily restarted and then the CEL light Code P0300 came on tonight. Since the last fill of premium gas the idle has been very smooth. Any thoughts on what is going on?

I’m the guy that had my car in the shop for several months because it just would not start one day...the post was “replaced fuel pump now rear SAM is bad...”. I replaced several parts then and it turned out to be the ECU. The car has run fine since then until this issue. I think this is the first ever CEL the car has thrown. None ever came on with the Fuel pump/Rear SAM/ECU fiasco. Again, any thoughts on what might be going on would be appreciated. Mike.

Yidney

Man, you are not having the best luck. A tank of regular gas will not cause it. As you have probably Googled, P0300 can be several things. Have you tried scanning with something other than a generic OBDII scanner?

m1mmmm

Hi Yidney - I searched here but didn't find much with just the P0300 code alone coming up, it was always included with several other codes in the previous posts, but like you said it could be several things. I have only scanned with my generic scanner so far and got the lone code. I did drive the car last night after I cleared the code, went on the highway got up to around 70 mph, went maybe five miles, ran fine and CEL light did not come back on. The one time it died at the light it happened without the car shaking, in fact I didn't even realize it had happened it was that smooth. Then the engine started immediately with no hesitation. As you can tell I'm a little gun shy regarding this car after the fuel pump/rear SAM/ECU incident. I drove it to the office this morning, so far so good. I'm up to around 55,000 miles, it recently passed its annual inspection with no problems and has been starting and running normally since the ECU and other parts were replaced. The plugs were replaced about 1000 miles ago, one-year old battery, all services up to date. Tires, brakes, suspension parts all new, still has the original spark plug wires and coil packs I'm pretty sure. It was at the shop for so many months and had several service people trying to diagnose the previous intermittent not-starting problem who knows what happened to it. Not starting at home is one thing, but shutting off in traffic at a light is something else.

Rayvan

Replace the spark-plugs before anything if they've got a bunch of miles on them, just to eliminate the cheap fix.

m1mmmm

Hi Rayvan - The spark plugs were replaced about 1000 miles ago during routine maintenance so I’m pretty sure I’m out of luck on that cheap fix, but thanks for the tip. Mike

m1mmmm

So far so good, no more CEL's, engine stopping, or rough idle. Hopefully it was just a temporary glitch. (Knock on wood/head, lol.)