95redv6stang

I'm new to GT's

My car recently threw a CIL with P0456 which is a fuel vapor leak or lack of purge flow in the EVAP control system.

I'm aware that it may be my gas cap or a leak in the vacum system... My car is a 2003 GT 5 speed 60k miles and completely stock.

My main question is, when my car is in neutral or the clutch is pressed in my car wants to hold at between 1400-1600 RPS for about 5-6 seconds. Would/Could these problems be linked or is this problem elsewhere?

Is this a common issue with the 4.6's?

And how do I fix it?

Thanks for you help, Chris

Sxynerd

Google FTW. Search took .001 seconds

P0456 (Evaporative Emission Control System Leak Detected (small leak))
Can be an internal (leak into the engine system) or external (into the atmosphere). Examples of some external system leaks are: a loose gas cap, a disconnected evaporative system hose, or a loose hose connection.
Internal leaks can be caused by a stuck open Duty Cycle Purge (DCP) valve Check under the hood to make certain no vacuum lines are disconnected, check your fuel cap if it isn't sealing correctly or is missing or the wrong one this will cause that code to set, You may have a bad vent valve causing the problem. What this code means is that the computer has tested the evap system and was not able to draw a vacuum on the fuel tank. it does this by turning on the evap vent valve which closes the fuel tank vent off, It then opens the vacuum solenoid and allows engine vacuum to be drawn on the fuel tank. A sensor in the fuel tank monitors the Pressure/Vacuum levels on the tank and reports this to the computer.If the computer does not see a change in pressure/vacuum on the tank then code P0455 will set.

WhiteFoxGT

Reading comprehension FTW

He said he knows what causes the code, but wanted to know if his high idle problem could be related..

Anyway, I believe the culprit could be the IAC.. Do a search on the boards for the "IAC mod"

Sxynerd

Oooo burn!

95redv6stang

Lol. Thanks. Yeah, I was thinking IAC or I also heard of the PCV causing this?

Sxynerd

I got served, lol. But, A vacuum leak can cause the high idle, which was my point. Along with the IAC which everyone jumps to most frequently, have you add a Tb/Plen or headers to the car? If you reset the Learned Mem and delete the code off the ecu, does it still do it?

grogan

does it hold at 1400 to 1600 then drop down to 900 or so? to change that u can take the gasket out of the iac and cut the 2 holes out of it to make 1 bigger hole. it wont pass emissions but it would do that anymore.

cliffyk

Here's what the '03 shop manual says about P0456--no mention of IAC, however leaks in the EVAP system can cause wierd idle problems....

95redv6stang

Well, I was reading today and I read it will eventually throw a P0442 which means the problem has not been solved and... shure enough it did. So, I replaced the gas cap to hopefully stop the CEL.
BUT, I still can't figure the idle. I'm thinking that on sunday I will clean the IAC.


The car is BONE stock. No mods of any form of the car as we speak. I was thinking about the vacum leak and that is on my list of things to check. All I have done is deleted the code when it pops up. (once with P0456 and once with P0442)

Sxynerd

I wish people took me more seriously.