Need help with P0455 Code
08-23-2018, 06:56 PM
#1
Instructor
Thread Starter
Need help with P0455 Code
OK, I need some help with this P0455 code that recently came up on my 1999 Cab C4 manual with 130,000 miles. I just recently replaced all 6 coils, spark plugs, and all 4 O2 sensors. Coils had never been replaced before to my knowledge. It took me a few weeks to get all this done because I had to wait for parts and it being hotter than hell so I took my time. I also had taken off the mufflers for easier access. Around the time I was almost finished, I was looking to replace the brand new Stant gas cap with an OEM because the OEM cap has the rubber string thing so you don't accidently lose your cap. I undid the cap and noticed a woosh sound. Didn't think too much about it but thought it was odd. Obviously, the Stant gas cap is doing its job and sealing well.
However, this morning on the way to work the check engine light came on. Drove the car about 500 miles this weekend up to Dallas and the car ran fine. However, I noticed a few odd things that I ignored thinking it was my imagination:
1. At idle, the engine idles perfectly regardless of whether the AC is on or not. No surging or up and down. But occasionally the engine makes a kind of loopy sound. Kind of like it is cycling in a loop and not linear. Sounds like a slow rum, rum, rum. Not sure if I am describing this correctly. Basically the idle is not constant sounding. It does this occasionally obviously when I am at a stop/idling and then will go away.
2. A couple of times I noticed a gas smell in the cabin on the freeway. I thought this had to be my imagination and that I was smelling either another car in front of me or it was the car fragrance the previous owner had sprayed in the car. It's funny how we try to justify that something is your imagination and that it couldn't possibly be what you think it is. And today on the way back from work, I smelled gas again but this time only briefly. Car still ran fine on the way home.
3. I can hear some weird slight thumping/tapping sounds on the right front dash area. At first I thought it was the speaker acting up or the flex from being a cabriolet was causing this noise. But now I think it is related to the fuel filler opening as this is where it is located.
Drove home all worried and thinking about what the hell could possibly be wrong and maybe I put the car back together wrong. Ran the OBII scanner and came up with P0455. I've done some research on the forum and it looks like it is fuel/vapor related. Opened the gas cap after I got home and this time made a wooshing sound for about 10 seconds or so. Obviously the gas cap is sealing correctly. I used to have a 968 that had this similar wooshing sound when the gas cap was undone. The car would stall when driven for awhile. So I kept the gas cap loose and the car never gave me problems after that. And that's what I've done with the 996 but want a permanent solution.
I just purchased:
996-201-143-01-M100 Fuel Tank Vent Valve on tank
996-605-203-01-M244 Fuel Tank Vapor Valve for carbon canister
I'm assuming both of these are not hard to replace. For the fuel tank vent valve I guess just remove the fender shield?
Not sure about how to replace the vapor valve for the carbon canister. Where is this located and easy to replace?
Any ideas on what could be the actual problem or advice would be much appreciated. Man, every time I think I've got this car all sorted out, another problem crops up. It's a never ending quest.
However, this morning on the way to work the check engine light came on. Drove the car about 500 miles this weekend up to Dallas and the car ran fine. However, I noticed a few odd things that I ignored thinking it was my imagination:
1. At idle, the engine idles perfectly regardless of whether the AC is on or not. No surging or up and down. But occasionally the engine makes a kind of loopy sound. Kind of like it is cycling in a loop and not linear. Sounds like a slow rum, rum, rum. Not sure if I am describing this correctly. Basically the idle is not constant sounding. It does this occasionally obviously when I am at a stop/idling and then will go away.
2. A couple of times I noticed a gas smell in the cabin on the freeway. I thought this had to be my imagination and that I was smelling either another car in front of me or it was the car fragrance the previous owner had sprayed in the car. It's funny how we try to justify that something is your imagination and that it couldn't possibly be what you think it is. And today on the way back from work, I smelled gas again but this time only briefly. Car still ran fine on the way home.
3. I can hear some weird slight thumping/tapping sounds on the right front dash area. At first I thought it was the speaker acting up or the flex from being a cabriolet was causing this noise. But now I think it is related to the fuel filler opening as this is where it is located.
Drove home all worried and thinking about what the hell could possibly be wrong and maybe I put the car back together wrong. Ran the OBII scanner and came up with P0455. I've done some research on the forum and it looks like it is fuel/vapor related. Opened the gas cap after I got home and this time made a wooshing sound for about 10 seconds or so. Obviously the gas cap is sealing correctly. I used to have a 968 that had this similar wooshing sound when the gas cap was undone. The car would stall when driven for awhile. So I kept the gas cap loose and the car never gave me problems after that. And that's what I've done with the 996 but want a permanent solution.
I just purchased:
996-201-143-01-M100 Fuel Tank Vent Valve on tank
996-605-203-01-M244 Fuel Tank Vapor Valve for carbon canister
I'm assuming both of these are not hard to replace. For the fuel tank vent valve I guess just remove the fender shield?
Not sure about how to replace the vapor valve for the carbon canister. Where is this located and easy to replace?
Any ideas on what could be the actual problem or advice would be much appreciated. Man, every time I think I've got this car all sorted out, another problem crops up. It's a never ending quest.
08-24-2018, 09:59 AM
#3
Instructor
Thread Starter
So this is the valve near the throttle body correct? Do you know the part number? And what does this valve do? I read the thread and it really helps.
Thanks so much.
Thanks so much.
