installed a new gas cap but still getting code P0440 (evap emission control system malfunction).

suggestions on what else to check?

thanks in advance.

Tom

Did you clear the code and then the code came back?

I should have said that i recently installed a new gas cap. I just got the P0440 code today. I cleared the code and ran the engine again and did not get the code again. Hopefully, it was just a burp.

Good deal! Thanks for letting us know.
Let'* hope the 0440 code stays off & it was just a burp, more like the gas cap seal!
Feel free to post back in the event it re-appears.

OK, I had this issue with my 98. The gas cap had been replaced with an aftermarket by the previous owner. The code appeared again with me. I replaced aftermarket with an ACDelco cap. The problem would still show up at times. If it does the same with you then this is what you need to check. Check the rubber hoses; or replace them, at the purge valve; this is easy to get to on this car. Didn't fix it for me so I kept digging. I found that the hoses at the charcoal canister were bad. You have to remove the air intake box and the computer out of the way to get to these lines. Replacing them fixed my issue. If you do that and still see an issue then you have to look at the lines to the tank; which is a real PITA of course and will mean dropping the tank.

Also, I would guess that a crack in the charcoal canister would also cause this to happen. Basically it is lost of vacuum to the purge system so bad hoses are the first to check for and as I said, cracked hoses at the canister was the cause for me.

I have replaced a lot of purge valves.....

Yes, and I came close to considering that; although tests showed it was doing the job. Easy enough to test these. However, as I stated, it was the rubber hoses; mostly the ones under the computer at the fender well.

All these posts are just SUGGESTIONS.......

If you want to know EXACTLY what to replace, you seal the system and add pressurized smoke.....in other words, a smoke test....

Hey hey, it is all good. Here, have a cold one on me.

The reason I posted is that when I kept getting the problem I never saw anyone mention the rubber lines over at the canister and I did a lot of searches on the net. While it is not a major issue, it will keep you from getting your car inspected in most states if not all. You see the metal line going over there and then it disappears. You have to remove the computer out of the way. I just wanted the OP to know there were some rubber lines over at the canister that can be a problem. On older vehicles these rubber lines break down.

The gold of this forum is that we get feedback on "what fixed it for me" that you don't always get in repair manuals and such. That is gold when it comes to trying to figure out what is wrong with modern autos. It took me months before a mechanic in Cali told me that code 18; check your coil packs. The freaking GM service manual and calls to GM didn't tell me that, it was someone that had experienced it and recorded it and I did a lot of searches on the net and posted to this forum.