Before I do something drastic......ie pull the motor back apart. I thought I would see what you guys think of this issue.
I changed....
New Cam: 229/240 .631/.610 117 LSA
Old Cam: 224/232 .600/.600 114LSA
New Lifters: Rhoads Vmax
Old Lifters: Rhoads Standard
Rockers: T&D Old setup and new.
Springs: Kmotion-K800
Engine is a 403 9.25:1 SCR, AFR Custom CNC 235CC heads, JBA shorty headers 2.5" magnaflow catback. Currently no cats installed.
Issue-
I have been through just about every "idle tune" sticky and thread I can find. Played with the PE trick to lean out idle. tried every timing advance from 18* to 33*. Used VCM controls to try and find the "sweet spot" by playing with the AFR, turning off spark Idle, STIT off, reset fuel trims....etc.
No matter what I do, I can't get rid of the Idle hunting and surging. Now I have only played with idle RPMs between 850-1000, but I didn't think this cam would need any more than that?????
One of the advantages and or disadvantages of the rhoads vmax is to in theory be able to "tame" larger cams. I went this route in the hopes I could get this cam past the smog police here in Cali. I have thus far tried .030 lash and .010 lash. At .030 I had approx 16" of vacuum, at .010 I have about 12"-14" of vacuum. In either case the car does the same thing....surges and shudders.
I have sprayed the intake looking for vacuum leaks, no changes apparent. I used a infrared thermal temp gun on my headers, so significant differences in temp pointing to a specific cylinder.
Attached is the latest tune, with this attempt I simply went back to the OEM timing tables knowing I would be playing with the VCM controls. Also attached is the russK idle scan.
I am assuming I am in "open loop", but I don't understand why if STIT is turned off in open loop, why am I getting such large swings of STIT on the scanner, even hitting fuel trim reset on the VCM controls does not seem to affect it????
This engine with the "old cam" ran great, idled near stock, decent mileage and put down 650RWHP at 5500 RPM, one of the reasons I changed it out was trying to get my last 75HP I felt I was missing as HP peaked 1000 RPM early....theory was I was out of cam given my CI Now the car runs terrible, stinks to high heaven, my eyes burn when it idles in the garage for more than a couple minutes....Unless someone can point me in a different direction, I am about to put the thing back up on blocks and change the cam back to my old one......
Up through frame 6014 I haven't touched a thing. Starting at 6014 I make changes using the VCM controls.