HEY,I am a new user and second time Bronco owner.This time I bought a newer 92 Bronco,but there are some problems.First the 4x4 system doesnt do anything.U push the buttons and the rely or whatever it is behind the glove box just clicks,no buttons light up or 4x4 indicator light come on to tell me whats goin on.I tried tapping on the transfer case motor and nothing.Next,the tach does not drop below 2500,the motor doesnt idle that high so is the tach just broke?This thing takes a couple of tries to start up so I looked under the the hood I noticed nice new shiny sensor that was unplugged,it looks like a cylinder on the driver side of the throttle body.I plugged it back in and it started idling at about 3500 and would not idle down so I unplugged it,is the sensor bad or could it be something else.I would appreciate any help and I hope to help out and answer questions for u guys THANX

 

Hi and welcome to FTE! I moved your post to the BIG BRONCO forum. Someone here should be able to help you.

Enjoy the site!

-Matt

 

Ok, for starters, welcome to FTE and the Big Bronco Forum. We will endeavor to get you the most accurate information that we can.

As for the 4WD not engaging, the electronically shifted transfer cases are notorious for eating shift motors. Aside from that check the fluid level in the T-case as well sometimes too little or dirty fluid will cause poor operation. The shift motors are replacable and run somewhere around the $100 mark.

Your start and idle problems are a nit more difficult. The solanoid on the driver's side of the throttle body is the IAC (Idle Air Control) solenoid and valve assembly. They are sold and replaced as one unit... solenoid and valve together. It MUST be connected for the computer to have proper control over the idle and fuel/air ratios of the engine.

Your problem of an idle that is way too high with the IAC connected indicates one of two possible problems. The first would be either one massive or many small vacuum leaks that are allowing too much air into the system and causing the high idle. Time to check all of the vacuum lines including the PCV line at the back side if the upper intake plenum and the brake booster line...these are the two largest vacuum supplies from the engine to other components.

The other possibility is that the previous owner messed with the throttle plate stop screw in the top of the throttle body. The easiest way to check this is to remove the twin intake hoses from the throttle body and see if there is any gap at the sides of the throttle plates. There should be NONE. The IAC allows the necessary air for the engine to idle through a different location in the throttle body so if the throttle plates do not close all the way the idle will be way to high and the computer will have no way to control the idle. If the throttle plate stop screw has indeed been messed with, you will nedd to put it back to its factory setting. Its not a difficult process but it has to be accomplished by following a very exact procedure. Check these things out and if you need to know how to reset the throttle plate stop screw let me know.

 

Thanx for the help everyone.I have put my 92 Bronco in the shop for the idle problems and they cant figure it out.They tested the IAC valves voltage and it was pulling 12 volts which they said means a ground is bad somewhere or its the computer.They cant find any grounds that are bad and they replaced the computer,and still no cure.Does anyone have any ideas or suggestions? thanx bronco b

 

They replaced the computer?! Thats a LAST DITCH in ANY situation with the EEC-IV system! The failure rate is less that 1 percent! Ok, ok, anyhow, did they even pull the codes from the computer? Anything that deals the system that much greif will trigger fault codes. Were ANY of the suggestions that were already mentioned even attempted? Sorry, but the problem is rather routine around here, especially in cases where a new user has ended up with the screw-ups of a previous owner.

By the way, the IAC runs on a 60 hertz on-off frequency so unless they put the IAC circuit on an oscillascope, they can't tell if the circuit is bad or not. The computer changes the airflow through the IAC by changing the frequency and the fact that the engine still ran with the old computer indicates that the PCM (computer) had nothing wrong with it because the IAC voltage IS battery voltage (approx. 12VDC). The computer merely turns it on and off very fast to control the air flow through it.

 

Is the throttle returning all the way to the "stop"? Mine wasn't because of crud in the throttle body and finally because the accelerator cable was causing it to hang a bit. The fact that it sat for 9 months didn't help either.

 

Thanx grey,I got it back from the shop and it is running alot better,the idle problems are fixed.They said it was the ground to the alternator but sometimes it now seems like its missing,it will cut out and the voltage gauge will drop.Could that be a fouled plug or it is still a electrical problem,when it does it nothing else seems to be affected,lights dont flicker radio doesnt skip....so on.

 

Whatever you do, don't take it back to that shop. They ripped you off and lied to you.

Does your tach work? What speed does it idle at? Does it fluctuate or stay steady?

Is the CEL on? Even if it's not, you may have codes stored in there. When was the last time it had a tune-up? If you don't know, get a quality set of plugs, wires, dist. cap and rotor and replace them.