Rough Idle

[buckinbronk]

When I start up the bronco it will idle from 1000 down to 500 then will jump up again then down again. Then maybe awhile later it will level off at 1000 but will soon go back to the weird idleing. Another problem is when goin down the road at about 35mph or so I will give it a little gas and the truck start to hesitate and rattle a little. Whats the problem, and are they related?

 

[BLADE262US]

2 things to check cause mine was doing the same thing . The EGR valve located on the passenger side front of motor may be clogged up or rusted shut as mine was . Check that first . Then the idle air motor located on drivers side front of intake bolted to the throtlle body may be gummed up or non functional . ( note on the Idle air control motor , These are a bit expensive $60 bucks at advace auto and the new ones dont work on the old ones . I took one off a 96 trying to figure out what mine was doing and it would start then die later found out from a friend that works at ford that they decided to put a diode in the valve so when you replace the idle air control motor if this happens to you start and die , you must take plug on wire harness apart and swithch the 2 wires around then it will work fine . Let me know what happens

 

[Seabronc]

I don't recall seeing the year of your truck mentioned, is it EFI or Carb?

>-

 

[buckinbronk]

It is an 87' full size bronco EFI.

 

[sweepersrgr8]

I would check the items Blade mentioned, but also the TPS voltage, the TPS could be loose, or worn out, and will cause eratic idle problems.

Your Chiltons manual will outline all of these procedures.

 

[buckinbronk]

Im not familiar with a TPS. Where can I find it and how to I check it.

 

[Seabronc]

TPS = Throttle Position Sensor. You realy need to get a Chilton's or Haynes manual or both. They will be a big help to you. Most auto parts stores carry them, you can also find them in book some stores.

Good luck,

>-

 

[sweepersrgr8]

The TPS is located on throttle shaft, on the bottom of the throttle body. It will have 3 wires coming off of it to a round connector. Right off the top of my head, I think they are orange, green, and black/white stripe.

 

[sweepersrgr8]

P.S. I had to go check the Haynes.

Pick up a Chiltons, or Haynes manual at you local autoparts. I think you may have to order the Chilton's (I did), it goes into more detailed repairs, and gives OE part numbers, so get one. The Haynes does outline the procedures for troubleshooting the EGR, ICS, and TPS in good detail. So pick one up if Chilton's is not available, cause that's too much to type. It's fairly simple, and you will learn about your truck.


Hey Seabronc...didn't think a Carb man would know what a TPS is.

 

[Seabronc]

I saw one once / :-"

>-

 

[cowboydan]

i got a cool fathers day gift(my wife not knowing a thing about cars/trucks). she got me a chiltons manual on cd!! easy to install and can be used for ford truck from 76-00. only catch is that you have to buy different codes for different trucks.