yellowbird

my car is a 02 t. a. mods,as follows: 224/224 cam,headers,gears,slp air Induction,2800 stall,and a JANZER T.B.here is my problem,had all these mods done at livernois motor sports and tuned there.they could never get it to idle that good so i took it to HARDCORE MOTOR SPORTS about a month ago and they did help it alot,one of the problems they said they found was in the JANZER T. B.the air hole was epoxed over so the cleaned that out ,but im still getting that surging,it seems to do it more when its warmed up,like after i shut it of for awhile and start it,I will put it in gear and it wants to do that romping thing,like last night i was going thru a fast food place and had to wait awhile in line so i put it nuatral and it started to surge up and down for about 30 seconds and then it leaveled out,other then that the car runs great,do you think the problem is in the t.b.or somthing else.i really need some help here, this is really getting to be a pain in the ####.!! thanks.

DrkPhx

iTrader: (15)

Based on the comments above, it almost sounds like your fan settings. What are the fan "ON" temps set at? Some tuners like to turn Fan # 2 too early which causes the fans to constantly cycle ON. This in turn will draw an extra load on the engine causing surging because of decreased airflow at idle. So then you need to compensate by increasing the "Fan IAC Correction". The factory settings are really low, so expect to add some flow by going up incremently until the surging goes away. Note: Don't add too much, just enough to get ride of the problem.

technical

Does the IAC plunger move smoothly through the bore? If there was epoxy stuck in there, it may be hanging up causing the PCM to have a hard time dialing in the idle.

Technoman64

iTrader: (6)

I deal with the same issue with a TR224,112* seperation cam and have a Stock throttle body. I have improved it some using EFILive FlashScan and tweaking things. I am still learning though so I do not have the correct answer to this question. I do know exactly what you are talking about though.
Mine is a manual and will only do this after it has warmed up and is sits for just a few minutes and I re-start the engine. Idle goes up and down for a bit(20-30 seconds) and then levels out at my set idle RPM.
I beleive it has to do with the way the factory ECM determines the proper idle control. The way GM did it is not a simple method but rather complex using several pieces of information and many methods to control the idle. They use timing adjustments to control the idle as well as fuel and air adjustments.

98 Raptor TA

iTrader: (9)

I have a 224/224 cam and my ta does the same thing, only when the fans come on. Once they turn off, it smooths out. Then they come back on and it starts that up and down **** again. I'm gonna take it to my tuner next week and see if he can up my "Fan IAC Correction" airflow. but i'm also gonna check what technical said, i do have epoxy in that IAC bore so it may make the plunger not move so freely. That's funny how we all have 224/224 cams.

98redorangeta

iTrader: (10)

Yellowbird Does this only seem to happen when you change it from one gear selection to the next like park to reverse on drive to nutral? If so it may not be a fan issue.

technical

I have a TR224/112 also, but no surging problems. I fixed all of that through tuning. I have a M6 though.

Technoman64, I had some issues with idle and rough off idle on a warm restart. The commanded fuel in open loop table needed some adjustment. Since you start out in OL no matter how warm the car is, it was commanding too much fuel. After 30 seconds or so (now in CL) the idle would settle down. Just some food for thought.

SSpdDmon

iTrader: (10)

Once your desired airflow and IAC counts are in line, try changing the spark modifiers (overspeed/underspeed). To get my friend's Torquer cam to idle, I ended up taking about a half of a degree out of the cells filled in. I also took about 20~50% out of the direct airflow correction table. The logic behind this is, the cammed engine is a much free-er reving, free-er breathing machine. It doesn't need as steep of a correction as the stock setup did. That's why it's surging. It's over-correcting itself. Play with those tables and you'll see it smooth out.

technical

Those tables are key. I had to reduce the settings quite a bit. It would put the PCM into a "rebounding" cycle if the idle dropped too far...constantly over correcting.

Technoman64

iTrader: (6)

Thanks for the info!