I've been having a rough idle lately and it has been getting slightly worse. I bumped my idle up to 900 on my PFC and it isn't as prevalent, but for about a minute after a warm startup it is still there. Mods are listed in my signature. Here's what i know:

Stock motor, 68,000 miles. Power is as good as ever, and boost is strong at 11-8-12.

I have an exhaust leak from the twins to the downpipe. I have tried a few times, with new gaskets, and can't get a good seal. I understand that i might need to have both machined to get a seal. Not sure its relevance to my shitty idle.

Just installed new spark plugs no more than 1000 miles ago.

I have replaced a good amount of vacuum lines, and know that poor idle can be a factor of a vacuum leak.

I haven't experienced break up before, so don't know if that's what i'm getting, but unloaded at constant throttle (whether it be idling or 3000rpm) I am getting what feels/sounds like a misfire or slight hesitation which causes the motor to shake slightly.

I have not done a compression test yet, because i don't have the rig.

Anyone had similar symptoms or any ideas towards diagnosing my shitty idle?? Thanks

 

check your plug wires. before you changed the plugs did you have this problem?. the exhaust leak could be causing most of your idle issues.

Jeff

 

DEF check you ignition...i had the same problem, im looking into investing in an ignition system ( the hks ) when i do i'll give you my results. but def get new plugs and wires, that fixed my idle problem

 

I have new plug wires and have been waiting for time off work to throw them on. ill change the plugs again, while i'm in there too. Also looking into some thicker copper gasket material for the downpipe as a temporary fix until i get my single kit next month. Any of this make you guys lean towards engine/seal failure?

 

Your symptoms sound like a vacuum leak or, possibly, a leaky injector. Ignition problems should be more prevalent under heavy load. At 3K RPM I would not suspect apex seal damage to cause a misfire.

Are you using the O2 sensor? If so, how old is it? That could affect light load mixture and possibly cause misfires.

 

I figure my motor would still be fine since it runs great at all rpm greater than 1000. Yes, I am using the stock O2 sensor. I didn't think much about it... I'm due for a wideband anyway. I have no experience in leaking injectors. I am going to buy new injectors next month along with a gt35r kit, so if that is the issue hopefully that'll take care of it. probably take care of a lot of potential vacuum leaks as well I've had vacuum leaks and boost leaks and this idle of mine doesn't seem like either...