Ok, I am about to give in and take my wife's Blazer to the shop.

Here's the story...
August of 2008- wouldn't start, diagnosed bad fuel pump. Changed the fuel pump with a ACDelco unit. Has been great ever since, no codes or other problems.

October 2009- SES light on for EGR valve. Changed it, cleared codes, everything good.

December 2009- SES light on for Evap. Guy at Autozone said to check the gas cap, clear the code and see what happens. Made sense at the time since we just made a day trip and I filled up. Tried that, light still on. Took it back, they scanned it for Evap again, bought a new gas cap, cleared the code, threw a P0452 again. I left it alone until this week.

Feb 2010- changed the Tank Pressure sensor and while I was at it, changed the purge vavle solenoid. I cleared the code and took it for a 60 mile drive. Started it back up this morning and bam, the light is still on.

I am going nuts over this. I hate to see that light on!

The only other thing I know to do is drop the tank again and check the seal. I do not want to give in and take it somewhere. One, because I am cheap and two, because I want to fix it myself.

I have serached the forum for P0452 and there is nothing in those posts that anyone has posted that I haven't tried.

2000 4x4 100,700 miles.

Thanks

 

If you have tried everything, then the next step would be a shop. They can run a smoke test which should identify where the leak is.

 

Ok, took my wife's Blazer out for kicks and giggles just to see if the light decided to go off by itself. Of course, it didn't.

When I got back home and pulled in the garage, I shut it off and heard that loud whistling noise again. I promptly crawled under to hear where it was coming from. It was coming from the tank. Then, I looked at the tank and it was sucked in! It was so sucked in that I could see between the support straps and the bottom of the tank. This concerns me. However, I think the problem is excessive vacuum and not a leak. What could be causing this? I unscrewed the cap and there was a 'woosh' and the tank released and went back to shape.

Help, help, help. I don't want her driving it like this.

Thanks!

 

You have a vent problem with your tank. It isn't venting.

 

Where is it supposed to get its vent from? Evap canister?

 

The vent solenoid (search for "vent+solenoid") is located back near the tank. Sounds like it has failed shut. You could have a problem with the tank pressure sensor not seeing the vacuum that is being applied to the tank from the EVAP purge solenoid (on the engine) and commanding it to be open all of the time...

You really need to diagnose the problem though. I would start with a scan tool to see what the tank pressure sensor is reporting as well as the states of the purge and vent solenoids.