Please forgive me if I'm posting in the wrong place. I'm in desperate need though. I purchased a 2003 G35 a few weeks back. It ran fine no issues we (my husband and myself) replaced valve covers, spark plugs, 1 coil, oil change, changed tranny fluid, have replaced a few air hoses and i believe that's all. We are now having a hard shift from 2nd to 3rd gear and a rough idle. The only code we pick up is P0300. Took it to a dealer they only found a hole in the air intake (accordin looking) hose, we replaced that still have same issues. Any words of advice would be wonderful. As we are sending our daughter off to college in this car, well if we get it running properly. If not she will be driving my 1998 mini van that has over 280,000 miles. Thanks in advance

 

p0300 is a misfire code. make sure all the plug wires are connect to the correct cylinder. also check to see if all the spark plugs fire. esp in the 1 cylinder you changed the coil.

the hard shifting could be from the fluid change. make sure there is the proper amount of fluid in the trans. and be sure to use the OEM fluid matic S or J. (one of them got discontinued i forget which one) how many miles are on the car?

 

Thank you for your response. This morning we replaced the pcv valve and put in a new battery. Car has 178,000 miles. We used trans fluid from auto parts store that said it was compatible with matic j, would you recommend purchasing matic j from dealer? Or do you think we are okay with the compatible brand from auto store?

 

I would use J matic only.

 

ya like eaz said i would only use the OEM matic J fluid. i have heard the aftermarket fluids can cause issues.

is the rough idle resolved after the PCV?

 

Matic J was replaced by Matic S but either will work fine.

 

I dealt with a similar thing in my 03 Sedan, hard shifting/slipping between 2nd and 3rd. Turned out to be the TCM. Don't want to get you worried, but it's a possibility.