24x people, please help...

[capss9c1]

Hello all. I have been doing a lot of reading and research on this great forum and would like to ask for some help i did a 24x conversion on my caprice and been trying to figure something out. If i start my car cold and let it warm up it seems to idle ok, once to operating temp the iac shows 80-90 and the car will stumble when i put her into drive and struggle to hold an idle, if i shut the car off for a few seconds then restart the iac goes down to 40-60 and will not stumble into gear anymore. This is driving me nuts. Also does the dynamic airflow and desired airflow have to be the same? I read a few posts about this and there seems to be conflicts about this right now my raf at op temp is about 7.40 gps and if i adjust the iac effective area to make the desired and dynamic even it makes the raf go up to 9.50 or so. I have the ve and maf tuned at idle and cruise at +- 2% ltft. I also read that the effective area should not be touched unless using different iac motors. Im using a 2002 fbody auto calibration and i believe my iac on my 58mm tb has way different iac circuits than a stock tb on a fbody. Thanks in advance. Jim

[AdsoYo]

The fact that it behaves fine after restarting the car warm has me baffled. Have you tried the 2001-2002 Chevy Express files? The 350 Vortec is more similar to an LT1 than the LS1 is.

[capss9c1]

Should i try the express van iac files only? I was thinking of that but that motor too has a 70mm or so throttle body. Also thinking of using the express van knock sensor files since im using the 97 fbody sensors. This is starting to discourage me.

[AdsoYo]

Tell me about it. I've been trying to dial in my t/a since September. In my experience everything takes a ton of trial and error. I'd try the van setup, then if that doesn't work start tweaking cell values until the IAC behaves like it's supposed to. I'm still messing with mine every now and then so LOTS of trial and error.

I also have a 96-97 fbody knock sensor and it doesn't work for me. I get max knock retard at all times. Someone on another forum said you need the correct sensor for the PCM, not just any obd2 sensor. Now I have a 2001-2002 Express sensor waiting to go in and we'll see what happens. Are you having that problem?

[capss9c1]

I have not been getting and knock retard at all. I checked the resistance of the fbody and the express sensors and they are very close. im gonna put the express knock sensor tables into the fbody calibration and try that since the knock sensors are in 2 different areas. thing is when I restart the car and it runs good it has pleanty of power and idles great. ve and maf are almost dead on. just the restart issue is killing me. wonder if the dynamic and desired airflow tables not matching have anything to do with it.

[AdsoYo]

I would always have 0 knock retard also. Then I changed detection mode from 'cylinder' to 'engine' and I had max knock retard all the time. I'll keep thinking about the restart issue but right now I don't know. Hopefully someone else chimes in.

[capss9c1]

Did you ever correct the knock sensor issue? i put all the gains and table from the express calibration because it is the same type knock sensor and block as the LT1. im also correcting a few spark items. what about any of the iac tables? should i change the park position values or effective area since the LT1 and LS1 TBs are different? Im thinking this is my issue. i just cant figure out what in the calibration will effect warm restart with the idle. Strange.....Thank for the help

[AdsoYo]

I just set the sensor back to 'cylinder' to disable it again. In the spring when I do oil, clutch fluid, power steering, and some other stuff, I'll replace the sensor with the Express sensor. I changed the IAC reset position and effective area to max at 255 since that's what stock LT1 fbody IAC counts max at and didn't notice any difference. I have a manual trans though so maybe things behave differently for me.

[capss9c1]

I just went thru my complete tune and changed a bunch of stuff, the open loop table was commanding 11.1 afr at cold start and staying rich along the way. i leaned out the whole table, changed some spark, and a few other things. AdsoYo, what do you have for timing? VE table? thanks

[AdsoYo]

Yes 11.1 is pretty rich unless you live somewhere that's currently 10* outside. So your car is running richer than the open loop table is commanding? Maybe there is something in your tune that's not quite dialed in causing that? Anyway here's my VE and spark tables. I feel pretty good about the VE table. It is the result of many hours of logging and adjusting. It was between 30-40 degrees on those days so I was shooting for histogram values between -8 and -10. The spark table's general shape is based off an old thread I ran across where Russ K posted a picture of his table. Then I tuned the idle and cruise cells for maximum vacuum, set WOT to 34*, and blended the table.

383LT1VEtable.png
383LT1sparktable.png
383LT1sparkgraph.png

[DrLoch]

Post your tune, a number of people that have done this swap may pipe in with some advice. Who's 58MM TB are you using?

Also check your TPS value. Mine hangs once and a while and will show 1-2% with my foot off the throttle, if I blip the throttle it will go back to zero. Mine is a Holley 58MM, I need to look in the TB to see which blade is not lining up correctly.

[JasonS5555]

Hey Jim,

I'm also 24X in a '96 SS Camaro M6. I also have a different issue, but it may be related. I get a tip - in bog / stall behavior that I can't seem to shake. Its worse cold than hot. Also have a 58mm TB, BBK I think. It does hang at 1% occasionally as well.

I can't figure out a way to tune the TB iac area, and I don't know if the iac motor in the LT1 style TB will go up as high as the LS1 style TB. You can't command enough counts in the bi directional control due to a number of bytes restriction.

http://www.hptuners.com/forum/showth...-for-IAC-motor

I also started a post for those of us with 24x conversions:

http://www.hptuners.com/forum/showth...se-step-inside

Any thoughts would be welcome,

Jason

[capss9c1]

Adsoyo, 11.1 is what the stock ls1 table was commanding and i was getting exactly that i did some research and learned the lt1 wants a lot less fuel than that.

Drloch, im using a Holley 58mm tb to correct my split fuel trims. Also the Holley is a lot more responsive to the iac tuning than the bbk was.

Iac stuff im still trying to figure out. Seems to run strong at operating temps while still having the dynamic much larger than the desired airflow. Still no comments on that one?

[capss9c1]

Drloch, my friend had the same problem with his bbk tb, drilling a small hole in the iac passage cured his hanging problem

[JasonS5555]

Have you looked at this post?

http://www.hptuners.com/forum/showth...nd-MAF-Airflow

Is your airflow discrepancy at steady throttle?

Where did he put the hole? In the IAC or butterfly?

Thanks,
Jason