I'm running EFI Connections 24x conversion on my '89 IROC. The engine is a Dart 421 ci,AFR 227 heads,Superam intake,52mm TB,Procharger D1SC.
Everything has been fine,just having issues with the IAC (well,we think we've narrowed it down to that) Idle will hang up to 1500 to 2000 rpm,then eventually drop down,can flair up again just sitting idling.While driving it can hang the rpm up at times (basically take your foot off the gas & keeps going,very slow to come back down)
Has no vacuum leaks (other wise it would do it all the time) Where I get it tuned,we have tried to get it fixed or at least better with the tune,but still has issues.
I work at a GM dealer & we have discussed this & think that it may be the difference's in how the LS1 PCM sends current to an LS1 IAC versus an L98 IAC. The drivers in the PCM may not be strong enough/send enough current to work the L98 IAC properly. Just a guess at this point but have to try something.
Looked for after market IAC's, only found a remote IAC from Jegs,not sure if it would work.
EFI connection has the electronic TB but my harness from them was not built for that so I believe that's out.I will contact them anyway for there opinion.
I doubt anyone's run into this but may as well give it a shot!

Thanks

Steve

 

Havent seen it done but i know an ls1 iac runs on L98 ecm's with little issue, but i think theres a different step count between the sensors, so the ls1 iac settings may need modded if possible. I didnt do anything on my L98 tho and never noticed idle control issues.

 

Never mind,found an issue tonight Lol. Rubber plug blew off the old pcv port under the runners.Happened at the track on the last run. Funny as it would run ok sometimes.
It still isn't 100% but not bad. Would still like to get it totally gone.It's better with the VSS unplugged.I'm also running that tail shaft adapter that has the mechanical drive for the speedo & the proper reluctor ring & sensor for the LS1 PCM so it's getting the correct PPM.
It's the last little bug to be worked out of the whole set up so will keep trying!

 

Try a LT1 TB. Bolts on the same as a TPI and uses the new sensors