Low idle and code P0442

[jshaw5]

I've had my 2005 Yukon Denali for a week and a half now, and I have my first issue(s). I've noticed over the past few days that the engine has been idling really low, at like 600 rpm. I've also noticed that if I'm cruising at low rpm's giving it just a little bit of gas, sometimes it stumbles a bit. It goes away if I let off the gas or give it more gas. So far I'm leaning towards the idle air control valve as the culprit.

The check engine light just came on last night with the code P0442. So far most of the research points to a loose or faulty gas cap on that one, but it seems coincidental to get two problems at once.

Is there possibly a more probable solution that solves both issues at once?

 

[ccapehartusarmyINF.(ret)]

okay i am the foremost expert on evap emissions i fought with mine for 6months eventually i wound up replacing every single part of it
evap emissions problems will not cause any driveability issues
you have two seperate issues now for the low idle id start by taking apart yer intake tube cleaning yer MAF and for the evap code a quick and easy way to tell if its your gas cap is when you tighten it does it take some effort before it starts clicking if it does its good if it takes almost no effort before it clicks then replace the gas cap

---------- Post added at 08:27 PM ---------- Previous post was at 08:26 PM ----------

if you got a bad gas cap replaced clear the code you can do this either with a scantool or by disconnecting the battery for like 5 min

---------- Post added at 08:29 PM ---------- Previous post was at 08:27 PM ----------

and before the evap system is tested again the drive cycle for that test has to complete wich its rediculous for that test itll take awhile

 

[Swinger]

okay i am the foremost expert on evap emissions i fought with mine for 6months eventually i wound up replacing every single part of it
evap emissions problems will not cause any driveability issues
you have two seperate issues now for the low idle id start by taking apart yer intake tube cleaning yer MAF and for the evap code a quick and easy way to tell if its your gas cap is when you tighten it does it take some effort before it starts clicking if it does its good if it takes almost no effort before it clicks then replace the gas cap

---------- Post added at 08:27 PM ---------- Previous post was at 08:26 PM ----------

if you got a bad gas cap replaced clear the code you can do this either with a scantool or by disconnecting the battery for like 5 min

---------- Post added at 08:29 PM ---------- Previous post was at 08:27 PM ----------

and before the evap system is tested again the drive cycle for that test has to complete wich its rediculous for that test itll take awhile

I have the same issue... I replaced the gas cap and it came back. I read that it affects nothing with the car and is just another annoyance that these new cars have for the dealers to charge money to fix. I just turn the light off with an obII tester and it comes back on maybe once or so every couple thousands miles. The gas cap did not fix the problem for me

 

[ccapehartusarmyINF.(ret)]

okay since youve eliminated the cheapest part no you can either go to a shop and have them test the evap system with a smoke machine start replacing evap parts there pretty cheap
after the gas cap you need to change the vent valve solenoid its a little boxy lookin thing directly above the rear differential and while yer ordering that you mite as well get a new purge solenoid witch is on top of the throttle body also make sure the evap hoses arent clogged and then if replacing those dosent fix it theres a big box next to the tank thats your charcoal filter its unlikely but that could have been contaminated with fuel at some point and

 

[jshaw5]

So far I've replaced the gas cap and the vent valve solenoid. I was going to order the purge solenoid today. If one of those was the issue, any idea how long it takes for the system to realize that the problem is solved?

For the idle issue, I picked up a can of MAF cleaner, I'll clean that up when my Air Raid comes in.

 

[Swinger]

So far I've replaced the gas cap and the vent valve solenoid. I was going to order the purge solenoid today. If one of those was the issue, any idea how long it takes for the system to realize that the problem is solved?

For the idle issue, I picked up a can of MAF cleaner, I'll clean that up when my Air Raid comes in.

I replace both the purge and vent valve solenoid and then cleared the codes with an OBDII tester. It will take awhile to clear the codes on their own if you don't manually do it. You could also just unplug the battery and they will reset. If those don't work, you might have a leak in the hose that connects both the purge and the vent solenoid. I have read a few other places that the only way to know this is by getting a smoke test done to see where the leak is