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weird start-up idle

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Old Dec 14, 2010 | 09:01 PM
  #1  
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From: Milton,Ont,Can.
Thumbs up weird start-up idle

I am a new poster on this very informative site !! My wife can't understand how I could be reading and learning so much about my vehicle night after night .

I just bought a used 2002 Ford F250 7.3 powerstroke diesel . From what I can figure , it has an S&B air intake , 4 inch exhaust from the turbo back , 4 inch lift kit, and not sure about other mods done to it . Everything else looks stock to me but I'm still learning about it .

I'm hoping someone might be able to address this issue I'm having .

When I start my truck up in the morning , it starts good with no romps or anything , maybe a little blue smoke when cold . After idleing for about 3 minutes , the idle jumps up about 300rpms . I can get hit the throttle which brings it back down but also , if i hit the brake peddle , it also drops the idle down ??

I would like to know what you gentlemen might think would be causing this and maybe what to be looking for . Thank-you in advance for any advise .

This site is awesome !!
 
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Old Dec 14, 2010 | 09:05 PM
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Its a high idle feature. Normal. Meant to help it warm up faster as well as warm up the cab faster if your heat is on. Hitting the throttle or brake will bring it down to normal idle. There is also tale that bringing the idle up when idling for a long amount of time will help to keep fuel stacking from happening. (Deposits around the valves.)
Depending on what mods it does have, it could even sound like a jet engine spooling up. Some more than others.

Although if it is going up to 300 RPMs then you have a lower than normal idle. If you meant 3000, that is almost red-line and shouldn't go up more than to about 1100-1300 RPMs. If it really is 3000....something else has been added for a high idle and is set WAY wrong.
 
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Old Dec 14, 2010 | 09:06 PM
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Absolutely normal, it helps to warm up the engine faster, and keep it warm if you let it idle for too long when it's cold.

Damn, you beat me, BillyBob...

Oh, and welcome to the site... Warn your wife you need to use the checkbook a bit more now...
 
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Old Dec 14, 2010 | 09:10 PM
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Originally Posted by dadsgreenpsd
Absolutely normal, it helps to warm up the engine faster, and keep it warm if you let it idle for too long when it's cold.

Damn, you beat me, BillyBob...

Oh, and welcome to the site... Warn your wife you need to use the checkbook a bit more now...
 
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Old Dec 14, 2010 | 09:26 PM
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Thank-you gentlemen for your quick response .

Like I said , when she starts , it idles about 750 rpms then jumps up to just maybe 1000 to 1100 rpms .

It's good to know that it is normal . Thanks again . I'm sure glad to have found this site with all the great information .
 
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Old Dec 14, 2010 | 09:39 PM
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Originally Posted by BillyBob69
Its a high idle feature. Normal. Meant to help it warm up faster as well as warm up the cab faster if your heat is on. Hitting the throttle or brake will bring it down to normal idle. There is also tale that bringing the idle up when idling for a long amount of time will help to keep fuel stacking from happening. (Deposits around the valves.)
Depending on what mods it does have, it could even sound like a jet engine spooling up. Some more than others.

Although if it is going up to 300 RPMs then you have a lower than normal idle. If you meant 3000, that is almost red-line and shouldn't go up more than to about 1100-1300 RPMs. If it really is 3000....something else has been added for a high idle and is set WAY wrong.
Mine goes up 300RPM and it's all stock. It jumps from 800 to 1100. At warm idle it is maybe 700
 
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Old Dec 14, 2010 | 09:45 PM
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Just like posted above - normal condition. IIRC there are 4 parameters that have to be met in order for the idle to bump up.

1. OAT (less than 35 degrre IIRC)
2. Engine oil temp lower than normal operating temps
3. Vehicle in park
4. brake pedal not engaged.
 
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Old Dec 14, 2010 | 10:07 PM
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Ok. I'm a dork. I get what you were saying. Goes up an additional 300. Doh!
 
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Old Dec 14, 2010 | 10:42 PM
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Originally Posted by BillyBob69
Depending on what mods it does have, it could even sound like a jet engine spooling up. Some more than others.
This jet engine sound, does it sound like alot of air rushing by? I just replaced my EBP sensor and tube, and now my truck starts to make large air rushing noises when it is cold. (temps here have been mid to high 20's). Sometimes it does it when I am driving, right around 1500 RPM's, and then the power drops off a bit. Is it this high idle feature kicking in? Or something else?

sorry if this is a bit of a thread jack.
 
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Old Dec 14, 2010 | 10:52 PM
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Originally Posted by rocketman2440
This jet engine sound, does it sound like alot of air rushing by? I just replaced my EBP sensor and tube, and now my truck starts to make large air rushing noises when it is cold. (temps here have been mid to high 20's). Sometimes it does it when I am driving, right around 1500 RPM's, and then the power drops off a bit. Is it this high idle feature kicking in? Or something else?

sorry if this is a bit of a thread jack.
This is your exhaust back pressure valve (EBPV) closing to help warm the engine back up again. Yep, makes it sound like a giant leaf blower and when it happens while driving it kills the turbo and drops the power.
 
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Old Dec 14, 2010 | 11:00 PM
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Thanks for the reply! I can stop worrying now. Love this place!
 
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Old Dec 15, 2010 | 08:32 AM
  #12  
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I know the feeling - when that happened to me my first winter having the truck I thought:

"What the ..........
 
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Old Dec 15, 2010 | 09:26 AM
  #13  
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Stoked, someone posted this topic. Had it happened to me last week, down here in freezing So-Cal...., so hauled butt on the forum at 6am, and couldnt find anything, so i thought i had the "romps". Changed the oil, from Rotella 10/30 syn blend, to Rotella 15/40, and now, no issues.

Had thought it was the high idle feature, but my ebpv is gutted?
 
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Old Dec 15, 2010 | 10:09 AM
  #14  
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When the EBPV kicks in while driving, can it sound like air is being sucked in thru the cabin air ducts? The description fits my situation, but I swear it sounds like air is being sucked "backwards" from the cabin into the vents. Yeah, I'm crazy.
 
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Old Dec 16, 2010 | 03:35 PM
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Found this OASIS Broadcast Message-

0671 1994-2003 F-SUPER DUTIES, 1995-2003 ECONOLINE AND 2000-2003 EXCURSION 7.3L DIT ENGINE MAY EXHIBIT LOWER POWER WHEN COLD, AND AN AIR RUSHING NOISE
NORMAL OPERATION - EXHAUST AIR RUSH NOISE AND LOWER POWER. SOME 1994-2003 F-SUPER DUTIES, 1995-2003 ECONOLINE AND 2000-2003 EXCURSION WITH 7.3L ENGINE MAY EXHIBIT LOWER POWER WHEN COLD AND AN AIR RUSHING NOISE. THE TURBO CHARGER EXHAUST IS RESTRICTED BY THE EBP TO HELP INCREASE ENGINE COOLANT TEMPERATURE QUICKER FOR CAB HEAT. THIS IS CONTROLLED BY THE PCM & THE EBP REGULATOR LOCATED IN THE TURBOCHARGER PEDESTAL. THE EBP DEVICE WILL OPEN WHEN THE ACCELERATOR PEDAL IS DEPRESSED CAUSING EXHAUST BACK PRESSURE TO INCREASE. WHEN EXHAUST BACKPRESSURE DECREASES OR THE VEHICLE IS AT A STEADY STATE THE EBP REGULATOR CAN/WILL ACTIVATE THE EBP DEVICE AGAIN EVEN DURING HIGHWAY DRIVING AS LONG AS THE EOT TEMP IS BELOW SPECIFICATIONS. PCM CONTROLLED ON THE FOLLOWING PARAMETERS: IAT BELOW 10C(50F) & EOT BELOW 70C(158F)
 
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