2000 sport 4.0 SOHC High Rev's at Start up

[2001ExpSport]

Originally posted by 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

I'll second that.

Maybe you guys are using the wrong Antifreeze?

 

[xplorerchic]

Originally posted by 2001ExpSport
I'll second that.

Maybe you guys are using the wrong Antifreeze?

first of all, i think that we all understand that when you start the truck the RPM's go up .... the problem that we are having is that the idle isn't consistant .. i let my truck sit in park for 10 minutes and the whole time the RPM's jumped from 500-1200 hunting for idle ... my problem was because of the IAC ... its a 01 and has 38000 miles on it .... the people at ford said that it was possibly caused from carbon buildup ...

 

[Magicfan25]

ah ok.. the only time mine ever hunted for idle wsa 600-2000 and it was the intake gaskets. the colder it was, the worse it got

 

[tbirdman]

Running on empty- sorry to hear you had no luck with what you tried on your sport today. Me- I haven't been driving mine since thursday as I had to be out of town ( working on the farm- we are in the middle of harvesting right now). Now- you still are thinking IAC problems ? I am still wondering if possibly it could be a PCM programming issue as well ? I haven't got to read the TPS voltage yet- it might tells us something- not sure. One thing I do know- the 2000 RPM rev up at start is in NO way normal as some have replied to here. I have owned enough Fords ( 3 of them with SOHC motors of some variety) to know that fast idle on FORD fuelies at cold start does not exceed 1800 rpm under NORMAL conditions ( this includes the - 40 deg F we get in the winter up here and the 110 deg F in the summer ). Moreover - hot starts should never peak past 1000-1200 rpm at start and should fall immediately to 600rpm hot idle- again for normal conditions. I t seems there are more here that ARE having problems then are not- myself included - so I'm wondering if there isn't a TSB out ( or in the works ) that would address this problem. We 'll have to keep digging for answers. Anyone with some constructive information - we would sure appreciate it. Again - the problem being a high RPM ( 1800-2000 RPM ) peak at initial start- sounds like the accelerator has been tapped as the engine fires . Also- at hot start a high rpm peak of 1200- 1400 rpm at intial start ( again -like the acclerator has been tapped as engine fires ) . Idle characteristics, power , accleration engine temp, etc. are other wise normal. Thanks for keeping up with the investigation Running on empty - and heres hoping we can find some answers.

 

[Runnin'OnEmpty]

Update!

tbirdman, I sprung for a new IAC; no change in the problem.

According to my research, the PCM starts the engine with the IAC in the wide open position. (Why, I don't know; probably for emissions reasons) Then the PCM reduces the idle according to the various sensor inputs.

This got me thinking that restricting the airflow available to the IAC valve (only when it's wide open), would lower the starting rpm. So I cut a small piece of 3/8" neoprene fuel line and inserted it in the IAC feed tube. After re-installing the IAC, the start-up rpms dropped to 1300. This is a 500 rpm drop from what it was before.

Since I just did this today, and haven't driven it much, I don't recommend anyone else trying it. I also wouldn't try to lower the rpm any more than about 1200-1300 rpm. More restriction might overwork the IAC motor and get it out of it's duty cycle range.

 

[Nicaraguense]

It is supposed to start up on high RPM

It is supposed to start up on high RPM. That is just one more reason that you DON'T have to pump and pump the gas or not even pump the gas once on start up (like a carburated vehicle or at least ANY carburated vehicle I have ever owned) Also, you don't have to crank and crank and try and try again to start it (also like ANY and EVERY carburated vehicle I have ever owned. I EXPECT mine to hit high RPM at start up. If not, I think something is wrong (especially since I use Synthetic GOD I wish the IDIODS that abused it before me (used Pingzoil streight up crude oil) had used Amsoil) anyhoo, I just like think mine is fine (other than IAC) it gets too low when it comes back down. High on start up is correct.

 

[tbirdman]

Running On Empty- thats some good work finding that out about the IAC going full open at start sequence. I will be curious how your's works with your modifiaction for long term- if that's a good fix it sounds simple enough to do. And it might well be worth sharing with others if it works well. Good work, man. I haven't got around to checking for codes or other glitches either -but I like this info you have passed on here. Thank you.

 

[Runnin'OnEmpty]

Update Number 2

This is for Tbirdman and anyone else who is interested. The restrictor in the IAC feed hole will work to lower the high rev start-up, but that's not the way to do it. Here's the correct way:

At the plug end of the IAC, there's a 3/8" metal cap. Under this cap is an adjustment screw. To remove the cap, you need to drill a small hole in it, and take a pick and pry it out. The screw that is behind the cap adjusts the wide open range of the IAC. Turning the screw clockwise will narrow the gap opening in the valve, and reduce the start-up revs.

Ford keeps this IAC adjustment a secret, because I've yet to find anything written about it or a Ford tech that knows about it. (In other words, they don't want you messin' with it.)

Before touching the adjustment screw, make sure the low end of the idle range is correct; i.e. the engine dies after two seconds with the IAC unplugged, and the throttle body and IAC are clean. Also be aware that slowing the revs down too much might cause the engine to die at startup, and require another try, especially in the winter. (That is probably why Ford specifies the high startup revs in the first place).

Hope this helps.

 

[addkev]

Mine definately revs high at start up (1800-2000) and it almost sounds like it has a loose belt because it will let out a loud squeak for just a split second. But after that it settles down real low like 600-700 rpms.
In fact, I think it is too low, because the air compressor will start making weird noises at idle, and I have to rev it just a bit to get it to go away.
Mine was a Oct 98 build and it has 78k miles.

 

[RAZOR]

I have the same problem with a sudden fast idle. Sometimes, it happens after the engine is warmed up and sometimes when cold. My engine was replaced 3,000mi. ago. This was never a problem with the original. When I bring to Ford it never seems to happen. Drove to the dealer one time while it was happening,but it stopped by the time I got there. Notice it most times in bumper to bumper traffic. If anyone who is experiecing the same problem ever finds the cure post it. Thanks, Razor

 

[Runnin'OnEmpty]

Correction

Guys, I have to amend my previous post. After switching out my IAC tonight, I found that turning in the adjustment screw will only lower the startup revs slightly. It has a bigger effect on the fast idle than the startup rpm, so if your fast idle is OK don't mess with it.

I suspect turning the screw is changing the duty cycle of the IAC. It's supposed to be 24-28% for a warm idle, so I'm going to have to get a scanner before I can tell anything more about it. I'd take my spare IAC apart, but I don't want to destroy one that works.

Addkev, your low idle is probably caused by a dirty IAC; you might try cleaning it.

Razor, your erratic fast idle might be from a vacuum leak somewhere that comes and goes......?

 

[Grant RI]

Just found the thread after posting another just like it

Same problem on my 2000 4.O

Maybe its "normal" but it sure doesnt seem "right" to spin a cold,dry engine that fast.Mine goes ABOVE the 2000 rpm mentioned at start up and settles to normal idle immediately.

any more info on a fix? I'd at least like to develop a bit of oil pressure before gunning the thing to 2500 rpms

 

[Runnin'OnEmpty]

I'd at least like to develop a bit of oil pressure before gunning the thing to 2500 rpms

I feel the same way, Grant.

The piece of restrictor hose that I mentioned previously, dropped the start-up idle to about 1400 rpm, so I haven't done anything else to mine. It didn't trip the MIL nor does it show any trouble codes so far. I don't recommend this however; it's not the correct way to solve the problem.

You might try lubing the IAC shaft with WD-40. (The shaft might be sticking momentarily upon start-up, and keeping the valve from shutting quickly.) I would also try disconnecting the negative battery cable for 15 miinutes, to reset the PCM. Hope something works for you.

Don

 

[tbirdman]

Hi rev's at start up still a reality for me too.

Gentlemen,
I am sorry to say I am no closer to finding a cure to this problem then in the fall. Had the Sport to the dealer a few times- no luck there as I was told it checked out all ok - no MILs, codes , etc. Sometimes can go quite a while between high start revs - it actually starts good. Then it will come back with a vengeance - hot or cold. So- at this time- I am looking into a custom handheld programmer or performance chip mod as a way of tricking the PCM into forgetting the "wild" factory start sequence- but I really don't know if it will help and certainly wouldn't recommend trying this as it could be just "wishfull thinking". If anyone can come up with some answers - thanks for posting your info.