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2004 gmc envoy_slt
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Discussion Starter · #1 ·
I peroidically/ regularily get this code( P0455 Evap Emission Control System Leak (Large)) now. Most of the time the code clears itself after a day or so but lately it seems to be staying on longer and coming back more often after I clear it. Just a while ago I got a P0172 System to Rich Bank1 code instead though.

The issue that I am encountering with my vehicle at the moment is an unresponsive throttle at highway speed. When the throttle turns unresponive all I have to do is pull over and wait about 5 min then take back off like nothing happened. The vehicle still idles though and can attempt to rev up the engine but after about 500 rpm advance drops back to idle. The only time this really happens is over long distance trips. About 2 hours ish.

Doing some investigating and talking with some people the reason for this could be due to the drive cycle needing that much time to fully cycle. I am thinking I am getting a vaccuum loss when the Purge Solenoid opens to purge the Evap canister of its gases and thus staying open too long causing my throttle body to protect itself from thinking its stuck by reducing rpms to idle. How the Rich code came about I feel that the solenoid may have stuck closed too long resulting in to much vapor entering the system.

I am not sure which to replace at the moment, the Solenoid or canister. Both seem to be fairly cheap though. Another question I have is isn't this supposed to be protected under a Federal Emissions Standard for the first 100k miles? An advice would be appreciative, I will post the verdict regardless though.

P.S. I like the site, good to see some many posts and nice to find so much info and help for us people who do things outselves! I have a DTS freeze frame of both of those codes thrown I will post for some of the more knowledgeable people who know what the info means

P0455 P0172
Trottle Position 14.1% 31.3%
Engine RPM 616 1809
Load value 38% 77.6%
MAP Sensor 39 kPA 59 kPA
Coolant Temp 185 deg F 185 deg F
Intake Air Temp 78 deg F 77 deg F
Ignition Timing Advance 15.0 deg 32.5 deg
Commanded Secondary ATMOS
Air Status
Short Term Fuel Trim1 -6.3% .7%
Long Term Fuel Trim1 -10.4%
Short Term Fuel Trim3 -32.5%
Long Term Fuel Trim3 -82.5%
Vehicle Speed 0 mph 62mph
Fuel System1 CLSD CLSD
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