Would a cam with 46* of overlap be enough to cause the rough idle issues covered in the stickies that are resolved by changing the idle O2 swing points? I have almost all of my BLMsbetween 124 and 133, but at idle it eases up to 137 or more, and in just a few seconds of idle. Sometimes it idles smooth and others it shake and vibrates, and I can't tell what is going on.

 

I would suggest not allowing the engine to idle CL. I believe my bin has a OL idle or CL idle flag to check or uncheck. Maybe yours is different. Check your mask. I believe you will then use the coolant based tables to determine the commanded A/F. I believe you are MAF based so your situation is different than mine.

 

No, not MAF. I switched to MAP with a 730 $8D and painless wiring kit, and it does stay in closed loop at idle. I have the same 12-268-4 comp cam with 224/230 @ .050.

 

OK. Then you may want to run OL idle and limit invoke of CL > 5 mph.

 

I ran a cam with 54* overlap in C/L. Idled fine at 800rpm. You need to adjust the O2 voltages for Rich/Lean/Mean at idle. Check out posts by Traxion on the subject.

 

That is the article in question. Is a cam with 45* of overlap big enough to cause the problems documented there, or should I be looking for something else?? I can start the car and take a short cruise, and have no problems. If I drive to the next town in my area 9 miles away to go to the bank when I idle at a stop light it's very rough until is sits idling for a while, then it smooths out, but if I don't wait and just turn it off in the parking lot as soon as I stop, when I start it back it idles rough again and is very jerky on mild throttle.

 

You'll probably want to look at the proportional gain. Read up on articles by RBob. Takes a bit for idea of PID controls to sink in, but that's what really makes the diff in achieving a smooth idle with bigger cams, altho your cam isn't all that big.

 

Hey Ronny, how do you invoke CL >5mph? I've been trying to figure that out for the longest time.

 

I dont have access to my lappy here at office but I thought the EBL xdf had a MPH trigger-constant to allow CL ? Maybe your mask does not? I bet it can be added? sorry I cant help on that. When I used to use $42 Tunercat was helpfull in adding much of that if I asked. I heard about things here and got back to them.

 

I found a constant called IDLE Open loop RPM Threshold (S_V4 only) CL Qual. That's probably it. Sorry didn't mean HIJACK the thread.

 

In EBL, there is a flag for open loop idle (Option Word 1 - Bit 2 - OpIdl), then a scalar for when to enter idle (Idle - MPH Threshold)

 

Graeb. thanks I have not looked at xdf since November. Do you think it appears in other GM masks?