92 5.0 Won't Idle Or Hold Revs

[Josh02GT]

Car ran fine two weeks ago, now won't idle, wants to die when in gear and won't hold revs while in neutral with throttle partly engaged. Example - idling roughly around 500, give it gas to keep it alive and I hold it at 2K. The idle will just fall flat down 500-1500 revs fast like i turned it off, all while keeping my foot in the throttle, then it will finally wake up and pop up to 2K. It will do this over and over. This car is new to me, I don't have all the mod history. Here's what I've done so far - replace plugs, Clean TB and IAC, found and removed an ADS Super Chip from 1997, performed base idle reset procedure, check TPS voltage (got .97v). It idled fine once right after removing the chip, then back to crap at next start. Any ideas?

Mods - Edelbrock Performer heads and intake, unknown spec Comp cam, BBK 70mm EGR, stock TB (no idea why that's still stock), FMS big bore 70mm MAF for 30's, 30# injectors (I know, too big, car had a blower that died and was removed), Lentech AOD, off road X, Bassani catback.

 

[jrichker]

See the "Surging Idle Checklist” for help with all your idle/stall problems. You can guess at the problem and throw parts at it, or you can use the checklist to help you find the problem quickly and inexpensively. The checklist is right here in the Stangnet 5.0 Tech forum and you don’t have navigate to some other unknown web site. It‘s free and doesn’t cost anything: at last count there were more than 103,000 visits and still climbing

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.