I always used regular in my car, never had any problems. The way it started running about a month ago, it seemed as if there wasn't enough air going into the engine, it sounded almost like it was choking. The more gas you gave while driving, the lower the rpms would dip. Very weird indeed. Then one day, the local Shell was out of reguler, so they were selling premium for the same price. Filled up and BAM problem gone. Next time I filled up with regular, no problems. A couple more tanks, and the same problem. Went to a different gas station, filled up with premium, and problem gone! What the hell could the problem be with my car? I'm sick of buying premium gas, since I go through like 4 tanks a week for work. Help!

 

Guessing... Carbon buildup has raised the compression. Ping detector is backing the engine off.

You have done all the other obvious things. Filters, sparks, injectors, ect I assume.

 

I have. Anything I can do about the carbon crap other than rebuild?

 

I would think that you could clean the piston tops and such without rebuilding. I don't know this, I am only guessing because I had a 2 stroke bike I used to have to scrape carbon from it frequently. If the valve train is also dirty you would have to look into that, too. I would think even with cleaning carbon from the pistons, there would still be some carbon in the ring grooves. Just what I think.

 

Run some seafoam through your vacuum system, it helps take the carbon buildup out.

 

Through the vacuum system? Could the problem be all the trans oil in my vacuum lines then? I have yet to replace that vacuum modulator.