Working on my idle a little bit and I wsa just wondering what everyone is running for timing at closed TPS. right now I have 27 degrees and I think I am going to try 34 or so. As it is if I sit at a light for a while the car will start to surge, acts like its going to die and then revs back up. I am hoping to smooth this out and perhaps get my idle a little lower as well to make it sound meaner.

 

My camshaft 224/230 605/622

Closed TPS #'s
0 rpms 12*
400 24*
800 24*
1200 26*

Car is an M6 and idles very smooth at 800 rpms.

 

lear, My LT4 Hot Cam is 210/228 112 lsa .525/.525 I'm running 32* 400-800, 34* 800-1200 I tried quite a few different settings to keep the AFGS as low as possible. I don't have a converter (yet) so getting the A4 smoothed out in gear is a little harder than an M6 in neutral. I like to keep idle down to 750 D to hold it back at stop lites with only one foot on brake. There is also another table in the OBD1 settings, not sure if your OBD2 has it. It's called Idle underspeed spark advance, you could tweak a few degrees there to see if adding more underspeed recovery timing helps the idle hold RPMs.

 

Is the a/c on when this happens? Where are your iac counts when idling warmed up?

 

It's worse with the a/c on but still there without it. My opti just died so this issue is on hold for now. It was one of the cheap ebay optis so maybe that was it's problem all along. I will pick up on this issue after my new delco opti gets here. Hopefully I can install it this weekend. One thing I did find is something is causing the PCM to pull a few degrees of timing at idle, not sure what that is yet. if you just touch the gas the knock retard goes away. My idle MAP is 55kpa, seems kinda high for 850rpm.

 

Ok, new opti, runs much better now all over but I still want a better idle. AFGS is 9-10, 55kpa, 45 IAC, still seeing 1-2 degrees of knock retard at 0%tps. Anything over 0% and it goes away instantly. Is this just the PCM pulling timing to try to hold RPM ? I am going to try more timing and lower the idle a bit if I have free time at the shop today.

 

Also I am reading this data realtime with a snap-on red brick if it matters.

 

you shouldnt have any knock retard at idle. your RR's might be making some noise at idle whats your lash set at and what is your idle oil pressure?

 

Raised timing to 32@400 34@800 34@1200, dropped RPM to 800. AFGS went to 8ish, 50kpa, 40 IAC, sounds better due to the lower idle I think, still surges when not in P or N though not as bad. Also zeroed the EGR spark retard table out, I think this is why was seeing the retard at 0% TPS. I see none now. I still think 50 is too high of a MAP at idle. What's normal for a cam of this size?

 

As an FYI, I run 42 degrees at idle at 1000 rpm and about 58 Kpa vac on my cam. This advance was decide upon after hours of testing and the best vacuum was achieved. If you up the idle rpm, you will get better vacuum. Nothing wrong with 50 Kpa if the car runs well.

 

I have plenty of vacuum for the brakes, But it doesn't run well. I need to get rid of this surging. If I set the idle to 1000 it would certainly be gone but with an auto thats a bit high.

 

Have you confirmed no vac leaks?

 

pretty certain my rockers are adjusted right, I have oil pressure, no vac leaks, etc. It's a tuning issue. Not mechanical.