Droptopkilla

iTrader: (1)

I have a 2002 Camaro Z28 with a 5.3 that’s having a high idle in drive and reverse. Putting the car in drive it’ll drive itself to well over 30 mph and in reverse it’s the same thing. If I shift into neutral or park after having it in drive or reverse the idle will hang pretty high before it goes down slowly on its own. I’ve checked for cables binding and I don’t see any. I replaced the IAC and TPS. As far as vacuum leaks I’ve plugged every normal hole in every combination I could in an attempt to diagnose but it’s still goes to crazy high idle in drive or reverse and I haven’t been able to find anything by spraying Starting fluid everywhere I can. The tune is stock besides VATS being turned off is tuning a possible issue or what am I missing?

qweedqwag

Did it ever work right, I'm asking to see if it was ever tuned. My the in park idle is set wrong, meaning to high in the tune.

Kawabuggy

iTrader: (1)

You say it idles high in R and D... What about P or N???? Can you post a log of the idle with gear commanded, or current trans gear so that we can see what is happening? Can you post a copy of your tune? What do your RAF numbers look like? Are you sure you don't have a vacuum leak somewhere? I would disconnect the PCV, the power brake booster, and any other non essential vacuum lines and plug them (obviously) just to see if maybe the brake booster is leaking internally, or something else simple.

Droptopkilla

iTrader: (1)

Yes when I got the car I could tell it has been tuned as a lot of CEL’s are disabled but much of the parameters are identical to my other car a 1998 Pontiac Trans AM
Definitely no major vacuum leak as I had expected this entire time unless it’s deep under the intake itself, I had tried plugging the vacuum lines you mentioned and because the exact same thing happened I began suspecting a computer problem. In P or N car sounds great and will idle fine. But putting it into D or R AND THEN going into P or N the RPMs will be high and slowly drop, it’ll sound kinda rough like it’s misfiring slightly and then go back to normal after about 30 seconds. Worst of all the car will work normally for about a minute and then start doing this. Im at work right now but when I get home I’ll post both the Log and Tune

ChopperDoc

A lot of SES (CEL's) lights are disabled by default. It is a master list after all. The only way to know for sure which is to use the "compare" feature and put it against a stock tune, for that make, model, and year. If there are changes, they will have a big green box around them telling you there was a change.

This sounds really more like a throttle blade and/or a tune issue. Here's why: At idle, the IAC controls the air, and has a "learning feature" built in. If you go to: Idle>Airflow>ST Adapt Airflow Max it will state this:

[ECM] 12150 - Idle Adapt Airflow Maximum vs. ECT: Current STIT maximum memory value. STIT will move higher than this to maintain idle speed however, remembered idle value will not exceed this value (eg. if the STIT was 3.44 and the maximum memory value was 2.0, then upon returning to idle in this state the remember value would be 2.0 and the STIT would have to make a quick learn to the previous value of 3.44). This applies to the STIT learned during any of the various PN/Gear/ACon/ACoff states.

Here's what I would do (barring ANYTHING mechanical):

1. Set RAF table to actual "dynamic air" values from a cold start. Desired is what it thinks it needs. Dynamic is what it actually needs.... Just saying.
2. Set IAC counts down to normal range, 40-60 ish at operating temps. 20 is okay for a hot day, 80 is cool for a colder day. Big thing is it should never hit "0."
3. After that, you can adjust the IAC counts themselves, using "desired vs dynamic" on user maths. I have a video on how to do that.
4. Readjust RAF if big changes to effective area were applied, since that affects the RAF (aka desired airflow).
5. Adjust other tables (if needed) like Proportional, Integral, and Derivative (PID). Only reason for this would be hangs or wild swings. With bigger unstable cams, it's actually better to limit these a little bit. Proportional is the main (STIT), Derivative is fast acting (instant corrections and stall save), and Integral is applied AFTER the other two, aka, long term.
6. Drink a beer and celebrate success because idle tuning is normally pretty damn hard to nail down.

I'll tell you though, 99% of idle problems on an IAC car are the TB adjustment screw. Don't count that out, ever.

Stampede4ever

Where should the throttle blade be set at?


Thanks

ChopperDoc

Get the car up to operating temp, then use the IAC counts. You want them between about 40-60 or so at operating temp. The hotter the engine is, the less they will be. Also note, that if you set the RPM too low for the engine to reach, which is possible, the IAC will always end up closing to 0 eventually. This is ALSO a blade adjustment issue, but you'll find closing it more will make the idle potentially unstable. This all revolves around the cam. The bigger the cam, the higher the idle has to be for it to be stable. If it's stock, then simply set it to the range and don't mess with anything else.

To adjust the IAC counts, closing the blade increases the counts, and opening decreases.

If desired air goes way down under dynamic air, even as far as 3 g/s with dynamic reading 15, the blade is too far open, and the PCM is trying to reach the idle RPM goal but cant. That's all that really means. Normally it won't have too many problems reaching the "desired goal" if it is above dynamic. However, you might end up with hangs, surging, and "cruise control" as you explained.