dropping rpms

[redranger02]

after my truck warmed up. it idles about 600 to 700 rpms. but every few seconds the idle will drop somewhere around 450 to 500rpms for a split second just enough to notice. it does it most of the time when im in park. but it has done it while i was in drive a few time. has someone come a cross the problem before and how did u fix it. thanks


02 xlt 4.0 sohc

 

[RangerMan64]

I am having the same problem here man. I don't know what is going on. I don't know if your's does this or not, but when my ranger drops below 500 RPM's, the oil pressure light flickers.

 

[Big Jim M]

Is the AIR CONDITIONING on? Could it be from the a/c cycling?
Big Jim

 

[scalrngr]

Mine was doing that a while back, turned out to be a vacuum leak. The fuel rail to upper intake gasket was bad. Have someone watch your RPM while you spray some carb cleaner around your gasket and see if the RPM jumps up.

 

[dogboy]

Mine did this a while ago at stop lights and what not (when I would stop at the light it would sometimes drop the idle to around 400-500 (almost dieing) but would come back up after 5-10 seconds, and since the plugs probably needed to be changed anyway, I went ahead and changed the spark plugs and I haven't seen the problem since.

Hope that helps.

 

[redranger02]

yeah i thought it was the plugs to so i change them. it helped a little but it still does it sometime. no the a/c is not on.

 

[mikebboy]

I have a very similar problem... when the engine is warm and I throw it in Park the rpms drop below 500, sometimes stalling.

I have a couple ideas that I will check and let you know if I figure it out. They could be related.

 

[lhc_cj7]

Had the same issue with the wifes expedition. Two things; the vacuum hose on the back of the throttle body had a hole and then the IAC went bad.

my 2 pennies worth

 

[RangerMan64]

Well my truck is in dire need for a tune-up anyways, so I will probably do that in the near future. Will also check for vacuum leaks. Thanks