Help with Idle/Startup issue/tune

[LS3RX7]

So I am helping a co-worker that has the following setp:

2001 5.3L with cable throttle
P59 from 2003 with the blue and green connectors
Running a XR269HR Comp Cams 269/273 .525/.532 114LSA
243 Heads
MAF sitting behind a cone filter and in a 4" Aluminum pipe

I have flashed in a 2003 Chevy Express 6L cal as it had the right HW IO's for the ECU and cable throttle. We are having an issue when we start it and try to idle. The engine wants to run up to 1500rpm or so and slowly walk up. I have made the following cal changes:

1) Made the P101 fail criteria 150 to get it out of the way

2) Set the rpm disable for VE to 200 to force it to run off the MAF

3) Told it it was a 800 (truck) platform

4) Changed cylinder discplacement to match 5.3 and said it was a 5.3L

5) Set fans up

6) Co-worker took some out of the VE surface at lower load/rpms

The issue we saw when we first fired it up was it would run at 1500-2000rpm. This was before I made it run off the MAF. Once it runs off the MAF, it will idle at 800 as is the desired idle speed, but then when the IAC closes (goes to 0), the engine speed goes up to 1500-2000rpm. We cannot figure out what is causing the engine speed to increase to such a high value?????? Different attempts have it idle at 800 for different amounts of time, then it will go up again. I know the Idle Airflow isn't properly set yet, but it is hard to do when I can't get it to idle at the desired idle speed.

I can post up the cal and log when I get home today, but was curious if anyone else has had this happen or know what to check.

Thanks,
Scott

3)

[WS6FirebirdTA00]

Sounds like there is a hole in the TB blade that is too big or the blade isn't fully closed.

[LS3RX7]

I thought that could be an issue, but it seems weird to me that when the IAC closes, the idle jumps up. You would think when the IAC closes, the idle would drop, no?

It seems the rpm jumps when the timing goes up, which might be when it is coming out of Cat Lightoff. All the additional timing causes the engine speed to increase, but I don't know how to pull that down....confused.

I would have thought having the large cam would just make the idle 'hunt' around desired, not flair up and stay high....

[WS6FirebirdTA00]

Depending on what mode it is in. Probably also going off some different tables, airflow adders, timing or something. Post the tune and log and that will help.

[LS3RX7]

So attached is the cal, some log files, and my config file....

[WS6FirebirdTA00]

Need to get the fueling in line. It happens when you go in closed loop and the fuel trims dump in fuel.

[83scramber]

Ok, I will give a shot here too. LS3RX7 is helping me tune my car. I double checked the entire intake air system and intake for leaks using car cleaner..... nothing. If I push the throttle closed by hand the idle will drop and randomly flair to 1200-1500 rpm. I have read and searched through all the based tuning info on this site (all very good info). It seems like this ting runs really poor for the size cam I am running.

The data attached above was running only MAF based airflow. In the past we modified the ve surface taking our ~20% in the idle region trying the adjust the fueling. This made the idle far worse than just running off the maf. I cant believe I need to reduce the ve by more than 20% at 800 rpm for this cam. Is there anything else I should try?

My next thoughts were to modify the spark in the idle region (I can take out any more air). Reduce the gains in the idle Pid controller by .5X..... it seems to me like the idle controller does not like the choppy idle of the cam==> let the cam idle where it likes not where the stock tune thinks it should.

Any other input would be welcome here. If i get this stable enough to run at idle I think we can tune it from the info found through searching.

Tim

[LS3RX7]

I tried to setup a histogram to be MAF (Hz) as the axis, and then populate fuel trim in the cells so that I can tune the MAF. I cannot get the histogram to work though. I added MAF (Hz) to the table, but when I go to make the histogram (in #8), it only give 1 cell and not the full MAF curve. I figured I would be able to make this then if I could get the idle down around 800, I could tune the maf with this histogram. I was even going to tune the maf in the higher airflows/frequencies by disabling PE and just not beating on it....

Since I can't do that, I guess I am forced to look at the frequency I was at before it went closed loop and modify the maf curve accordingly by the LTFTs

[83scramber]

Ok so after another couple days of screwing with the tune I have made no progress. I have done everything from fixing spark to 8 degrees to fixing fuel to stoic..... I still end up in a condition where the speed increases to 1500-2000 rpm and hangs there. I have read every section and post on idle tuning and tuning in general using HP tuners and am not a novice tuner.

After looking into the sensors and controls I decided to pull the IAC and check it for proper function. I noticed when commanded to move it doesn't. I checked the wiring harness i am using and its all pinned out correct (using the GM wiring diagram checked 3x). The IAC seems to be about half way open and stuck there. I assume this is causing the extra air torque causing my high idle speed.

My question, has anyone ever seen the controls side for the IAC fail in the controller/pcm? I know the harness pins out right.

I am running an older (2002) engine using 2003+ express van drive by cable harness and pcm (i got the harness for free). Has anyone here attempted converting from DBW to cable throttle and had similar issues? If you have done the conversion, what is the part numbers on your PCM?

Tim

[83scramber]

I'll answer my own question here. The controller I have does not have the drivers for the iac for idle control. The tps works and software flashes and reports changes in iac posistion but without the correct hardware io no actuator movement.

To summarize, green and blue post 2003 controllers are capable of running drive by cable only if the iac related hardware is installed in the circuit board. This can be determined one of two ways. Remove the cover from the controller and look at the board, if the upper most circuit has pins comming through the board it can support dbc. Or by service number, ask for an express van ecu, truck ecu don't always have the hardware. See attached for more info.
http://www.lt1swap.com/cable_conversion.htm

Is there any way to flash this ecu without using more
Credits? I can use the other and have already licensed the ecu?

[MMGT1]

no there isn't unfortunately. You must have licence over the ecu you are flashing to

[RACINGVORTEC5.3]

What you can do to stay with that pcm is manualy calibrate the IAC motor The motor will go up and down with a twist.You may have to take the TB on and off a few times .......sorry didnt see your thread sooner I went trough the same trouble a while back

[vette_c6]

have u got a wideband ?
your car looks way need to be get fuel adjust
i have fixed your Config
you can have a look at the config log any on of your tunes and load all data
have a look

you cannot confirm that you have a problem ,, and you havent tuned your car yet

have a look at enjoy it