2.3L ('83-'97) 1997 2.3 excessive idle speed continues after IAC replaced

[Sidecar Doug]

My 5 speed Ranger has been showing intermittent check engine signals - they go away, then return, sometimes after a couple hundred miles, sometimes after just a few miles. I need to pass a smog test to re-regiister, and the light would not go away- the code on my scanner was for excessive idle speed. I checked the connection to the IAC, and they seemed OK, so I replaced the idle air control solenoid with one from NAPA. I then erased the codes on my scanner and started the engine, letting it idle in the driveway for about 15 minutes ( 37 degrees F outside temp. ) I saw that there was a code so looked it up and it was for excessive idle speed. Any thoughts on where to look next for a solution ?

 

[franklin2]

When you get it fully warmed up (upper radiator hose hot) and idling in the driveway, unplug the connector on the idle air control solenoid. What does the idle do? It should slow and almost stall out. If it just keeps idling high, you have air coming in from somewhere. Look for any hoses missing, or any hoses that may be cracked, squeeze any vacuum lines and look for any that might be split.

 

[Sidecar Doug]

When you get it fully warmed up (upper radiator hose hot) and idling in the driveway, unplug the connector on the idle air control solenoid. What does the idle do? It should slow and almost stall out. If it just keeps idling high, you have air coming in from somewhere. Look for any hoses missing, or any hoses that may be cracked, squeeze any vacuum lines and look for any that might be split.

Thanks - will do tomorrow. I took it for a drive, after clering the code. In about 5 miles check engine light came back on- code 1506. I was paying close attention to the tach, and coming to a stop it would speed up to about 2,000 rpm, then evenly drop back to about 1400.. I may have to use the small bottle of propane at low pressure feeding thru a small diameter hose to check for vacuum leaks.

 

[scotts90ranger]

I would check for vacuum leaks or if the throttle stop screw has been messed with, 1400rpm is high for idle, should be like 600... when I had the upper intake off my '97 a while ago to do the spark plugs I forgot the power brake hose I think and it was MAD, didn't run for anything, you might just have a small vacuum hose off somewhere.

 

[Josh B]

My last smog test was with an 87 Ranger 6 cyl, and it didn't pass. I asked a shop what it cost to have it tested and he said $250.00.
I looked over my smog devices and there were 5, all costing around $50.00 each.
I gave it my best guess and bought the 1st one, installed it, and headed back to emissions.
Passed it 1st time

 

[scotts90ranger]

OBD II is tougher than that... but finding the reason for a high idle shouldn't be too hard, either a broken vacuum hose or a bad intake gasket or someone adjusted the throttle stop screw up for some reason... the only other dumb thing that can change the idle is the VSS on the transmission where the speedo gear is I think, that guy can cause the IAC to hold high if I remember right, but you wouldn't be getting that code because that means the computer is trying to lower it...

 

[Sidecar Doug]

Thanks for the tips ! I backed the idle screw off slowly about 2 turns after the truck was warmed up, listening to the rpm level slowly dropping. Checke the tach, backed it off a tad more until it was reading about 850-950 rpm, and erased the codes on my scanner - then drove into town and checked for whether everything was OK ( complete ). All is well !! Passed smog, updated registration.

 

[franklin2]

Someone is always messing with that pesky idle stop screw. You know they have all been messed by now in the engine's life.