Very High Idle

Howdy guys, I have a 1990 Ranger with the 2.9. I just bought it from a friend that said it was leaking water into the combustion chamber. Well, he was right, so we took the heads off to have them pressure tested (the 2.9 heads are famous for cracking as you probably know). While getting to the heads, the lower intake bolts were not even finger tight, so we knew water was atleast getting in from there. Turns out, the heads weren't cracked and the head gaskets were in perfect shape. Had the heads resurfaced while they were at the shop. Must have been leaking between the lower intake and the heads, they were literally all loose, and the gasket was a bit crappy between the water passages and the air passages, presumably from water and antifreeze shooting through there for a while of course.

Ok ok, let's shorten this story up.

Put everything back together, (new head gaskets/etc.. everything that was needed) start it up (sort of hard to start, but not too bad), and it immediately jumps to 3000 rpm and stays there. (after tapping the gas and tapping on the IAC and other things it just stays at 3000). We recheck everything we can, everything looks fine, throttle isn't sticking, etc. We've started it up probably 50 times and it does the same thing every time.

Question for the house is.. What is my problem!?

I've taken the IAC off, switched the key on, and the shaft opens then shuts once. I read somewhere that it is supposed to open and close twice, but that doesn't make much sense seeing as it does it once. (it must not be stuck open, right?) I've taken the one off of my 4.0 Explorer and put it on, and it didn't change anything. (that was a longshot, but it has the same plug and everything, so i tried it.)

I've unhooked one end of each vacuum line and capped it, in order to eliminate it being a vacuum problem, and it started and revved the same exact way.

Not sure where to go at this point.. sorry for the long post, I feel its needed (maybe more, if so, tell me what).

I need this thing to drive soon! Thanks!

(If I like this place, i'll definitely stick around as I have already done with F150Forum.com since 2010!)

Anyone have any ideas? We are still stuck.....

Sure you got the new intake gasket in place correctly? Could be a vacuum leak there. You didn't by chance move the TPS when you had it apart?

Throw a vacuum gauge on it and let us know the results.

Did you unplug the IAC while it's running? If it's working it will die....that don't mean it's working right,just that it's doing something lol +1 to using a vacuum gauge and checking the TPS if ya moved it.

The new intake gasket is in place correctly, with goop between the two heads along the front and rear like its supposed to have, everything is tightened down to spec.

Never touched the TPS. Bought a new one this morning, put it on, it has no effect. Gonna take it back once we get this thing fixed.

I have took the IAC off, started the truck up, and it does the same exact thing. I have left the IAC on the truck, unplugged it, and it does the exact same thing. I bought a new IAC this morning, put it on, and it does the exact same thing, gonna take it back too after we're done. (Took the old one apart, shaft moves great, pretty dang clean.)

I really don't want to have this thing running for a minute to check the vacuum, lol. 3000+ rpm on a cold motor isn't any fun!

Is that the next step though, to check the vacuum?

Well I hooked up the vacuum gauge, fired it up, and it was reading 25 in Hg before it finished revving up (got to 3500, had to shut her down lol). That tells me the vacuum is good, right?

I literally don't know what to do/check next. This doesn't make sense to me.

Anyone else? Throw a hail mary, I'll listen.

Ok y'all.. she's fixed! You're gonna laugh at me when you see what was wrong.



I've looked this thing over a million times but never saw that the #2 intake port gasket was only halfway in! One side of it slipped out when I was tightening it down, and it is in a really hard spot to see.

Thank you all for the help, and I will see you guys around on the forum cause I'm sticking around for sure. Some great threads in here.

... 3M spray adhesive.

Glue em in place. It doesn't effect the seal, makes it better if anything. I can't afford to make a time consuming mistake like that, it use spray adhesive or RTV, and glue down almost every non-studded gasket I come by.

You fixed it. You didnt jump to the conclusion that something else had broken and started to throw parts at the problem. I am a humble hacker. 5 decades of breaking stuff, has taught me where to look after something I just fixed doesnt work.

Glad you got her fixed... Don't ask how I knew you had a problem with the intake gasket... I'll never tell.

Well?....how's it run? lol Vacuum reads a little screwy on these....will appear low at idle but raise the rpms just a hair and it will jump up,then fall as the rpms get higher. Mine checked at around 20 which aint too great but I put Restore in it and raised it to 22-23. My truck shows 183K but I'd guess it was rebuilt or the heads replaced at some point cause under the valve covers it's clean...really clean. I always use RTV on one side of gaskets to hold em in place...sucks fixing something twice.

Yeah great idea about some adhesive to hold the gaskets temporarily.. never thought about that. Haven't checked the vacuum yet now that it is running correctly.

It runs just about perfect. We haven't set the timing and it has very bad gas in it, and this is the first time its been over 2 mph in over a year. So if it runs this good now, i can't wait until tonight when we finish


Just some history on it if anyone cares.. I am the third owner, first was my friends grandpa and he gave it to my friend a few years ago. Has 86xxx miles on it, and I highly doubt that is 186xxx. The thing is almost a time capsule if you look under the truck, its just about perfect. Not a speck of rust anywhere. It's just gonna be my daily driver, and following the tradition with every other vehicle I own it will be improved upon from what it is now, to my tastes.

I have a 9th gen F-150 which is lowered 3/5, and i'm building a 460 to drop in it. I also have a 8th gen F-150 with a 351 (keeping the 351) which I am doing a 8 lug SAS on currently, with a '78/'79 Dana 60.

See you guys around here on the forum, glad to be here. Not planning on modifying the ranger any other than when stuff breaks, trying to save some gas and fall in love with another truck. (oh gosh no... lol)