High idle at cold startup?
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Fleet Mechanic
Joined: Nov 2004
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From: Michigan
High idle at cold startup?
My F150 in signature has a high idle when started up cold.
I always thought that was normal.
I have a 95 Bronco as a plow truck at work. It has a SD 351W and when I start it up cold, it settles right in to a low idle. Never has the high idle during warmup.
Q: What is normal? Does the MAF and SD have anything to do with it?
No codes stored on either one.
I always thought that was normal.
I have a 95 Bronco as a plow truck at work. It has a SD 351W and when I start it up cold, it settles right in to a low idle. Never has the high idle during warmup.
Q: What is normal? Does the MAF and SD have anything to do with it?
No codes stored on either one.
Elder User
Joined: Feb 2007
Posts: 601
Likes: 1
From: Chicagoland
Originally Posted by alz
My F150 in signature has a high idle when started up cold.
I always thought that was normal.
I have a 95 Bronco as a plow truck at work. It has a SD 351W and when I start it up cold, it settles right in to a low idle. Never has the high idle during warmup.
Q: What is normal? Does the MAF and SD have anything to do with it?
No codes stored on either one.
I always thought that was normal.
I have a 95 Bronco as a plow truck at work. It has a SD 351W and when I start it up cold, it settles right in to a low idle. Never has the high idle during warmup.
Q: What is normal? Does the MAF and SD have anything to do with it?
No codes stored on either one.
Calvin
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Joined: Feb 2007
Posts: 601
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From: Chicagoland
Originally Posted by alz
Yeah, I'm thinking the high idle is correct also.
The Bronco seems to idle smooth with no fluctuations. Does the IAC control the high idle? Or is this common to SD systems?
The Bronco seems to idle smooth with no fluctuations. Does the IAC control the high idle? Or is this common to SD systems?
What I know for sure is that the MAF 302 in the Bronco is acting perfectly normal. Someone else will need to chime in on the SD 351, but to me it doesn't sound right.
Calvin
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Fleet Mechanic
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From: Michigan
Yes, I think my F150 w/ MAF 302 is working properly with the high idle.
I'm not sure if the Bronco w/ SD 351 is working correctly. It has no high idle.
96onefifty and mprice, you both have MAF and mimic my own MAF truck. I think the Bronco is the one that has the problem. Just not sure if this is a SD thing or if, like mprice said, it may be a IAC problem.
I'm not sure if the Bronco w/ SD 351 is working correctly. It has no high idle.
96onefifty and mprice, you both have MAF and mimic my own MAF truck. I think the Bronco is the one that has the problem. Just not sure if this is a SD thing or if, like mprice said, it may be a IAC problem.
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From: Bonita Springs FL
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Fleet Mechanic
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From: Michigan
If it were the ECT, would it have problems starting? It starts right up, no hesitation.
Probably the IAC. I'll give it a good flushing when I get a chance at work.
Throttle body cleaner or brake/parts cleaner ok?
Probably the IAC. I'll give it a good flushing when I get a chance at work.
Throttle body cleaner or brake/parts cleaner ok?
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From: Nebraska
I don't think anything is wrong with your truck. The PCM is calibrated different depending on year, engine, and transmission.
My 95 and my retired 95 with a MAF 302/4R70W both start with a high idle (the 5 speed truck is SD and slightly higher). In the summer the MAF truck starts 'cold' with a lower idle though. Both go down to normal in about a minute.
I'm running a 95 SD 351W/E4OD computer in my 79 F-150 right now and it starts cold with a nice lower idle like alz described. I've noticed this on other newer 351's also. Just different programming.
My 95 and my retired 95 with a MAF 302/4R70W both start with a high idle (the 5 speed truck is SD and slightly higher). In the summer the MAF truck starts 'cold' with a lower idle though. Both go down to normal in about a minute.
I'm running a 95 SD 351W/E4OD computer in my 79 F-150 right now and it starts cold with a nice lower idle like alz described. I've noticed this on other newer 351's also. Just different programming.
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Fleet Mechanic
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From: Michigan
Good to hear.
When the Bronco was idling today, I pulled the plug on the IAC and it nearly stalled. That's good to know it is working.
I guess it's just the characteristic of this vehicle.
I guess, no harm, no foul. It runs and drives fine.
When the Bronco was idling today, I pulled the plug on the IAC and it nearly stalled. That's good to know it is working.
I guess it's just the characteristic of this vehicle.
I guess, no harm, no foul. It runs and drives fine.
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i have 87 and 92 f150 302 and a 95 f350 351 the 302 act alittle diffrent cold than the 351 seems like it has to get colder for the 351 to idle as long or really up.Because i drive the 350 for work i drive it every morning. if i get in my 302 i m impatient to get going lol takes about 1 min or so to slow down.Unless it is wanting to start hard or stall i would just let it warm up a few min and go.Of course i could have the same problem you do and don t know it . but both start and drive good 19.8 hi 302 empty 10.8 hi 351 loaded to the hilt
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I have SD so lets kill that theory now 
It should'nt stall if you pull the plug on the IAC either... in fact the IAC shouldnt do jack if you pull the plug on it, im guessing the computer sensed a problem and went into limp-mode or something
it was probably put back together wrong, or just failed and doesnt even move anymore
It should'nt stall if you pull the plug on the IAC either... in fact the IAC shouldnt do jack if you pull the plug on it, im guessing the computer sensed a problem and went into limp-mode or something
it was probably put back together wrong, or just failed and doesnt even move anymore
Last edited by dr1; Dec 2, 2007 at 11:21 AM.
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Fleet Mechanic
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From: Michigan
So you are saying that the IAC doesn't do anything for the idle?? Isn't its purpose to control the idle? If you remove the plug to it, would it not close off the air going into the throttle body? The engine did not stall, it almost stalled.
As far as being put back together wrong, it's never been apart.
As far as being put back together wrong, it's never been apart.
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its a stepper motor, when you removed its power it shouldve just stayed right where it was.. which it probably did, stuck from being broken or gummed up with crap
yes, thats what it is there for.. other then a lack of response in rpm, etc.. the computer doesnt actually know if the device is working or not, other then just being present... meaning if you were to scan the computer and get the IAC reading, it would tell you what position the computer is telling the IAC to be in, but not actually where it is
the entire air passageway itself could just be clogged
edit: im not ruling out the possibility your PROM could be adjusted that way from the factory, its possible, I just cant imagine why one particular oddball combo would be that way and not another from the same year.. and iac's go bad/get clogged regularly
yes, thats what it is there for.. other then a lack of response in rpm, etc.. the computer doesnt actually know if the device is working or not, other then just being present... meaning if you were to scan the computer and get the IAC reading, it would tell you what position the computer is telling the IAC to be in, but not actually where it is
the entire air passageway itself could just be clogged
edit: im not ruling out the possibility your PROM could be adjusted that way from the factory, its possible, I just cant imagine why one particular oddball combo would be that way and not another from the same year.. and iac's go bad/get clogged regularly
Last edited by dr1; Dec 2, 2007 at 04:38 PM.
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