[Ranger3.04x4]

Hey guy's I have a question about my 99 Ranger 3.0! My problem is after I have driven my truck for a long period of time or have been driving it pretty hard when I put it in park or neutral the revs will jump up to 1500rpm's if I give it a little throttle it will drop down to around 800rpm's and not go back up. It's acting like the throttle is sticking but I don't believe that's what's happening. Also if I turn the A/C on while it's at a high idle the rpm's will drop down to about a 1000 but as soon as I turn the A/C off it will jump right back up to 1500rpm's. My check engine light has been on for about a year now but the problem hasn't occured until about three months ago. I don't remember what code is getting thrown with the light but the local mechanic is saying that a vaccum line is unplugged somewhere around the (CHARCOAL CANNISTER) I have no idea what that is or where but he took a look at my truck and couldn't find the supposedly disconnected hose! Sorry for the long post. Thanks for the help!

[OTRtech]

Try cleaning the IAC on the throttle body.It's a common problem with idle issues.
As for the vaccum problem,between the canister and the manifold is a valve and a switch mounted in the line.The valve (solenoid) sometimes sticks open.The switch detects whether or not vaccum is present in the line.
The valve only opens for a minuite or two to pull gas vapors from the canister when you start the truck.
If it sticks open you'll get a light and code.
I've had good luck sometimes removing the valve and rapping the top of it against a block of wood a few times to get it unstuck.


Oh and welcome to the forum!!

[Ranger3.04x4]

Thanks for the info! I will try cleaning the throttle body and the sensor!

[Ranger3.04x4]

Well I went this morning to a local mechanic shop and had the Diagnostic Computer hooked up to see which code is being thrown on my idiot light and this is what it said! P0455 Evap System Gross Leak Detected! Can you guy's help me out on what this means! Thanks!

[Interceptor944]

P0455 - EVAP Control System Leak Detected (No Purge Flow or Large Leak) The PCM monitors the complete EVAP control system for no purge flow, the presence of a large fuel vapor leak or multiple small fuel vapor leaks. The system failure occurs when no purge flow (attributed to fuel vapor blockages or restrictions), a large fuel vapor leak or multiple fuel vapor leaks are detected by the EVAP running loss monitor test with the engine running (but not at idle). After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications
Disconnected or cracked fuel EVAP canister tube, EVAP canister purge outlet tube or EVAP return tube
EVAP canister purge valve stuck closed
Damaged EVAP canister
Damaged or missing fuel filler cap
Insufficient fuel filler cap installation
Loose fuel vapor hose/tube connections to EVAP system components
Blockages or restrictions in fuel vapor hoses/tubes (items also listed under disconnections or cracks)
Fuel vapor control valve tube assembly or fuel vapor vent valve assembly blocked
Canister vent (CV) solenoid stuck open
Mechanically inoperative fuel tank pressure (FTP) sensor
Check for audible vacuum noise or significant fuel odor in the engine compartment or near the EVAP canister and fuel tank

Look for a broken, or disconnected vacuum line if was me first.