Random Misfire...Fresh out of ideas...Please Help!!

[Big Bald]

Well i have replaced o2 sensor, Coil Pack, Plug Wires, Spark Plugs (gapped to .30 NGK BRP7ES). I have no idea what else to check. I looked at my came gears and they are lined up. It started throwing this code after I did my act 2600 install but i rechecked everything i touched during the install. I do not have a 6 bolt so that isn't the question so now i am just looking for suggestions on things i may have over looked. Thanks in advance.....

 

[FASTSPOOLINGST]

what's your fuel set up?

a aftermarket fuel pump like a 255 will cause you to run very rich and at high rpms, this will give you a loud ass backfire.

To fix it, install an aftermarket adjustable fuel pressure regulator to keep the pump from overtaking the stock regulator.

 

[Big Bald]

I figured it out......my lightened Flywheel is causing the issue.

 

[FASTSPOOLINGST]

what the hell would your lightened flywheel have to do with you misfiring. I am running the XACT streetlight flywheel and have never had a problem with that. I also have run a XACT on my other car, a GST and I still never had a misfire as you are describing. There are a lot of people on here that have lightened flywheels and don't have misfires. I think you should research some more and find out the real problem. I'm sure it's fuel related.

I have heard of your car stalling when you push the clutch in at high rpms and let it just fall to idle when having a lightened flywheel, but that's about it, no misfiring.

 

[Big Bald]

I don't have XACT, I have a Fidanza Flywheel....This problem only started after the install of this flywheel. It is not a common problem but it does happen. IT is not fuel related as my setup was perfect before the install. Please let me know if any of this info seems false.

The way the car checks for random misfire: it checks the crank speed. If the crank slows down under a certain power stroke, it assumes that piston is misfiring. The formula used for this is based on a heavy crank/flywheel that will spin at a certain rotational force. Put in a very light flywheel like a Fidanza and the crank can slow down and speed up so quickly that it fools the computer into thinking there is RM. It happens on some cars often, hardly ever on others, and some almost never get a RM code with a Fidanza.

It happened to me when I had my Fidanza put in, luckily I already had DSMlink and could turn off the random misfire check. Without DSMlink, I dont think theres any way around it.

Here are some of the posts on this issue....
http://www.co.dsm.org/vault/list_archive/2002/12/09/005.txt
http://forums.nasioc.com/forums/showthread.php?threadid=392571&goto=nextnewest
http://www.co.dsm.org/vault/list_archive/2002/12/09/007.txt
http://www.automotosports.com/forum/post.asp?method=ReplyQuote&REPLY_ID=574&TOPIC_ID=215&FORUM_ID=4
http://search.yahoo.com/search?p=flywheel+misfire+code&fr=my_top

 

[Rick4g63]

Make sure the Crank sensor is operational and was not disturbed during the installation of the flywheel.

I had a misfiring problem also, THE FIX: one of the wires on the MAF was broken. The wire was broken inside of the wire insulator, so it was hard to physically see it.
While the car was idling like crap, I was making sure the plug wires were in correctly, I also touched the MAF connector and I instanty noticed the idle changed. I narrowed it down to a sharply bent wire on the MAF (green colored wire with a yellow stripe).

Good luck

 

[Big Bald]

I am idling fine. I ony misfire on the highway at cruise. For daily driving in the city, the car never misfires. altho the code stays on. It is almost similar to the 6 bolt swap issue from what i gathered.