Idleing/reverse problem? Help!

hey guys. sometimes when i start my truck up, it slowly revs up, like its about to die, but then idles fine. then if i throw it in reverse and press the gas, it drops to about 100 rpms, and when i let off it revs back up. it does this about 3 times till it stops doing it. any idea what it mite be?  

Aubie,

What year/make/model truck? Any modifications done? Give us some more info and we will try to help!  

ive got a dual exhaust system i did myself, and a K&N replacement filer. thats it for right now. it quit doing this idleing problem when i replaced the filter, but then came back few weeks later. it just almost dies, runs again, almost dies. only in reverse tho  

and its a 2000 gmc sierra SLT. 5.3L V8  

could it mabe be a fuel pressure problem?  

yes.... if your fuel filter was clogged when you removed it... it could have clogged again...

remember.. the fuel filter is in a loop system... the fuel passing through again and again... as the pressure is controlled by the pressure regulator.. excess pressure is returned to the tank...

if you have dirt in the tank... the filter will clog again....


when you take the filter off... use care not to loose the Orings on the end of the tubes or pick up new ones...

but .. try to get a foot or so of 7/16 fuel line.. shove that over the pump end of the fuel filter supply line..  have somebody cycle the key on while you hold a clear plastic 2 liter bottle to catch it.. the pump will only run for 2 seconds....   examine the fuel ... got dirt.... stick a magnet against the bottom of the bottle.. does the dirt attract to the magnet???  if so.,...   find an old speaker...  pry the magnet off it... stick the big magnet to one of the straps...  if your tank is plastic.. it will attract the rusty debris in the tank to the magnetic field..  reduce the amount of fuel filter changes you have to do.

one thing to be prepared for... fuel pump failure...  when the filter becomes clogged... the pump is deadheaded..  building MAX pressure...  this shortens the pump life... burns out the brushes... burns the commutator..  it will get to a point where it many not start spinning... at that point.. the truck won't start..

you can almost always have somebody crank the engine while you pound hard on the bottom or sides of the tank to bump the hard enough for it to start a time or two more...   knowing that will save you a tow...


you probably will also want to throw a scan tool on the truck.. see if any codes have set...

post any codes you get...