High Idle at Start Up?

BentSpurs

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When I start the engine after the truck has sat for a day or two, it will immediately idle up to 1,200 rpm. If I tap the accelerator pedal before it warms up the rpms drop down to around 750-800 which is where it idles after driven a while and parked.
Is this normal?
Concern is running high rpms before engine is sufficiently warmed up.
Thanks!

1996 E.B. 5.8, E4OD, 153k miles, original engine and transmission, Mobil 1 5W-30.
 

L\Bronco

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High idle on cold start is normal, they run them a bit faster to warm them up quicker and to try to keep the emissions down during warmup. As long as there is no load 1500-2000 RPM won't hurt a cold engine.
The PCM controls it and it should drop down on it's own as it warms up. If you have to tap the throttle to get it to drop you may have a sticking Idle Air Control valve (IAC). Pretty common as they age, they get gummed up with residue from the PCV vent. See if it drops on its own before trying to fix anything.
Hope that helps
Cheers
 
OP
OP
BentSpurs

BentSpurs

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High idle on cold start is normal, they run them a bit faster to warm them up quicker and to try to keep the emissions down during warmup. As long as there is no load 1500-2000 RPM won't hurt a cold engine.
The PCM controls it and it should drop down on it's own as it warms up. If you have to tap the throttle to get it to drop you may have a sticking Idle Air Control valve (IAC). Pretty common as they age, they get gummed up with residue from the PCV vent. See if it drops on its own before trying to fix anything.
Hope that helps
Cheers
High idle on cold start is normal, they run them a bit faster to warm them up quicker and to try to keep the emissions down during warmup. As long as there is no load 1500-2000 RPM won't hurt a cold engine.
The PCM controls it and it should drop down on it's own as it warms up. If you have to tap the throttle to get it to drop you may have a sticking Idle Air Control valve (IAC). Pretty common as they age, they get gummed up with residue from the PCV vent. See if it drops on its own before trying to fix anything.
Hope that helps
Cheers
Thanks very much. I’ll check that.
 

captsb890

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Thanks very much. I’ll check that.
I checked rail pressure--first key--20 or so pounds---then 2nd key jumps to 40---this is after it sits a couple days------but---with foot off pedal---it starts and hangs at 500 rpm--plopping---and then like it clears out jumps up to 1200 for a minute and right down to 700 idle------so what doesn't it jump up to 1200 right away after the second keying instead of hanging up about 20 seconds----------changed the MAP, TPS, different ICM----------do you think it might be the PIP or is it the EEC-IV computer ??---------after starting runs good all day---------------By the way, The engine has 204,000 miles and had timing chain stretch ----it had poor acceleration etc-a mechanic adjusted the timing to account for the stretch----Runs way smoother, shift good and smooth, little more pep--------------Do you think that might be what is causing the start hang up?? If so, it's a trade off----
 

Motech

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I checked rail pressure--first key--20 or so pounds---then 2nd key jumps to 40---this is after it sits a couple days------but---with foot off pedal---it starts and hangs at 500 rpm--plopping---and then like it clears out jumps up to 1200 for a miy after the nute and right down to 700 idle------so what doesn't it jump up to 1200 right awasecond keying instead of hanging up about 20 seconds----------changed the MAP, TPS, different ICM----------do you think it might be the PIP or is it the EEC-IV computer ??---------after starting runs good all day---------------By the way, The engine has 204,000 miles and had timing chain stretch ----it had poor acceleration etc-a mechanic adjusted the timing to account for the stretch----Runs way smoother, shift good and smooth, little more pep--------------Do you think that might be what is causing the start hang up?? If so, it's a trade off----
I think you're thinking way to much on this. Like @L\Bronco said, it's normal. Even the abrupt drop when you throttle might be normal and temporary too if you recently disconnected your battery.

You've heard that old saying, especially true on a 200K mile Ford small block:
  1. "Don't sweat the petty stuff bro; pet the sweaty stuff!"
 

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