Hey all. I have an 03 G35 Sedan 5AT and just installed the plenum spacer (z1) as well as some spark plugs (NGK Lasers). It appears to have a rough idle. During the installs, I noticed some carbon build up in the intake. I have heard of people seafoaming but I have also heard (and searched here) that on higher mileage motors (I have 180k) it could hurt things. What do you all recommend? I did the removal of the negative battery cable but the idle is still acting like theres a MAF issue. Idled fine before changing the plugs, gaskets and adding plenum spacer. Thanks in advance.

 

Probably just need to perform an idle air reset since you've changed the volume and flow. Wouldn't hurt to hose down the MAF with MAF cleaner.

http://nicoclub.com/archives/g35-350...procedure.html

 

Update. The rear bolts on the plenum cover was not torqued enough. Its handled now. No need for resets due to no codes. I will take it for a test drive in the am. Appreciate the response Cleric. Any advice on the carbon build up and cleaning method? The Seafoam method seems to be split and I saw a reference to a dealer cleaning option. What are your thoughts? Or anyone else for that matter.

 

I popped the throttle body off, unplugged it, sprayed some brake clean on a paper towel, and went to town. Once the valve was clean I also taped everything up and painted the top of the TB black to match my intake. I had read that you can damage the throttle body by moving the valve with your hand (which I didn't believe), and that if you do move the valve manually you'll have to go through the throttle position relearn procedure, but I had zero issues after bolting it back up.

 

I'll give that a go and see how things run afterwards, tnx.