my truck is a 98 2.5l 2wd Ford Ranger
It has a k&N cold air intake flowmaster exhaust.
I just put a new I.A.C sensor,Throttle positining sensor i cleaned the M.A.F sensor,and replaced the throttle positioning sensor.... I don't know what else to do or check.
Your help will be great.
it idles fine but if i start to role with no gas being applied it starts to gain rpms, it will reach about four grand then idle down when you sto rolling.

while idling if you roll on the gas it will bogg down, but if you can get it above 2 its fine

when you come to a re light or stop sign i will gain rpms up to 4 or 5 grand for about 3 seconds then idles down

I can usually figure out whats wrong with my truck but me and some of the mechanics i've taken it to are stumped

 

what about the egr valve? im not sure....

 

thats sounds like what happen to me last week...i took it in and they connected the computer and said that it was either my egr valve or the sensor and sure enough it was he said it is common on rangers 97 and up

 

I have already replaced the EGR about a year ago... you think it could already be bad? I bought it at Advanced Auto Parts. Quess i need to go to the dealer.

 

check pcv valve too...

 

couldn't find it.. where would it be located on a 98 ranger? bottom of the motor?

 

This weekend i changed all the plug wires and four of the plugs... the other side checked out fine. Cleaned the EGR, cleaned the throtle body,and the MAF... it doesn't sputer while going down the road anymore, but can't it can't deside if it want's to idle up or idle normal.

Went to Advanced and let them put if on there hand held computer and it gave me a read out that goes a lil something like this
<Idle air control overspeed error
<Catalyst efficiency below threshold (Bank1)
<System to lean (Bank1)

I was told and even looked it up and " Bank1" stands for(The bank of cylinders containing cylinde #1

Don't know what that means figured i would add that to help you help me

Thanks
SPANKY

 

pcv look down between the first 2 injectors (drivers side of engine)

 

unplug the IAC valve with the engine on. the idle should revert to below 1000 rpms. you can then check the IAC by taking it off and hooking it directly up to 12v.

 

As of right now my truck will not crank at all. So I have been told to try to change my Crankshaft positioning sensor. do you think this would be a good thing to change?

 

normally high idle is caused by vaccume leak.. get ur fuel perssure tested as far as the catalyst effiviency below threshold...could have cloged cat?? (not sure bout that jus an idea correct me if wrong!!!) other than that there arent much to 4bangers