Surging when coming to a stop

[minytrker]

I have a surge only when coming up to a stop, it will surge about 4 times then idle perfect at 800rpm. What should I check first, RAFIG, timing?

[Tordne]

RAFIG gets my vote. Also perhaps the Throttle Follower decay rate might be too quick.

[98SS2836]

Or you may need to do an idle relearn. You should do one after every flash. Not that i do cuz i don't.

[Tordne]

I believe all the learned data is toasted after a flash anyway so the idle learn should not be required.. I've never done one since I started tuning.

[minytrker]

If I thorw the car into neutral while driving the rpms will drop and stop at 800rpms perfect. Its just coming to a stop with the clutch in and in gear.

[TAQuickness]

when do you get the surge? Imediately after going into neutral (clutch in or physical neutral)? or as the vehicles approaches a stop?

AFAIK, learned idle is preserved thru a calibration flash, and wiped on a full flash. Either way, it's a safe bet you'll need to go thru idle learn procedures if you are making changes to idle.

[SSpdDmon]

I've been working out idle issues for the last week on mine. I think one positive change I made was to zero out the first 3 rows of the Learned Airflow table (Idle>Learning). With a cam'd car, the natural idle of the cam jumps around a little more than stock. I think the learned desired airflow has a way of sliding around with the stock settings...kind of like the effect lazy NBO2's have on the fuel trims. By doing this, you widen the acceptable range for idle rpm variation before it tries to learn the desired airflow away from where it needs to be. The only side effect is, you might idle a hair higher or lower than your desired idle (depending on how big your acceptable range is).

http://forum.efilive.com/attachment.php?attachmentid=1014&d=1160860324

You'll also have to keep an eye on your base spark tables. On a manual, I usually set them equal to each other. If you log a short period that includes just idle and a few revs in neutral, you can see the path the spark will take as it drops. It might be slightly to the right of this path on the road as the throttle cracker may be active. Timing will cause slight variations in idle where less timing will cause the motor to drop faster and more timing will do just the opposite.

Chances are though, your issue lies in the Desired Airflow Tables and the tables that contribute to the IAC's involvement (3 airflow tables under learning). On cam'd cars, I've found the extremes of these tables over compensate, which causes the surging. See the post on the 224/228 tuning. Tweaking these tables can take a few passes at the least. But, I'm getting some good results with taking a little out here and there (mostly around the 200+rpm areas).

[minytrker]

I noticed last night that when the car is cold it wont do it. After the car all the way warm it starts, plus it seems a little better when its cool outside.