P0401/EGR CEL code seems effected by

[Ramblin Fever]

gas brand in my truck.

Could be coincidental, I'm not sure, but it seems offly funny how when I run Shell 87 octane for weeks and weeks with no CEL, and then suddenly use a different gas station for one tank, the CEL light will come on - immediately after pulling out of the station.

The first few minutes after a new tank of Shell gas, CEL goes off and stays off as long as I keep using Shell.

I chose Shell gas as my primary a few years back, as I'm getting excellent mileage with their gas versus other gas stations - could be all in my head, I don't know, but it's offly funny how this CEL code stays off as long as I have Shell in the tank.

Any ideas? If you look in my past threads on this CEL code, you'll know I've already tried and done everything else, shy of replacing the EGR valve itself.

This time really bummed me too, because it had been off most of the summer - but weird as it may be, I filled up with Shell yesterday, two minutes out of the station and the CEL went off

[Ramblin Fever]

Yeah, you're all thinking the truck's possessed aren't you??

Me too!

It's weird, but it's working!

Just have to make sure she gets Shell, I guess - picky gosh darn son-of-a-gun!!

[Gizmo42]

Have you tried a new gas cap? Dont know what that would have to do with a P0401 code but usually a CEL right after fill up will have something to do with the gas cap. Though I filled mine y'day with the engine running and never got a CEL.

It does seem odd that it only does it with another brand of gas, could just be that that is the time the cap decides not to seal.

I also use shell as my primary brand. I always used texaco when possible, now that shell bought out texaco I use it. I will use conoco if shell isnt around or if I'm in a hurry (there's a conoco right next to where I live).

I get to use 85 octane in mine though with no problems. Even at 12k ft it runs fine with it.

[Ramblin Fever]

Originally Posted by Gizmo42

I get to use 85 octane in mine though with no problems. Even at 12k ft it runs fine with it.

I wish!

Supposedly you're supposed to be able to run lower octane at higher elevation, but tell that to my engine !

Seriously, mine has pinged since the day I bought it with 11k miles if I run anything lower then 87 in high elevation, and in low elevation, I have to run 91 octane or it pings badly.

We did everything when we first bought it to try and figure it out, i.e. new plugs, coil packs, reset the computer 20 times (seriously), upgraded computer programming (per what the dealer said, think they just retarded the timing); tried several different gas stations, fuel filters, dumped fuel charcoal canister, you name it we tried it.

As, when we lived in Las Vegas the truck pinged BADLY on even the slightest incline with 87 octane (that's the lowest octane you can get in the flat-land); after running several tanks of 91, it lessoned up a slight bit, but nothing to justify the cost difference.

The only thing that cured the ping - moving to high elevation, doesn't make sense I know, as the air's thinner and most vehicles ping more here, but not mine, quiet as a mouse now - still have to use 87 though, or the pinging comes back but only lightly.

Don't like to hear it pinging though, so I'll feed it 87.

I do think it got "used" to 87 for so long - we lived in Vegas for the 1st 5yrs/70k miles of it's life, and when we moved here and tried 85 octane, it ran terrible on it, not just pinging but it used a lot more gas and started blowing black smoke after a few weeks, it was weird.

No, I haven't purchased a new fuel gap, as I was hinted that it would have nothing to do with the CEL code I was getting and figured why waist the money. The seal on the gas cap looks ok, but if I get this code coming again, I will try a new cap 1st before buying a new EGR valve itself - as emissions for this beast is coming up soon.

We had an old '79 Chevy 350 p/up that pinged horribly too - but only at sea-level, which confused the hell out of us as well. Vehicles supposedly are suppose to ping more and have a harder time breathing/running in high altitude, but these two vehicles LOVE the elevation.