[broncosbybart]

My bronco idles high when warm. When it starts (cold) it runs fine. As it warms up, the idle stays high, almost like on a carb with the high idle cam sticking. i can put it in neutral and give it a quick tap on the gas it will come back down to a normal (700-800rpm) idle and stay there until it is moving again. it usually idles around 12-1500 rpm otherwise. it never has run properly since i've owned it. i've replaced the tps, map, hego, tuned it up, replaced the fp reg, and egr. it runs good now except for that issue. i haven't replaced the intake air or coolant temp sensors or the (i forget the name now- i think it is the bypass air valve). it isn't throwing any codes at the moment... thanks.

 

[waltman]

So in other words, you threw money at it and hoped one of those components would fix the problem. Get a repair manual and start by looking for codes and then you might want to remove your IAC and clean it and also, using your manual check to see that it is OK.

 

[CrazyBRONCOguy]

Mine had a vacum leak that caused it to do the same thing.
Also you might want to check the gasket between the upper and lower plenums, my fathers truck had the same prob caused by that being bad too

 

[95_G&W_XLT]

Did you perform a KOER test? If you only did the KOEO, you might not be getting all the information the computer is holding.

 

[Gacknar]

i can put it in neutral and give it a quick tap on the gas it will come back down to a normal (700-800rpm) idle and stay there until it is moving again.

The throttle is sticking slightly open.
Crank it up and get the high idle going.
Open the hood and grab the TB lever and close it. The idle will drop.

Now all you have to do is find out what is keeping it from resting all the way against the set screw.

 

[waltman]

Sorry, I didn't read the last part about you checking for codes. Clean the IAC, the thingy on the side of the throttle body. Those are notorious for getting gummed up.

 

[Gacknar]

Clean the IAC, the thingy on the side of the throttle body. Those are notorious for getting gummed up.

It's not the IAC, It's the throttle plate stopping before it hits the set screw.

Thats why bliping the throttle real quick will fix it untill you touch it again. The faster momentum couses it to shut all the way where realeasing it slowly lets it stick just before closed.

 

[broncosbybart]

ok guys

yeah, i blindly threw a bunch of money at it... i don't go about guessing. believe it or not, all of those things replaced were bad on the vehicle. it was a wonder that it ran when i got it. i've had the tb off of it when replacing the tps- it works smoothly and i cleaned it while it was off. i am now running into a point where i'm not sure what is wrong and thought maybe someone else out there had a similar problem and found out why. i appreciate your input, but remember, there are still a few people out there that actually know what they're doing and aren't afraid to ask for advice when needed.

 

[broncosbybart]

i must thank the crazybroncoguy. a vacuumm leak could very well be it. i haven't noticed anything obvious but am going to do some further investigation. i will also look at the throttle plates, too.

 

[Gacknar]

Do the test I told you.

Somthing is keping the throtle plate from resting against the stop screw.

Trust me on this.

I spent 4yrs when I was a dumb a$$ teen tracking this down.

I know the simptoms.

 

[JVHBRONCO]

A CAN OF STARTING FLUID TO SPRAY AROUND THE INTAKE GASKETS. IF IT REVS UP THATS YOUR LEAK.IF IT DONT... CHECK YOU THROTTLE CABLE AND IDLE ADJ. TO MAKE SURE THE THROTTLE BODY IS CLOSING PROPERLY.

 

[MikE2]

My truck does the same thing, and I still havn't found the problem yet. Only thing I have found out is the engine idles and runs great with the TPS unplugged

 

[Gacknar]

A CAN OF STARTING FLUID TO SPRAY AROUND THE INTAKE GASKETS. IF IT REVS UP THATS YOUR LEAK.IF IT DONT... CHECK YOU THROTTLE CABLE AND IDLE ADJ. TO MAKE SURE THE THROTTLE BODY IS CLOSING PROPERLY.

STOP YELLING!
thank you :thumbup

My truck does the same thing

If you blip the throttle does it idle back down to normal like his does?

 

[Tommy R]

I agree with Gacknar. That's also about as easy as they come to verify. Once it warms up and idles high, pull over, pop the hood, and see if you can manually close the throttle body blade. If so, pull off the intake tubing and clean the TB out. If the TB is already closed completely, I'd lean towards a gummed up IAC. Regardless, checking codes would be wise.

FWIW, my Mustangs would do this exact same thing. One of them needed the TB cleaned up every few months.

Tommy

 

[hipropos]

You may want to remove the throttle cable and cruse control cable, and start it. Sometimes the cables are sticky and keep the it from closing all the way up. I had this problem on a old ranger 2.9 fuel injected. If it is the cable there is several fixes for it, but the best is to just get a new one.

 

[MikE2]

STOP YELLING!
thank you :thumbup

If you blip the throttle does it idle back down to normal like his does?

no. Shifting is a bitch too because when I let off the gas the RPM's just hang around 3000 or so. And sometimes it idles at 1000, sometimes 1400, sometimes 700.

 

[bigjhoov]

:banghead

 

[Gacknar]

no.

Then you dont have the same problem he does.
Yours is somthing else, his is the throotle blade sticking.

 

[84broncorig]

Mine had a vacum leak that caused it to do the same thing.
Also you might want to check the gasket between the upper and lower plenums, my fathers truck had the same prob caused by that being bad too

i had the same prob, the gasket was in peices...i would press the clutch to neutral and it would ideal at 2000 or higher...it sounds like a pain in the ass but it is a important thing to check....u will need a T40 or T45 long stem wrench for the middle nut...i can't remember...hopefully some other pros can help me out there...but that sounds like the prob to me:rebelflag

 

[bigric]

If it's simply a matter of the throttle not returning all the way to the stop screw, just throw another spring on it. My TB wore out (bushings? springs? who knows) and so I just hooked in a carb return spring and all is good.

You can see where I anchored it to the throttle body and then to the throttle cable bracket.