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Idles high after starting

FJC

New Member
Joined
June 29, 2004
Messages
9
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City, State
Watertown Mass.
Year, Model & Trim Level
1997 XLT
Help please,
I have a 1997 5.0 AWD and just started to act up.When engine is first started,engine races to about 2500 rpm and after a minute or so returns to normal idle of around 900 rpm. Runs normal for the most part but sometimes engine will run at higher rpm (1200 rpm) when driving along and not touching gas pedal. Truck has 112,000 miles and was bought new and has not been touched by anyone but myself. Engine and electronics seem O.K. to me and engine light is not on or flashing so I would guess it does not have any codes in it. Other than plugs,wires,exhaust air tube(At 60,000 miles) I have not done anything to the engine(routine service only). Would like to get some help from someone that knows whats wrong or some things that may cause this problem. I have been a mechanic since high school but for the last 10 years have been working on motorcycles only and I am now out of touch with this stuff. I would go after the MAF or IAC but not sure if what I have going on would be a sympton of those or not. I would not want mess with them if its not the problem.
Also have never changed the fuel filter but would think a clogged filter would give me an opposite problem.Also needed is an oil change as this truck just got back from a 4000 mile journey and ran perfect the whole time,thankfully. This is my first post and just registered today as well.Thanks for any help and advice. FJC
 



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No, I have not done anything as I was not sure what to do.Do you think that is something I should do? I am afraid to make the problem worse by not properly doing something. Is there a procedure for cleaning IAC. Sorry for my ignorance but my experience with cars these days is limited. Thanks for your reply. FJC
 






Some carb cleaner would probably work fine. The IAC on my OHV is on the right side of the intake manifold. Just do a search on IAC and you'll find better info than I can give you. They're also fairly cheap if you need to replace it and you do it yourself. Your problem kinda sounds like a vacuum leak too, check your vacuum hose tree and make sure all the hoses are on tight. Good luck
 






Thanks for replies and please dont stop as it is not fixed yet,but I did check for vaccum leak as that was easiest and found nothing and did not hear any hissing under the hood. In the past when working for Chevy dealers there was a lot of IAC failures and since I am not up on these things I was unsure where to go.We use to just hose the spindle with carb cleaner and reinstall and 50-50 was the fix ratio.Same on the Fords? Tonight I am going to work on it and see what happens. Hope I dont make it worse! I was really looking for someone that had the exact problem.No such luck though huh? Again thanks so much.FJC
 






I say continue to chek for vaccum leaks, around the intake upper and lower manifold, also around the throttle body and brake booster...
You can clean the IAC and MAS then reset the battery, it might just fix it.
 






Another possible is the TPS.
 






Hmm, How is your power draw? I thinki maybe if you draw too much power the engine may idle up to give the alterntor more power. But I am no expert.
 






MAF, IAC, TPS, new air filter. And I've also noticed that my explorer always seems to idle/run better on an oil change...and I've stopped using FRAM because it seemed to make it run worse. Don't know what it was with those FRAM oil filters but it just didn't idle quite right with them. I'm sure it has something to do with them restricting the flow of oil to the engine. They will also cause a lack of oil on startup and you'll hear your engine starving for lubrication. Anyway, could be your throttle plate sticking open a tad causing high idle. Mine was so gunked up it would stick closed, but I suppose if the gunk were just right it could keep the throttle plate cracked open an "RCH" causing the high idle.
 






I was really looking for someone that had the exact problem.No such luck though huh?

Yeah I've had that problem twice. First time I took it to a shop, barely got it there cause it kept dying. They replaced the IAC. Second time I blew my cruise control hose off the vacuum tree and it would just rev up to 2k and then go straight dead unless I floored it, finally found the missing connection right before I called a tow truck.
 






Thanks for all the advice.Anyway,took out IAC and cleaned it with carb cleaner,checked hard for vaccum leaks and didnt find any.Still the same problem.One thing though,once idle comes down from 2500 rpm the engine runs perfect and takes about a minute to come down. Does not stall,sputter,cough. Stays at 900 rpm until the next time you shut off and start again then does the high idle thing again.No engine light coming on. What about the EGR valve? Would that cause that type of problem and not set a code because it is not connected to the computer? Seems odd that the light isnt coming on.Even high idle for 1-2 minutes should set a code but maybe because its happening before the computer goes into normal mode it isnt seeing it? I am going to clean MAF tomorrow but am thinking if it was computer related it shoud be tripping the light.Even a vaccum leak should cause improper mixture condition and trip the light?Screwy 02 readings or something. Never thought I would be saying "I miss carbs".Oh well I will keep digging for info and see if I can fix it without sending to some shop that may or may not be able figure it out. If I or someone else figures it out I will let everyone here know.I will keep checking all these posts until it is fixed.
One other thing is the doors stayed open all day while cleaning the rugs and problem seemed to begin after that but I charged battery after I was done.
FJC
 






Vacuum leak won't set a code (mine didn't and it was big), EGR will though if it's the problem. I dunno man, pull off the battery cable for a bit to reset the computer? Can't hurt
 






I was thinking a vaccum leak would make engine lean and set a code.This is so strange because it runs normal after it does its thing at startup.I would also think a vaccum leak would make engine run at a high rpm all the time?Everyone seems to point to vaccum problem but I cant find it or hear it.Would it be possible to leak vaccum for a minute and then not until the next startup?Is there a way to check intake manifold for leaks? This is the trucks first drivability problem it has ever had.I have not checked for codes in computer because I do not know how but light has not come on either.Could it have something set in there and not trip the light?Will disconnecting the battery clear them out if there was any in it? Thanks,FJC
 






You may need to actually replace the IAC. I have a startup idle problem stemming from the IAC on mine (also 5.0). It idles extremely low until it "pops" and then idles fine. When I clean the IAC, it idles OK on startup for a few days and then it's right back to where it was. I just ordered a new IAC on www.fordpartsnetwork.com so we'll see.
 






Light came on today.IAC code.Installed a new one for 90.00 and all better. A lot of good info from the people here. I am now better prepared for future problems as well, thanks to everyone!!!!! FJC
 






Glad to hear it. Not to burst your bubble, but you could've gotten a Motorcraft IAC on fordpartsnetwork for $61.00. But, I know how it is when something's not running right. You want it fixed IMMEDIATELY.
 






You are right about the fixing it fast.When faced with a broke car we pay whatever it cost right then and there to get it working fast.Still a shop could have charged many times the extra I paid and been without the car for days.Thirty bucks seems like not alot when you look at it that way.By the way that was supposed to be jobber cost from the dealer that supplied it to me! Ya right!!!!!!! Again thanks to everyone.Bunch of lifesavers here.I am sunk without wheels.I suppose I could take public transportation but have not been on a bus since I got a drivers license. FJC
 






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