2000 sport 4.0 SOHC High Rev's at Start up

[tbirdman]

Hoping someone might have some insight into this minor- but annoying problem. Seems my 2000 Sport at start wants to rev up to 2000 RPM ( just sounds like foot on the accelerator). It goes down to fast idle af about 1500 RPM when cold - then after 1 minute down to about 800 and all is well. Now - even when hot - if I shut down the engine and start it up immediately again- revs freely up to 2000 RPM and then drops back down to 600 ( hot idle RPM- Normal) . Talked to shop foremen at dealership- offered some idaes but nothing conclusive without hooking it up to test equipment . ( i.e.- its going cost to find out the problem !!) I haven't seen a MIL light at all { other then the start up bulb check }- and other then the high rev start up problem- it runs great ( with only 20,000 mile- it should !! ) I am thinking TPS or IAC but curious if others have had this problem. Thanks for your info.

P.S.- Have already tried disconnecting battery overnight and "teaching " PCM my everyday driving style. The high rev at start problem ALWAYS comes back - go figure .

 

[BradE.]

If the IAC were bad, you would be having low idle trouble and probably stalling.

I'd check for vac leaks.

 

[Runnin'OnEmpty]

Tbird, my 2000 Sport does exactly the same thing. It's an OHV with about 42K on it. I also think that's an excessive start-up idle, and have been trying to figure out a way to lower mine.

I'm going to tinker around with it this Saturday. If anything works, I'll post it......

 

[tbirdman]

Hey Runnin onEmpty- thanks for the info- good to know that I'm not alone. Also did a recalls /TSB search at dealer- inquired about the manifold O-rings and cam shaft chain tensioners-. Its still a valid recall for 6 years or 70,000 miles, but again- this doesn't seem to be problem. The fact that yours doing it as well- maybe- just maybe- PCM programming glitch ?? My engine is late '99 production ( around Nov. 30- I think ) and the build date on the sport about Dec. 12-16, 1999. Not sure if that coincides with similar dates for your truck. I just came back from another disconnect battery for thirty minute and then drive for 30 miles stop & go city and freeway test drive. This to help PCM re-learn ( again) my driving style. Also did 4 stop & restarts- all good so far with hot engine. But - will have to wait & see when it comes back. Good luck to you and be interested to know what you find.

 

[Runnin'OnEmpty]

Tbird, my build date is Oct 04 1999, so our X's were indeed built close together. Hope your ECM re-set fix is permanment; keep us informed.

Here's my Saturday plan:
I intend to first clean the throttle body to get a good starting point. Then I will remove the IAC and tape up the air holes, and adjust the throttle stop screw to get a slow idle of 450 rpm. Then clean the IAC and reinstall, and check the TPS signal voltage. The IAC should then increase the idle to normal. A Ford tech suggested this procedure as a way to cure erratic idle conditions.

The IAC is supposed to have a duty cycle of about 32-36%. (I don't have a scanner, so I'm using the "old school" method.) I'm thinking the throttle plate is too far open at start-up, and giving the fast initial idle until the IAC compensates.

If this theory is correct, maybe a (new hire?) German tuner on the assembly line in Cologne, was setting the stop screw in to get a good clean engine start, but this opened the throttle plate too much for real world operation......???

 

[tbirdman]

Running On Empty- what your saying makes a lot of sense. This is why I was speculating TPS problems as well. If the TPS spends a lot of time at any one position ( like idle , for instance) in theory- the carbon tracking on the TPS potentiometer could become worn or go out of range. Now- that should register a MIL- but so far nothing. The only other thing then would be IAC. What you have described for a trial with removal, manual idle set & then re-install IAC sounds promising. If nothing else - it should eliminate the IAC as a problem. I was going to check and adjust TPS this weekend but I'm an old schooler too. I'm going to try for as close to 1.00 volt at rest ( key on- engine off) .Not sure if that would be correct- will compare to factory preset. The "as close to 1.00 volt setting" is a throw back to my '89 5.0 L Mustang LX- worked great there and best performance too. That littel jewel of information right out of the pages of Mustang monthly years ago- man - I'm getting old!! Try that IAC fix- and hats off to your Ford Tech- smart cookie that guy is .

 

[xplorerchic]

i JUST had my IAC replaced and it did stall out without giving it gas but i had unusually high RPM's in park and when i first started it up ...

 

[03ExplorerSPT]

The same thing happens on my 2003 Sport. Should I have it looked at?

 

[XLT Xtreme]

Hey guys I have the same problem in my 99 SOHC. Keep us updated as you find anything out.

 

[tbirdman]

Seems like us fortunate souls with the '99 & up 4.0 L SOHC equipped Explorer Sports have the same or very similarr problems with the high revs at start up. Sorry to here you having trouble still explorerchic- I will try and find some helpful info if I can. Maybe your IAC problem can be cured by the disconnect battery for 1/2 hour and then drive 30 miles or so. ( I 'm sorry if that sounds repetitive but you know what- I replaced a thermostat on my '85 F150 . It was the first year of fuel injection. It wouldn't run right with the new thermostat- erratic idle and stalled or revving at 1500 RPM- no happy medium. ( This was long before code readers or MIL lights too !! - about fall of '87) .Finally - cruising through pages of HOt Rod magazine where they were just finishing a TPI- 350 Z-28 into S-15 swap and the author wrote how he had similar idle problems. By chance he left battery disconnected overnight . Tried again in morning - and all was well. Idled smooth, good throttle response. I took a chance and it worked for me. Now , of course - clearing codes and disconnecting battery is common place- but hey - for you explorerchic- its worth a try- just some time thats all.
03explorersport- if yours still revving high at start- see if you can't get dealer to check out on warranty ( it won't cost anything - and maybe you find something out we can all make use of. ) We are talking about a brand new vehicle here- so your SOHC should have the latest & greatest parts and PCM programming. If you can get dealer to check- it would seem like it would be worth doing for some peace of mind.
Heres to hoping we can get some more useful info and feed back from explorer enthusiast like yourselves. Stay tuned.

 

[Runnin'OnEmpty]

Ummm.....this seems to be a common problem. I wonder if there's anyone with a 99 up that DOSEN'T have a fast idle at start-up. If so, it'd be interesting to know exactly what rpm it does start at.

Tbird, is your start-up idle OK now? Was the battery disconnect a permanent fix? I tried this several months ago when I bought the X, but I may not have left it disconnected long enough.

I am still going to try the throttle stop screw adjustment procedure. I'll post the results afterwards, good or bad.....

 

[Stig]

I have an 02' Sport... Mine starts fine at 1000rpm then after a long warm up to 600rpm.. Has 14K on the clock..

 

[Runnin'OnEmpty]

Thanks, Stig. That gives us a base for a 'normal' initial start.

 

[Majisto]

Mine idles somewhat quickly when it starts up, but that's usually because I start it when it's cold, and the engine speeds up the idle to warm up the cats. It's normal for a racy idle for about 10-20 seconds.

 

[tbirdman]

Hey running on empty- it starting to creep up - that cold start idle. For first day or2- about 1200- 1400 RPM- a normal cold start idle and back to about 800 after a mniute then 600 after 3 minutes ( again -all normal). But- started it today- and it edging up again- peaked at about 1600 then backed down again to normal. And you can tell- it just sound like the acclerator was punched the moment it fired up- then it catches itself and comes back to a more normal speed. However- I am trying one new start technique -that is keeping it at ( so far ) less then the 2000 rpm screamer. I turn key on and wait for all warning lights , bulb checks etc to cancel ( those that will cancel while waiting to start ) and then breifly engage starter till it fires. It works- but the proof will be when the hot start consistently does not rev up tp 2000 rpm before settling down. Until then- I am still looking for answers , too.

 

[DaleG]

You may want to replace your thermostat. One symptom of it going bad is high idle, because the computer is compensating for the low engine temp. there have been a few people here with that problem when it first starts to go bad but don't necessarily see any temp problems on the guage. If I remember correctly I believe there was a good thread on this posted by Robert, try searching to see if you can find it. It's probably about time for a new one on the 2000's. I just replaced mine on my 97 SOHC, it's not too bad but the back bolt is kinda of a pain but removing the throttle body makes it a little easier

Dale

here's the link to the post i was referring too, see if this is similiar to your problem http://www.explorerforum.com/forums/showthread.php?threadid=26381&highlight=thermostat

 

[aldive]

My 99 SOHC developed a fast idel problem and a thermostst replacement immediately solved it,

Take a look at http://www.explorerforum.com/forums/showthread.php?s=&threadid=83507&highlight=fast+idle

 

[Runnin'OnEmpty]

Dale and Al, thanks for the info on fast idles and thermostats. I'll remember that.

The fast idle that we're experiencing is at initial start-up. Mine flares up to about 1800 rpm, and then settles down to normal after a couple minutes.

This morning I unbolted the IAC and taped up the intake holes. The engine then started and idled at a very slow idle, just at a stall. This test is normal for the throttle stop screw setting, so I left it alone. After that, I cleaned the throttle body and IAC, and lubed the IAC plunger mechanism with WD-40. I rubbed some dielectric grease on the IAC O-ring seal, suspecting a vacuum leak. None of this caused any change whatsoever.

ExplorerChick, did your RPM's flare unusually at start-up? And a new IAC solved it? I'm beginning to think the IAC is at fault. Maybe the plunger spring gets weak over time........?

 

[2001ExpSport]

HI, I have a 2001 Sport and I was just posting to let you guys know mine runs fine. No rough idle and not one crazy high rpm start up. Oh and to just rub it in a little more, I have 67,000 miles on it.

 

[Magicfan25]

my 98 revs to almost 2000 right when you start it before it falls to idle..this is normal..i dont see how this considered a problem,,i dont know any car that doesnt rev a little right when you crank it up