After full top end tune up my $6e 88 TPI auto is idling and running good. Sits at 650 in drive, doesn't stall or surge in drive/park switches. I am getting the closed loop fuel dialed in. the closed loop I have not touched.


I notice though my start up hi-idle is like 1400 rpm. it stays there too long it seems and only drops to 900rpm and will stay there after fully warm for 30minutes of driving it might settle in to 875 range all in park.

if I go to drive it drops in gear and sits and idles normal.

I have notice all the RPM drops are related to the IAC. I replaced and cleaned IAC/TB and it responds and works well. Cold it goes to 140, then drops into the 90 range so 1400 rpm to 1000 rpm. after warmed up in park it seems to sit at the 30 range gradually it goes down into the 20 range and idles better around 850 but this takes way too long like half hour.

now after 5 minute warm from cold start and o2 heated in drive the IAC sits at 5-7 range and when I step on gas goes into the 40-60. all seems normal and works fine.


any code I change to force the cold idle IAC to lower values? Do I try to adjust the IAC again teach-in? or just lower the cold idle set point on the TB?

it just all seems to work really well mechanically so thinking it is ecu

 

I'd check for a vacuum leak before doing anything else. Could be that once it warms up the leak becomes smaller as things expand and thus RPM drops, but maybe not as far or as fast as it should. Also, if EGR is still operational, might check valve for sticking. Some $6e bins that have a 200 RPM bump when going to P/N from Drive (check 0x52B=Idle Speed adder in P/N). Too much IMO as 100 generally is enough. Some bins have 0. That might account for the 875-900 P/N idle from 650 in gear. Don't know why you're not seeing higher RPM in gear if a vacuum leak, but you might be because the stock $6e RPM at warmed up temp is generally 550 (check table at 0x52e=Idle RPM vs. Coolant Temperature).

 

As stated rule out the vac leak. Probable vac leak. Maybe in a vac hose. Does your def file show a IAC decay filter? I will guess a larger # will decay the steps faster. There is a coolant based IAC position but decay I dont believe is relavent there.