Howdy everyone. Just got a quick question for y’all. My F150 is a 97 5.4 V8 and she’s been idling a bit odd when I first start the truck. I understand that a cold engine start will be different, but she just doesn’t have the same roar coming out the duel exhaust that she once had a few months ago. She turns over just fine every time, but it’s kinda like a lethargic start. For a few months I had a lean code, because the pcv valve was loose. That is fixed and there are no other current codes. I’ve been told everything from the injectors being bad to needing a new engine. I’m pretty good with engines, but sometimes I have no idea. Any ideas of what it could be, cause I’m stumped? Any helpful responses will be much appreciated. Take care and God Bless

 

I had a similar experience with my 1999. It eventually got worse and turned out to be the IAC. Never turned on the engine light or gave me a code.

 

Test the fuel pressure and tell us what the reading is.

 

I highly doubt you'd need all new injectors as not all of them would fail at the same time. I also think you'd have major engine codes if the engine was worn out.

I'd start by removing and cleaning the MAF sensor with MAF cleaner or QD electrical contact cleaner. Warning, don't turn ignition On until the MAF is perfectly dry. I'd also remove both throttle body and IAC valve and clean them with throttle body cleaner. I wouldn't worry about spark plugs as you say there's no misfire codes. Air cleaner should be relatively clean. Have you ever changed your fuel filter? How many miles ago? You've never noticed any kind of EGR codes implying a slightly open egr valve?

 

The cold start sequence needs to be understood in order to recognize an issue.
Cold start should be no more difficult than a hot re-start.
Both work exactly the same except for the temperature involved.
COLD starts:
Key on powers the computer, samples the Intake air temperature and cylinder head temperature. It's the only way the system knows the difference between cold and hot starts.
From this the computer sets the ignition timing advanced, richens the fuel injection , opens up the intake air control.
This results in a smooth cold start at some higher idle speed point that comes down as the engine temperature rises.
You can see from this operation that there can be fault points in the total sequence.
.
Test fuel pressure, clean the Iac and throttle body, be sure the there are no codes for the cooling system and use a Scanner to look at the live data for indications of out of normal readings.
This is why you sense a difference. The system still works but not the way it is designed to.
If your sure the hot starts and run is ok, that tells you the cold start issue is not fuel injectors.
It could be the CHT out of spec, Iat out of spec etc.
You have to look at all these areas to discover the cause or it's just guessing.
Good luck.

 

Since my '01's computer seems to loose it's mind from time to time, a computer reset would be the first thing, if it were mine.

 

 

 

Thank you for replying. I’m gonna find a good video of how to clean or just replace the IAC. I’m also gonna clean the throttle body and intake blade

 

News flash! Your ford does have a computer and it controls most everything, And it needs to be reset per the above vidio, as a starting point.
Good luck to you.

 

I think he's misunderstanding the use of "computer" to mean a diagnostics computer.

 

They mean the onboard engine computer, commonly referred to as the ECM or PCM, not a diagnostics computer.

 

Here is a write-up with images here on this site on how to clean the IAC.
https://www.ford-trucks.com/how-tos/...c-valve-430372