As the title says idle goes up and down on start up, and after a minute or so it'll straighten out.

1988 4.9l

New IAC TPS EGR

 

I would test vacuum and fuel pressure as well as MAP, ECT sensor and HO2S. And it never hurts to double check the IAC. if you haven't done so check for codes first.

 

Mine did that when running but after it was warmed up ran a couple bottled of berrymans b12 chemtool through and sprayed the throttle bodies using berrymans throttle body cleaner with it running and then not running and it blew some smoke out the pipe and had run great since I'm a firm believer in the stuff now. Warlock would know better than me but maybe that would help your problem

 

Vacuum sitting at 22 inches, don't remember fuel psi. But its good.

New map ect and o2

And no codes that would effect this

 

You pmc needs to relearn the idle with iac. This may take some time. If it don`t there is a pacer people put in and some fab a restricted plate for the iac. Google it.

 

Did this settle down?

 

It'll still do it every once ina while but definitely better

 

Put a little grease on it, it will help out.

 

On the iac?

 

Between the two holes on the iac there is a thing there that looks like a ball. Put some grease on both sides of it. Not much..