Found this on the vw forums:
I've had the p1582 code for a couple weeks now no other codes just the one. My car was getting poor gas mileage and performance suffered a little, but not too significant. I've done the basics (cleaning tb, reseting tps, cleaning maf) to try and clear it, but nothing helped. So what should I do now?
The p1582 from my understanding means, that the computers limit to adapt to my idle's air fuel ratio
has been reached. So at idle my engine is running too rich or too lean for my computer to keep up with. I took a look at my short term and long term fuel trims to find that my engine was running very rich at idle, knowing that I need to solve the problem before my cat is damaged and I would have to buy a new one.
Ok so what would cause a rich mixture at idle only and only give me one code? Well since I only had one code I assumed all my comprehensive components were fine, so I moved on to looking for vacuum leaks.
At idle the throttle should be closed and no air should be getting into the engine causing a large amount of vacuum or an absence of ambient pressure (outside air). So this means "unmetered" air is getting into my engine with the throttle closed, causing my computer to try to adapt to all this air by leaving the injectors on longer adding more fuel.
Okay, so where is all this air coming from?
I tried my best to find any possible vacuum leaks in the engine bay, but finding vacuum leaks isn't my speciality. So one of my buds who owns a shop said he would hook up a smoker to it. These smokers are amazing which is why they cost 3,500 or more, not too many people have access to these. We disconnected the brake booster
hose from the throttle body
and attached the smoker hose to the vacuum port, turned the smoker on and watched........ nothin.......wtf......there was no smoke coming out of any unusual areas of the engine bay. So at this point I'm getting kinda frustrated, until I noticed smoke coming from the passenger side of the car infront of the rear tire. We lifted the car and there it is a huge leak in my evap system. The leak was about three or four holes punched into a plastic vacuum line, yup plastic
, coming from my fuel tank to the evap purge valve. I cut the hose and added a rubber hoseto connect the two ends that were cut and bam! no more vacuum leak. After three consecutive trips the code was cleared.
Now I'm not saying this is the solution to any p1582 problem, you might get another code thats paired with the p1582 and that would be helpful because it can tell you which specific sub system is causing the p1582.
In my case i only had the one code which isn't very specific because the vacuum leak didn't cause any components to send abnormal inputs to my computer until the computer could no longer keep up with the engines air/fuel mixture at idle.
I hope this was helpful to at least one person, if you have any air/fuel problems that might be the cause of a vacuum leak I would definitely check out those plastic vacuum hoses
that are UNDER the car EXPOSED to the HAZARDS of the road.