Notices
1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

IAC or ? 1990 f150 4.9 efi

 
  #1  
Old 05-19-2019, 06:17 AM
Odisvan
Odisvan is offline
Elder User
Thread Starter
Join Date: Jul 2015
Posts: 547
Odisvan is starting off with a positive reputation.
IAC or ? 1990 f150 4.9 efi

Iíve sorted thru lack of fuel pressure and changed regulator and in tank pump was within psi and truck runs great.....once I get her going. Iím having to pump accelerator to get a fuel injected vehicle to start. Once it does, Iíll have to peddle a tad to get smoother idle and then itís great. Can reach thru window and turn key and immediate start, until it sits few hours and then same deal. Let it prime, try it, let it prime, pump, pump, pump, and itís the same old 30 second ritual and it might idle rough then and pump a time or two to rev and clears right up and itís no issue until parked and cools down good again.
as I have not removed my IAC or tried to clean it yet, Iím only presuming that would help, I thought Iíd offer myself up for suggestions. With a new fuel pressure regulator and in tank pump both at correct psi, verified by gauge kit, any other suggestions other than IAC cleaning or replacement? Cranking off and on and pumping accelerator pedal isnít even required this much on old carb. Yes have new ign tumbler and elec switch. As well as plugs and wires and coil and starter and battery cables and grounds cleaned.checked PCM removed and looked inside, itís like new, no leaky capacitors or anything out of sorts. Truck runs super save for this manual manipulation of throttle pedal to get her going. I thank you for your thoughts in advance, Odis Van.
if I unplug the IAC before cranking, would that demonstrate any measurable test?
 
  #2  
Old 05-19-2019, 06:25 AM
Odisvan
Odisvan is offline
Elder User
Thread Starter
Join Date: Jul 2015
Posts: 547
Odisvan is starting off with a positive reputation.
Forgot to mention truck sat for many years until I bought the abandoned non running hulk for cheap. At least 3-4 years of not running. And I have not ran any miracle snake oil in gas.
 
  #3  
Old 05-19-2019, 08:58 PM
midwestbird
midwestbird is offline
Junior User
Join Date: Mar 2019
Posts: 61
midwestbird is starting off with a positive reputation.
Originally Posted by Odisvan View Post
if I unplug the IAC before cranking, would that demonstrate any measurable test?
I do think I recall reading that a way to test the IAC is to unplug it and see if your engine behaves any differently. I also recall that I unplugged my IAC when I was chasing a hard start condition, and my situation got worse. Had my symptoms not changed any, I believe that would have been an indicator that my IAC wasn't functioning
 
  #4  
Old 05-20-2019, 07:01 AM
My4Fordtrucks's Avatar
My4Fordtrucks
My4Fordtrucks is offline
Posting Guru
Join Date: Jun 2015
Posts: 2,171
My4Fordtrucks is gaining momentum as a positive member of FTE.My4Fordtrucks is gaining momentum as a positive member of FTE.
What, if any, fault codes do you get and were they stored or active faults?
 
  #5  
Old 05-20-2019, 07:53 AM
jas88's Avatar
jas88
jas88 is offline
Post Fiend
Join Date: Feb 2002
Location: Greater Austin, Texas
Posts: 5,041
jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.
Pumping the throttle on a fuel injected engine does nothing except exercise the throttle blades. It has no effect on gas entering the engine. If you can open the throttle a bit and hold it and that makes it start, then your IAC is most likely at fault as you are letting in air that the IAC is not. You should clean it first and be sure to disconnect the negative battery cable while you do it so the ECU can re-learn the idle. Use a TB safe cleaner and an old toothbrush. Do not give in to the temptation to replace it with an aftermarket unit - they are mostly junk in my experience.
 
  #6  
Old 05-20-2019, 08:20 AM
Odisvan
Odisvan is offline
Elder User
Thread Starter
Join Date: Jul 2015
Posts: 547
Odisvan is starting off with a positive reputation.
I am going to take it off and clean it and report back. Once it does crank, it'll idle pretty high and I'll have to throttle it like an old carb to kick choke off, then it'll search for awhile and smooth out. And, then it'll be fine till engine cools off, then same thing. It'll always start and run, but once engine is cold, it's same procedure. Made my first blast thru subdivision yesterday, this is my $300 abandoned truck I put another $3-400 in so far, all trans gears great, everything good actually, except that starting issue. I felt I got a great deal on what might be a super reliable drivetrain for a 53 F1 I have spotted, that is intact with no drivetrain! Or, I might leave it intact. I don't see how I can lose either way, I feel the efi 300, overdrive auto, rear end alone are worth what I have invested so far.
 
  #7  
Old 05-20-2019, 09:09 AM
Scott Bowmaster
Scott Bowmaster is offline
Senior User
Join Date: Dec 2017
Posts: 107
Scott Bowmaster is starting off with a positive reputation.
Originally Posted by Odisvan View Post
Forgot to mention truck sat for many years until I bought the abandoned non running hulk for cheap. At least 3-4 years of not running. And I have not ran any miracle snake oil in gas.
Maybe a new fuel filter, and some sea foam or something similar run through the gas to help clean up the injectors a bit is all she needs?
And 100% on cleaning the IAC. But I think the old fuel might be more the issue
 
  #8  
Old 05-20-2019, 06:37 PM
95fiveoh's Avatar
95fiveoh
95fiveoh is online now
Elder User
Join Date: Nov 2016
Location: Pittsburgh
Posts: 646
95fiveoh is gaining momentum as a positive member of FTE.
My IAC was bad, cleaning it didn't make a difference. Here is how it behaved with a bad IAC-


And here it is with the IAC replaced-

 
  #9  
Old 05-20-2019, 08:00 PM
torq'ta 5 8's Avatar
torq'ta 5 8
torq'ta 5 8 is offline
Senior User
Join Date: Jan 2019
Location: N.W. Alabama
Posts: 267
torq'ta 5 8 is starting off with a positive reputation.
after its warmed up and idles on its own, unplug IAC and if IAC is bad or dirty it usually dies in 8-10 seconds, after unplugged
How to Clean and Test your IAC - Ford Bronco Forum
 
  #10  
Old 05-21-2019, 07:02 AM
jas88's Avatar
jas88
jas88 is offline
Post Fiend
Join Date: Feb 2002
Location: Greater Austin, Texas
Posts: 5,041
jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.jas88 has a great reputation on FTE.
My 300 used to idle up to about 1500RPM when I first started it, then it would settle down in about 5 secs and be fine until the next time I started it. Many other 300 owners on this forum reported the same, so we just decided that's the way Ford programmed it. I fixed that problem by replacing it with a 460.
 
  #11  
Old 05-21-2019, 04:44 PM
torq'ta 5 8's Avatar
torq'ta 5 8
torq'ta 5 8 is offline
Senior User
Join Date: Jan 2019
Location: N.W. Alabama
Posts: 267
torq'ta 5 8 is starting off with a positive reputation.
I bet that woke it up! Here let me pull your house down!
 
  #12  
Old 05-21-2019, 07:03 PM
Odisvan
Odisvan is offline
Elder User
Thread Starter
Join Date: Jul 2015
Posts: 547
Odisvan is starting off with a positive reputation.
Yep. I have rode in 460 trucks and owned 429. Great engine.
 
  #13  
Old 05-21-2019, 07:43 PM
torq'ta 5 8's Avatar
torq'ta 5 8
torq'ta 5 8 is offline
Senior User
Join Date: Jan 2019
Location: N.W. Alabama
Posts: 267
torq'ta 5 8 is starting off with a positive reputation.
my first new truck was 87 4.9 5spd,(never an issue) sold it and 77 power wagon, to buy first house in 93, pop had 65 F100 3 on the tree, straight 6, and the oil bath air filter, buddy had 66 F100 3 on the tree, 352(with 429 heads) it was a handful
 
  #14  
Old 05-21-2019, 08:56 PM
Odisvan
Odisvan is offline
Elder User
Thread Starter
Join Date: Jul 2015
Posts: 547
Odisvan is starting off with a positive reputation.
Removed IAC, separated stepper motor, and soaked fairly clean looking Pintle part in non ethanol gas overnight. Nothing in the clean gas, when working Pintle by finger, I could see black carb junk around it. I would have figured gas would have loosened that but no, but plunger seems to move freely with finger pressure.
forgot about disconnecting battery, but reinstalled. About same as before, several start attempts, when it does, it’s chugging and idles real high and doesn’t reduce until I kick throttle like a carb with choke. I unplugged IAC and it immediately dies.
 
  #15  
Old 05-21-2019, 09:06 PM
torq'ta 5 8's Avatar
torq'ta 5 8
torq'ta 5 8 is offline
Senior User
Join Date: Jan 2019
Location: N.W. Alabama
Posts: 267
torq'ta 5 8 is starting off with a positive reputation.
its bad dirty, see post #9 how to clean, they warn not to use brake cleaner, use throttlebody cleaner it will get the gunk out
 

Thread Tools
Search this Thread

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.