My Girl Friend just purchased a 1986 Bronco II 2.9V6 4X4 and it idles ruff like it will sound like its loping or like I'm tapping the gas and then when I'm in drive its runs great until i start to break then the trucks RPMs go almost to like 600 when i come t a stop but if i give it a little gas she goes back to about 1200 does anyone know how i could fix this problem?

 

First, what you need to do is pull codes (tech info - read first has a procedure or spend the $30 on one of the equus/actron readers). That will more than likely tell you what is going on, if anything. Outside of that, it could be the idle air control needs cleaning, could be a faulty MAP sensor, could be a vacuum leak, could be the PCV valve, could need a tune-up (plugs, wires, cap, rotor, timing, filters), could be the air charge temp sensor, could be the fuel pressure regulator is going bad, could be a fuel filter (there are two), could be the throttle position sensor, could be the injectors (clogged/dirty/loose wiring), could be the EGR valve / sensor, could be a worn camshaft and/or timing chain, could be a leaking gasket and/or dirty intake/throttle body. These are just possibilites, but without pulling codes, you'd wind up spending a small fortune on parts replacement and maintenance and still not know for sure which part was faulty. I would first start with checking all the wiring connections and vacuum lines under the hood, testing all the sensors (read first - tech info at top of forum has procedures) and pull codes. Could just be that the Idle Air Control and intake / throttle body are really dirty (a known issue on the 2.9), but without checking everything out and pulling codes, no way to pinpoint one or multiple faults.

 

alright thank you how would i pull the codes?

 

Go HERE and scroll down to "Pulling EEC-IV codes". It is a link to an Adobe .pdf file that explains how to pull codes without a code reader. You can also go to just about any auto parts store and pick up an Equus/Actron (Actron CP9015, Equus 3143 or 3145) code reader that will work for about $30 which simplifies things. The Equus 3143 and Actron CP9015 are identical, if I remember right, and the Equus 3145 (which is what I have) has a digital readout which makes things really simple and you don't have to count the number of light flashes. All of these scanners listed above come with operating instructions and a list of all the codes and what they mean, if I remember right. If not, then the codes are listed in the link below "Pulling..." and on TRS (therangerstation.com) in their tech library. Hope this better answers your question.

 

thanks for the help

 

Try the basics first and do a compression check. When a bad cylinder is operating it will give you a somewhat rough idle, but smooth right out when cylinder pressure( not compression) goes up with more feul/air mixture arriving at higher rpm everything kind of evens out and your driving on a cloud... to a point. Pull to a stop and its idling rough again.

Pull your spark plugs and look at each one for oil or soot. Soot would be a fuel related issue or white chalky is to lean and oil...well, bad cylinder.. rings or valves. Ongoing blue smoke is usually cracked rings, or excessive black smoke, ( an overly rich condition from the exaust) is a good hint of problems with fuel as well. billowing white smoke is way to much fuel, its drowning in it.Hope this helps