all of a sudden car runs like total ****

[G35-31]

mmm i just swaped my non rev motor for the REV UP motor and now my idle when i start up jumps by its self to 2k and then goes down between 1k and 1200 when i get on it car feels like theres something holding it back but i get the same thing, power while crusing it stutters i can get off the gas and the idle will stay there at rpm's

[385thumper]

Thanks for quick reply. I'll pull some plugs and read them. I just find it hard to believe that plugs can take a dive that quick unless they crack. The only thing I changed was fuel. It ran strong when I parked it.Now in one start up it acts up. Every time I kill it and start it while it's screwing up, problem goes away.

[385thumper]

OK changed plugs the originals were worn and looked bad. Gap checked .056!
Still have stumbling problem. Everything looked great. I have not checked coils. My instinct tells me bad gas. How can something run good-go bad-then good again. When water gets in fuel it floats around in a bubble. Maybe thats the issue. This car under the hood and every where else looks and feels untouched. I just broke a cherry by changing plugs. Just to let you know I'm not exactly a novice. I have a '92 camaro I've built ground up for road racing with 485 hp and 500 ftlb torque. I'm thinking keep it simple stupid. FYI 63000 miles on G35.

[EncoreCestMoi]

your code points to multi cylinder misfire. I still think it is ignition related. If you are convinced of bad gas run it out and refill with premium and dump a bottle of octane boost in for good measure.

Also when you do that disconnect the neg battery cable and let it sit for a couple hours. it will clear the code and reset the ecu. after I replaced my gasket and had the battery disconnected while I did it it ran a little rough after everything was back together. I initially thought I hadn't fixed it but then it occured to me that the ecu had to relearn. After about 25 miles everything smoothed out and the idle is low and steady.