'90 Idle Rpm Spec?

droptail · February 13, 2009

In trying to improve my mileage from 13 mpg avg, I've put back my OE TB. I need to know what the idle spec is (5.7L manual) for the setup.

Where in the OE service manual is this, I haven't been able to find it.

Thanks

superjim · February 13, 2009

idle RPM should be around 700 to 750.

kuhl_530 · February 14, 2009

700-800 sounds about right, but remember that's going to be idle with a warm engine. Cold mine idles between 900 and 1000 rpm (until i drive a mile or so, just to bring the fluids up in temp a little).

droptail · February 14, 2009

I've seen 600 +/- 100, thats why I ask. Also, I am a manual thats different from the auto's.

Heavy Cruiser · February 16, 2009

Manual/automatic, doesn't matter, ECM controlled idle rpm is the same.

What you should do is check/set base idle, 500-550 rpm.

Place ECM into diagnostic mode to extend IAC into its seat and unplug it.

Remove ALDL Pin A-B short and start engine already at operating temp.

Check and adjust idle as needed.

Stop engine, plug in IAC, remove diag code, check TPS setting and adjust if needed, otherwise code will show up.

Turn ign to on, no start, let IAC set for idle, then turn off key.

Restart engine, and idle should correct itself if in gear, A/C selected, and accessories are on. Idle should remain the same.

droptail · February 17, 2009

Manual/automatic, doesn't matter, ECM controlled idle rpm is the same.

What you should do is check/set base idle, 500-550 rpm.

Place ECM into diagnostic mode to extend IAC into its seat and unplug it.

Remove ALDL Pin A-B short and start engine already at operating temp.

Check and adjust idle as needed.

Stop engine, plug in IAC, remove diag code, check TPS setting and adjust if needed, otherwise code will show up.

Turn ign to on, no start, let IAC set for idle, then turn off key.

Restart engine, and idle should correct itself if in gear, A/C selected, and accessories are on. Idle should remain the same.

I followed instructions I had for most of this, but engine wasn't hot. I'll redo it hot.

Is there a method to erase codes without unplugging battery?

Thanks for the info.

James