Im trying to help out my step bro with his 4g I have a 3G but when idling his car will miss really heavy it will drop around 2-3 hundred rpms what could cause that

 

Ask your stepbrother to check for trouble codes. It could be dirty or broken IACV, dirty TB or MAF. Test your TPS and ignition coils, and replace spark plugs. But scan for trouble codes to find what is causing this because there are a lot of things that could cause rough idle.

There are also other threads dealing with rough idle, those could help you out

 

Well he had it scanned and it was saying a coil pack was bad but don't know which one

 

Wouldn't a bad coil pack cause misfire? That should give you at least one trouble code from P0301 to P0306, which tells you which cylinder is misfiring.

But you can use a multimeter/ohmmeter or an oscilloscope to check your ignition coils. Do you have either one to test them out?

 

He took it to Nissan and and they couldn't tell which one it was they don't know what there do in haha but I don't have either of them

 

Take it to autozone for a free trouble code scan. That should show you what's wrong or which cylinder is misfiring. If money's not a problem you can always buy 6 new ignition coils to replace your old ones. 4th gen coils are known for their below average durability.

 

Average durability you say huh? Obviously you are a noob for saying such a comment. Better do your homework before coming on here with those accusations.

OP, if your check engine light is not on and it is misfiring, start disconnecting your coils one at a time and see which one doesn't make a change.

 

Yeah, wasn't it the 5th gens having coil pack issues? Not heard too much bad about the 4th g

 

Woah chill man. I have actually read threads that discuss the coil problems of the 4th gen. Iwas just trying to help him out since no one else was. You didn't have to call me out that way.

But hey lkoroush I hope your stepbrother gets his problem fixed soon !

 

agreed!! For most 4th gens with hanshin Coils they are quite reliable...i do believe 99s have a different story for some reason with them going sooner....however i replaced them on my 95 just after 150,000 mi....id say thats pretty reliable even if u spend the full 600 a set for new ones....

whatever you do DONT BUY EBAY/CHINESE COILS!!!!! cant stress it enough!!! maximas are finicky about their coils and i bought a set for 120 from hong kong off eghey because the price was right....however they were going out after 5000 miles!

Best advice, hit a junk yard and pull 8 coils....even IF you get 2 bad ones you still have 2 to play with....if not, keep em as backups or sell em....i got mine for $10 a piece at the pick and pull....

 

See the highlighted post below. Only that year was affected and Nissan replaced them. My original Mitsubishi's from my 95 last just under 300K before random misfiring.