please need help with slight rough idle!!!!

[3134]

I changed my spark plugs from denso iridiums to ngk bpr7es spark plugs and gapped them at .030. The denso's were gapped at like .032 and when i took them out the car idle'd fine. Then when i replaced them with the ngk's the car wouldn't sit at a steady idle, it goes one notch up and down inbetween 0 and 1000 rpm. It is slight, but i can see it is rough through my safc and also the tach moves as i said before very slightly. I have driven it and it still won't go away. It has been doing it for a full day and shows no signs of letting up. Please, does anyone know why this is happening???!

 

[bluetlr2001]

Try adjusting your biss. Since you put in a colder plug its not firing as hot as it did with the denso. That may take care of your problem. Also try cleaning out your throllte body while your at it. Ill go ahead and post a thread to adjust your biss if your not familiar with it.
http://www.vfaq.com/index-main.html

It talks about using a scantool but you can just listen to the idle and get it pretty good.
Good luck!

 

[3134]

ok, well just to let you know when i put the old plugs in the problem still is happening... I thought it would go away once i put the old ones in since the problem only occurred when I put the new plugs in

 

[bluetlr2001]

Did you check your plug wires to make sure they havent crapped out on you. YOu also may want to try adjusting your afc at idle!

 

[3134]

what do u mean adjusting my afc at idle? What i did which seemed to work was i messed with my biss and now my safc shows a nice smooth idle but still the tach is slightly (less than before) moving, is that ok???? why is my safc saying i have a smooth idle but my tach isn't so smooth?

 

[bluetlr2001]

Are you referring to your factory tach the tack read out on the afc. If your referring tho your factoy tach they are never accurate. As far as i was saying about adjusting your afc was cahnging your lo throttle at 1000rpms which will change your idle. But normally you will have some movement on the tach because they want set at a perfect idle the whole time. As long as your not getting a bad surge then your ok. And if its still idleing lower than before move the biss out a little more to idle it up

 

[3134]

it's idling at the right place, but the stock tach was slightly jumping but not more than a millimeter at the most. Once I adjusted the biss the car seems to idle smoother and my safc screen shows a steady smooth line that does not jump or anything. Does that mean my car is running fine?

 

[bluetlr2001]

It sounds good from what I can understand. The factory tach will normally move some so dont worry about that. Its almost impossible to get a tach to not bounce around because everything makes the ecu keep changing while the motor makes its revolutions. Itll change due to the temp and your fans turnign on and anything electrical changing will affect it.

 

[3134]

ok that is what i thought until i went into my mom's bvmw which is stick and it idle's so smooth which made my tach moving seem like it was horrible. I guess having a bmw in the driveway makes me realize how rough of a ride my car really is