Help Please !!!!!! idles & runs rough......I have been getting random misfire codes now for months but having them reset. I called the shop I dealt with on tuning the car and they says it's common on the G35s to set these codes. They didn't offer any help? The codes are coming back on now every 3- 4 days? Any suggestions? I also had a MAF sensor code a while back but it has hot returned.
Not pleased with the NSI experience in N.C. Staff was really good but repairs were not. Thats why I'm here looking for help & they had my car for over a month.

Vortech VQ-2 SC (removed piggy back) using UPREV tuning
Dworks 600cc fuel injectors
Walbro 255 lph fuel pump
Headers, cat back exhaust

 

I have a few questions.
1. Have you checked your valve covers for oil pooling? I ask because excessive pooling can distort the connection between the COP and the spark plug. It's happened to me.
2. Exactly what codes is it throwing?
3. Have you cleaned your MAF before? Have you ever dropped, damaged, or touched the sensor wires? (i.e. during an install) Did you installed the Vortech, or did this shop?
4. Have you ever cleaned your throttle body? If so, did you perform the necessary resets?
5. What shop did you go to?
6. Do you feel the misfires are directly related to your tune?

 

It is not common to have a misfire. Maybe one of your coil packs are loose, that was my problem when #6 randomly misfired a while back.

 

^+1, this is the first place I'd check. Next time you get a misfire code, pull the code (Autozone) and find out which cylinder. Check the corresponding coilpack. A good technique for diagnosing a bad coilpack is to swap it and the opposite one. If your misfire migrates to the other side, you've found your problem.

 

Sorry for the delay. I went to get the codes pulled and the GD light was off. The guy at AutoZone told me the engine light had to be on to read it. I thought the codes gets stored anyways,

Thanks again for all the helpfull advice! I going to check on a few of these things starting with the coil packs since the light has been out for 2 days now.

I was thinking could it have anything to do with when the shop changed my plugs?

I am not really good with cars so i guess I'll look for a coil pack DIY post or vid on the internet.
Wish me luck!

 

I have my car a a shop now and they pulled the codes. they think it may have some tuning issues b/c the car is running rich. but not to direct problem with the misfiring. they said the plug s were way black too.

i'm not sure how the tuning could the culprit if the car ran fine for a year and a half with out a misfire problem?

can this be possible?

also they wanted to look at the cats. Could be blocked they said. would this cause a my problem? I have test pipes i am going to bring them to install and see if it is the problem? IKD what the hell to do. it's just a stupid car why can't anyone i bring it to figure the damn thing out.