Fast Idle

[Sand Flea]

Greetings All,

I am new to this forum and I am also new to owning a Bronco. I just inherited a 1987 full size Ford Bronco. It seems like a good solid vehicle and only has 90,000 miles on it. I intend to use it on the beach for some fishing. I just got it legal and took it out for a drive and found a problem that I was hoping someone here may be able to help me with. When the motor reaches normal operating temperature and I press the accelerator the idle speed jumps up to (2500) R P M's and stays there. If I shut down and restart the motor it starts the same process all over again. It Idles fine until I press the accelerator. Help with this matter would be greatly appreciated. Thanks

 

[monzo]

Greetings All,I am new to this forum and I am also new to owning a Bronco. I just inherited a 1987 full size Ford Bronco. It seems like a good solid vehicle and only has 90,000 miles on it. I intend to use it on the beach for some fishing. I just got it legal and took it out for a drive and found a problem that I was hoping someone here may be able to help me with. When the motor reaches normal operating temperature and I press the accelerator the idle speed jumps up to (2500) R P M's and stays there. If I shut down and restart the motor it starts the same process all over again. It Idles fine until I press the accelerator. Help with this matter would be greatly appreciated. Thanks

might be far fetched but does it do it after it rains or moist weather or does it do it all the time?

 

[Sand Flea]

might be far fetched but does it do it after it rains or moist weather or does it do it all the time?

It does it all the time.

 

[BroncoJoe19]

guesses?

carpet resting on gas pedal?

Sticking throttle cable? or linkage?

 

[dashwitz]

I have what im assuming is the same problem. She runs great right up until high idle, then has a mind of her own. I have a 91 Full size w/ 302 and for the most part the truck is gutted and getting ready for some new floors. However, thats besides the point. i have removed the air intake pipes and airbox/filterbox and took off the radiator to convert it to electric for just a bit extra cooling power. however once i put the cooling all back, i discovered that since the air hoses had not been reinstalled yet, i could hear the IAC giving the motor bursts of air... seemingly when it did not need them. pop off your air hoses to the throttlebody and fire her up and listen for the IAC giving the motor a bit more air when the high idle occurs. it sounds like one of those compressed air cans your clean out your keyboard with.

also, it just occured to me, my motor is running a bit rich and you can smell the unburned fuel after it hits the weird high idle, does this happen for you too? not sure if its a related issue or just another problem i need to get too.

i have replaced:

IAC

plugs/wires

all rubber air hoses

i will be replacing

map sensor

o2 sensors

Hopefully, if it is the same problem im having, we can figure this one out together... im stuck at the moment.

~nick

 

[BroncoJoe19]

A few things that can cause a high idle are:

vacuum leak/s

and faulty TPS.

I'm not sure about the IAC causing a high idle, a bad/sticky IAC can cause a crappy idle for sure.

TO help narrow it down, one can pull codes.

What does the IAC do? How does it work?

Ford Fuel Injection

 

[Sand Flea]

Thanks to all for the info. The vehicle set for a while before I picked it up and I thought it may have been bad fuel. " simple things first" I waited until it was low on fuel and put some fuel injector cleaner and some fresh fuel in it and drove it about 50 miles and the high idle problem seems to have cleared up. Now it is hard to start and idles to low. It shuts down when I stop at a light. I am going to run the fuel I have in it now to about 1/4 of a tank and see if it gets any better or if there is any change. Then I will pursue some of the suggestions you all have recommended. I have checked for vacuum leaks by sight, sound and carb cleaner and have found none. I will check out the sensors and the IAC after I am sure it is not the fuel. And to dashwitz, yes when the idle jumped up it was definitely running rich and I could smell the unburned fuel. Thanks again to you all for the input.

 

[dashwitz]

ok so i just stopped back at my garage. I wanted to grab a quick video of what the truck is doing as far as the idle situation. Both these videos are without me for the most part touching the gas pedal at all. Please take a look and tell me what you think. Sorry about the poor quality, all i had handy was my phone

 

[zookeeper]

might be far fetched but does it do it after it rains or moist weather or does it do it all the time?

Just out of curiosity, what would cause it to idle REALLY high after it rains or in moist weather? My 94 does that if I run through a big puddle or when I run it through a drive thru car wash.

 

[dashwitz]

i wish it were that easy for me... unfortunately mine does it all the time, i currently have the truck up on jack stands in my garage... no water in there if anyone can point me in the right direction for my issue, i started my own topic on the forum to unclutter sand flea's topic

THANKS!